ALBERT

Description: Highlights • Coupled geomicrobiology and geomechanics to investigate alterations in shales. • Microbial process can alter the mechanics, mineralogy, and microstructure of shales. • Biogeomechanical alterations reduced permeability by 93% and porosity by 38%. • Microfractures in shales can be sealed during biogeomechanical alterations. • Biogeomechanical alterations can enhance CO2 storage security and caprock integrity. Shales have been a major focus of the energy industry over the past few decades. Recently, there is a paradigm shift in the energy industry to low-carbon solutions, such as carbon capture and storage (CCS), to mitigate global warming caused by carbon footprint. The problem of long-term safe and efficient geological CO2 storage (GCS) and caprock integrity are some of the major challenges impeding large-scale CCS application. Here, we investigated how localized and bulk biogeomechanical alterations could potentially impact caprock integrity and CO2 storage in depleted shale reservoirs. We cultivated the shale core samples (containing both artificial-induced and pre-existing natural fractures) with a cultured microbial solution at specific temperature, time, and growth conditions. Subsequently, we obtain the properties of the fractured shale rock samples impacted by this microbial process. We investigate the impact of the mechanical responses due to the microbial process, on the long-term integrity and storage potentials of CO2 in shale reservoirs. Our results suggest that in Eagle Ford, Marcellus, and Niobrara shale formations, microbially-altered local and bulk mechanical properties can enhance the long-term caprock integrity and CO2 storage security by: (1.) Increasing the localized (+19% unconfined compressive strength, −20% Poisson’s ratio, +35% fracture toughness) and bulk (+50% unconfined compressive strength, −13% Poisson’s ratio) mechanical integrity; (2.) Decreasing permeability (−93%) and porosity (−38%); (3.) Altering the clay mineral content (−56%), calcite content (+21%), and morphology; (4.) Occluding microfractures; and (5.) Mitigating any potential leakage to the atmosphere through the caprock. This study considers the heterogeneity of shales, and provide valuable insights and viable assessment in solving the long-term GCS application in depleted hydrocarbon reservoirs.

Description: In the present work, an untargeted metabolomic approach based on ultra-high-performance liquid chromatography coupled with high-resolution mass spectrometry (UHPLC–HRMS) was performed for the discrimination of 25 accessions of white quinoa from main production zones of Peru. From the fingerprint analysis, a total of eighty-four metabolites were tentatively identified based on their accurate mass measurements and MS/MS data. Among them, forty-six compounds are reported here for the first time in C. quinoa (eight phenolics, one ecdysteroid, and thirty-seven saponins), twenty-four of them would correspond to new structures. Principal component analysis (PCA) and orthogonal partial least square discriminant analysis (OPLS-DA) were used to analyze the metabolomic data. As a result, the samples were distributed into two groups. The compounds contributing to the differences between these groups were identified by S-plot analysis.

Description: Highlights • UAV-based thermal imaging allows precise mapping of diffusive thermal water discharge. • High tidal ranges affect fluid flow and promote larger thermal anomaly. • The La Jolla thermal anomaly is caused by a discharge of 330 ± 44 L s−1 of thermal water. • The La Jolla advective heat output (40.5 ± 5.2 MWt) can power a desalinization plant. The exploration of unexploited geothermal resources is required to encourage the use of renewable energy. This study focuses on La Jolla beach, Ensenada, Mexico. The beach hosts a thermal anomaly with temperatures of up to 52 °C at the surface and up to 93 °C at 20 cm depth. The objectives were to: map the thermal anomaly, understand the impact of tides, quantify the thermal water discharge rate and heat output, and discuss a direct use of the energy. The mapping was performed with Unmanned Aerial Vehicles equipped with optical and thermal cameras at two different dates. Additional temperature measurements were performed with a thermocouple, while the total fluid discharge was estimated from flow measurements. A comparison between the campaigns indicated that the highest surface temperature area was more than three times larger in 2019 than in 2018 (259 m2 vs. 69 m2). Such change was due to the tidal range and associated hydrostatic pressure variations. The total thermal water discharge is 330 ± 44 L s−1, which corresponds to an advective heat output of 40.5 ± 5.2 MWt. The use of this energy in a Multi-Effect Distillation desalinization plant can contribute to cover the shortage of freshwater in Ensenada.

Description: The Neolithic Revolution began approximately 10,000 years ago and is characterized by the ultimate, nearly complete transition from hunting and gathering to agricultural food production on land. The Neolithic Revolution is thought to have been catalyzed by a combination of local population pressure, cultural diffusion, property rights and climate change. We undertake a thought experiment that examines trends in these key hypothesized catalysts of the Neolithic Revolution and patterns of today to explore whether society could be on a path towards another paradigm shift in food production: away from hunting of wild fish towards a transition to mostly fish farming. We find similar environmental and cultural pressures have driven the rapid rise of aquaculture, during a period that has now been coined the Blue Revolution, providing impetus for such a transition in coming decades to centuries (as opposed to millennia). However, we also highlight the interacting and often mutually reinforcing impacts of 1) technological and scientific advancements, 2) environmental awareness and collective action and 3) globalization and trade influencing the trajectory and momentum of the Blue Revolution from patterns and processes of the Neolithic Revolution. We present two qualitative narratives that broadly fall within two future trajectories of seafood production: 1) a ubiquitous aquaculture transition and 2) commercial aquaculture and fisheries coexistence. Each narrative contains two sub-narratives based on differing management and regulatory strategies for aquaculture and fisheries. This scenarios approach aims to encourage logical, forward thinking, and innovative solutions to complex systems’ dynamics. Scenario-based thought experiments are useful to explore large scale questions, increase the accessibility to a wider readership, and ideally catalyze discussion around proactive governance mechanisms. We argue the future is not fixed and society now has greater foresight and capacity to choose the workable balance between fisheries and aquaculture that supports economic, environmental, cultural and social objectives through combined planning, policies, and management.

Description: Highlights • Coupled microbiology and geomechanics to investigate alterations in shales. • Microbial process can alter the near-wellbore of shale gas reservoirs. • Microbial alterations of near-wellbore rock properties can weaken mechanical integrity. • Biogeomechanical alterations increased porosity (+42%) & permeability (+6430%). • Biogeomechanical alteration with other stimulation methods can improve gas recovery. Shale gas reservoirs, with typically ultra-low permeabilities, have been a major focus of hydrocarbon production over the past few decades. In this paper, we investigated how biogeomechanical alteration of near-wellbore properties could potentially impact hydrocarbon recovery from low-permeability reservoirs, using Wolfcamp shale and Niobrara shale formations. We first obtained the geomechanical properties using the scratch test method, in addition to the mineralogical, microstructural, and porosity and permeability measurements of the shale gas samples. Subsequently, we treated the core samples with a cultured microbial solution at distinct conditions. Further, we obtained the corresponding new geomechanical properties, in addition to the new mineralogical, microstructural, and porosity measurements of the samples impacted by the process. Finally, we showed the implications of the altered near-wellbore properties for hydrocarbon recovery from shale gas reservoirs. Our results suggest that in shale gas reservoirs, microbial-induced alterations of near well-bore properties could temporally reduce its mechanical integrity (Wolfcamp shale = −21% unconfined compressive strength, −42% scratch toughness; Niobrara shale = −24% unconfined compressive strength, −14% scratch toughness), increase porosity (+43%) and permeability (+6430%), and impact the microstructural and mineralogical properties. The near-wellbore biogeomechanical alterations could potentially improve hydrocarbon recovery by enhancing: (1.) the susceptibility for induced fractures to nucleate and propagate during reservoir-stimulation; (2.) flow pathways to improve hydrocarbon recovery.

Description: Both chemical and isotopic compositions of volcanic plumes are highly useful in evaluating the present status of active volcanoes. Monitoring their temporal changes can facilitate the forecasts of volcanic activity as well. In the present study, we developed a drone-borne automatic sampler for volcanic plumes in which an output signal from a sulfur dioxide (SO2) sensor triggered a pump to collect samples when its SO2 concentration exceeded a predefined threshold. First, we tested the automatic sampler while holding the device by hand at Iwo-yama volcano, Kirishima volcanic complex, Japan, where the fumaroles were accessible. Second, we fitted the sampler on a drone at Nakadake central cone, Aso volcano, Japan, where only the crater rim was accessible. In both sampling campaigns, good consistency in isotope ratios (2H/1H) of molecular hydrogen (H2) between samples collected by the automatic sampler and those collected directly into pre-evacuated flasks was obtained. Furthermore, by using the drone-borne sampler at Aso volcano, we obtained plume samples with higher concentrations of H2 and carbon dioxide than those taken directly into flasks at the crater rim. Our sampler can be utilized to collect volcanic plume samples for the determination of stable isotopic compositions in general by subsequent laboratory analysis and the remote establishment of fumarole outlet temperature based on the 2H/1H ratios of hydrogen, including their temporal changes.

Description: Volcaniclastic stratigraphy can be difficult to map and describe due to its complex nature. However, such stratigraphy preserves information about fluctuations in volcanic activity and sedimentation and is vital to understanding volcanic systems. Uncrewed aerial vehicle (UAV) based analysis of volcanic stratigraphy can enhance mapping and analysis, especially on vertical surfaces where outcrop exposure is greatest. Here we present a method for using small UAVs to produce vertical grain size and bedding measurement logs, or quantitative stratigraphic columns, of vertical volcaniclastic stratigraphy. We demonstrate the range of high-accuracy measurements and parameters that can be collected for building measurement logs using consumer grade UAVs through a case study in the Marysvale volcanic field where we collected 34,422 grain measurements from 21 individual units. The purpose of producing such measurement logs is to enhance lithofacies analysis through the use of large quantitative datasets and improve the reproducibility of data reporting. Whereas descriptions of volcaniclastic units such as those describing grading are often reported qualitatively, we describe methods for calculating numerical parameters for enhanced lithologic analysis including grain size, grading, clast to matrix ratios, and shape characteristics. The methods described in this paper can enhance field data acquisition, mapping, and quantitative analysis of volcaniclastic deposits and are applicable to a wide range of other geologic settings where coarse-grained clastic sedimentary deposits exist.

Description: Highlights: • Temperature anomalies for the Mid-Holocene compared to preindustrial are significantly different in the low- and high-resolution versions of the atmospheric model ECHAM5 • For summer, shortwave cloud radiative forcing emerges as an important factor. • For boreal winter, differences are mainly related to circulation changes. • Anomaly differences are regionally as large as the mid-Holocene minus preindustrial temperature signals. Abstract: This study evaluates the dependence of simulated surface air temperatures on model resolution and orography for the mid-Holocene. Sensitivity experiments with the atmospheric general circulation model ECHAM5 are performed with low (∼3.75°, 19 vertical levels) and high (∼1.1°, 31 vertical levels) resolution. Results are compared to the respective preindustrial runs. It is found that the large-scale temperature anomalies for the mid-Holocene (compared to preindustrial) are significantly different in the low- and high-resolution versions. For boreal winter, differences are mainly related to circulation changes caused by the response to thermal forcing in conjunction with orographic resolution. For summer, shortwave cloud radiative forcing emerges as an important factor. The anomaly differences (low minus high resolution version) in the Northern Hemisphere are regionally as large as the anomalous mid-Holocene temperature signals. Furthermore, they depend on the applied surface boundary conditions. We conclude that the resolution matters for the Northern Hemisphere response in mid-Holocene simulations, which should be taken into account in model-model and data-model comparisons.

Description: Highlights • UAV surveys can be used for evaluating long-term hillslope morphology evolution. • Successive landslides influence frequency distributions of topographic features. • Successive landslides gradually reduce slope gradient, roughness and local relief. • The slope gradient changes with elevation. Landslides are recognized as dominant geomorphic events of morphological evolution in most mountainous and hilly landscapes. However, the lack of multitemporal high-resolution topographic data has resulted in a lack of quantitative estimates of topographic changes influenced by successive landslides. Taking a typical hillslope with successive loess landslides in the Heifangtai loess tableland, China, as an example, we conducted four unmanned aerial system (UAS) surveys and created corresponding high-resolution digital elevation models (HRDEMs) and orthophotos. We found that multitemporal UAS surveys have become a powerful new approach for addressing local topographic changes and evolution over a relatively long time series. Moreover, landslides can leave persistent geomorphic imprints on hillslope topography. The frequency distributions of topographic indexes are significantly influenced by successive landslides. The mean slope gradient, roughness and local relief decreased with successive landslide occurrences, whereas the mean topographic wetness index (TWI) increased. However, the mean slope aspect was almost unchanged by successive landslides. Furthermore, analysis of the coefficient of variation demonstrates that the frequency distribution of the slope gradient becomes more dispersed with landslide occurrences, while the slope aspect and TWI become more concentrated. The slope gradient changes with elevation. More broadly, this study provides new insights into the prediction of the local topographic feature changes and morphology evolution trends caused by successive landslides.

Description: Highlights • Shale samples were exposed to slick water under the condition of 120 °C and 20 MPa within 30–90 days. • Microindentation was conducted to probe the distance-dependent, gradient alteration to shale mechanical properties. • The average rate of softening advancement was estimated as 0.13 mm/day. • The dissolution of carbonate minerals, pyrite oxidation and clay mineral osmotic swelling determine the shale softening. The shale softening behavior caused by hydrofracturing fluid is of great influence for the fracture conductivity and ultimate recovery of oil and gas from reservoir formations. This paper presents an experimental study on the characterization of a shale after being softened by the coupled thermo-hydro-mechanical-chemical (THMC) treatments that simulate the high-temperature and high-pressure rock-fluid interactions occurring in deep reservoirs during and after hydraulic fracturing. Microindentation tests were conducted to characterize the degradation degree and rate of mechanical properties of THMC-treated samples, and X-ray diffraction (XRD), scanning electron microscope (SEM), and micro-computed tomography (micro-CT) were carried out to analyze compositional and microstructural alterations of samples prior to and after THMC treatment. The results show that Young's modulus, hardness, and fracture toughness degrade significantly upon THMC treatment, and the average softening rate was estimated as 0.13 mm/day. The degradation of mechanical properties of the softened zones is primarily owing to the porous microstructure and crack propagation, resulting from the dissolution of carbonates, pyrite oxidation and the clay mineral osmotic swelling. These findings can provide a good insight of shale-fracturing fluid interactions, phenomenological behavior of shale softening that take place in deep reservoirs at elevated temperatures and pressures, and shed lights on the design, and operation of shale gas exploration.

Description: The recent and growing development and availability of unmanned aerial vehicles/systems (UAV, UAS, or “drones”) in volcanology has promoted a significant advance in volcanic surveillance of active volcanoes and in the characterization of volcanic landforms and hazards. However, in the tropics with heavy rainfall, deep volcanic soils and high relief, UAV surveying for volcanic geomorphology and volcanic hazards seems to be a relatively unexplored technique. Our aim is to present and promote innovative low-cost (〈$3000) UAV applications in volcanology to reduce costs and improve high-resolution quality (up to 8 cm/pixel) data acquisition in highly dynamic landscapes. Our results contribute to the state of the art of UAV applications in volcanic landforms in tropical developing countries where nearly half of the globally active volcanoes are located. Our findings prove that UAV's are a low-cost technique that can map large extensions of geomorphological features with accessibility limitations due to geological hazards and/or private property restrictions in short time. We surveyed four active volcanic sites in Costa Rica, Central America to illustrate potential applications of UAV mapping and geomorphological analysis of lava flows, debris avalanches, lahar deposits (debris flows) and biogeomorphic landscape changes due to forest succession. Analysis derived from the digital imagery captured by the UAV allowed to determine accurate volume calculations, surface roughness characteristics, morphometric quantifications, supervised surface classifications, and in combination with hydraulic modelling to assess hazards in urban planning. We discuss the utility, limitations, and future directions of low-cost UAV surveying in the geomorphological and geological analysis of tropical volcanic landforms and processes.

Description: Mount Agung (the highest volcano in Bali, Indonesia) began to erupt on November 21, 2017, after having been dormant for 53 years. More than 100,000 people were evacuated within the hazard zone between September 2017 (when the highest volcanic alert was issued) and early 2018. The eruptions continued until June 2019, accompanied by at least 110 explosions. During the eruptive crisis, the observation of the lava dome's emplacement was essential for mitigating the potential hazard. Details of the lava dome growth, including the volumetric changes and effusion rates, provide valuable information about potential eruption scenarios and lahar depositions. In this paper, the essential role of multi-temporal unmanned aerial vehicle (UAV) images in the monitoring of Mt. Agung's lava dome, and in determining the areas of potential lahar hazards during the crisis between 2017 and 2019 is described. A fixed-wing UAV was launched outside the hazard zone to photograph the lava dome on five occasions. Image enhancement, machine learning, and photogrammetry were combined to improve image quality, remove point clouds outliers, and generate digital terrain models (DTMs) and orthoimages. The analysis of the obtained DTMs and orthoimages resulted in qualitative and quantitative data highlighting the changes inside the crater and on the surrounding slopes. These results reveal that, from November 25 to December 16, 2017, the lava dome grew vertically by 126 m and reached a volume of 26.86 ± 0.64 × 106 m3. In addition, its surface experienced a maximal uplift of approximately 52 m until July 2019 with the emergence of a new dome with a volume estimated at 9.52 ± 0.086 × 106 m3. The difference between the DTMs of 2017 and 2019 reveals the total volume of erupted material (886,100 ± 8000 m3) that was deposited on the surrounding slopes. According to the lahar inundation simulation, the deposited material may cause dangerous lahars in 21 drainages, which extend in the north (N), north-east (N-E), south (S), south-east (S-E), and south-west (S-W) sectors of the volcano. This paper presents the use of UAV remote sensing for the production of high-spatial resolution DTMs, which can be used to both observe the emplacement of a lava dome, and to identify areas with potential lahar risk during a volcano crisis.

Description: Highlights • A new approach using UAS to map and classify volcanic deposits is described. • Tephra and lava are distinguished by their roughness and solar heating rate. • Solar heating rate decreases as lava transitions from pāhoehoe to ʻaʻā. • We compare manual and machine learning classification methods. The deposits from volcanic eruptions represent the record of activity at a volcano. Identification, classification, and interpretation of these deposits are crucial to the understanding of volcanic processes and assessing hazards. However, deposits often cover large areas and can be difficult or dangerous to access, making field mapping hazardous and time-consuming. Remote sensing techniques are often used to map and identify the deposits of volcanic eruptions, though these techniques present their own trade-offs in terms of image resolution, wavelength, and observation frequency. Here, we present a new approach for mapping and classifying volcanic deposits using a multi-sensor unoccupied aerial system (UAS) and demonstrate its application on lava and tephra deposits associated with the 2018 eruption of Sierra Negra volcano (Galápagos Archipelago, Ecuador). We surveyed the study area and collected visible and thermal infrared (TIR) images. We used structure-from-motion photogrammetry to create a digital elevation model (DEM) from the visual images and calculated the solar heating rate of the surface from temperature maps based on the TIR images. We find that the solar heating rate is highest for tephra deposits and lowest for ʻaʻā lava, with pāhoehoe lava having intermediate values. This is consistent with the solar heating rate correlating to the density and particle size of the surface. The solar heating rate for the lava flow also decreases with increasing distance from the vent, consistent with an increase in density as the lava degasses. We combined the surface roughness (calculated from the DEM) and the solar heating rate of the surface to remotely classify tephra deposits and different lava morphologies. We applied both supervised and unsupervised machine learning algorithms. A supervised classification method can replicate the manual classification while the unsupervised method can identify major surface units with no ground truth information. These methods allow for remote mapping and classification at high spatial resolution (〈 1 m) of a variety of volcanic deposits, with potential for application to deposits from other processes (e.g., fluvial, glacial) and deposits on other planetary bodies.

Description: Highlights: • Wind-PV power mix beneficial for balancing variability due to weather. • Ratio of 45–57% for PV over PV plus wind power maximises balancing effects. • Simultaneous extremes in wind and PV power occur on less than 10% of the days. Abstract: The increasing use of wind and solar power requires interventions to balance the associated variability in energy production. One option to reduce the costly interventions is to exploit the natural de-correlation of wind and irradiance. This study characterises the balancing potential of the natual variability in wind and photovoltaic energy production within and across eleven European countries. We use 20 years of highly resolved meteorological data from a post-processed regional reanalysis with a 6 km horizontal grid to calculate daily photovoltaic and wind power. Our results suggest a country-dependent reduction of the day-to-day variability in energy production by 29%–42% due to installing both PV and wind power capacities, compared to wind power only. The optimized photovoltaic to photovoltaic plus wind power generation ratios are 45–57% for maximizing balancing effects associated with the changing weather. We further identify on less than 10% of the days a simultaneous occurrence of extremes in photovoltaic and wind power across European countries. The cross-border balancing potentials for the extremes in renewable energy production are therefore high due to the spatio-temporal differences of the local weather.

Description: Highlights • Shear strength in the BPT is estimated based on tensorial strain partitioning. • Accounting for full strain components resolves problems in the two-mechanism model. • Inclination of slip planes causes weakening relative to the friction law. • Fault-parallel compression is significant in the BPT and brittle regimes. A constitutive law of shear zones in the brittle-plastic transition (BPT) is of great importance to understanding loading at the bottom of the seismogenic layer preceding large earthquakes. Previous microphysics-based models are based on the partitioning of slip and dilation normal to the shear zone into different deformation mechanisms. Here, I account for the remaining 2-D strain component, inelastic extension of the shear zone, and associated stress buildup parallel to the shear zone, and investigate the steady-state behavior of a shear zone in which slip on inclined planes and bulk plastic flow coexist. Kinematic constraints and constitutive laws of the two mechanisms were solved numerically. The results show that the inclination of slip planes causes weakening relative to the friction law. Whereas the previous two-mechanism model yields a larger strength than the friction law for a rate-weakening slip element in the BPT, the present model qualitatively resolves this problem. Fault-parallel compression buildup can exceed the normal stress in the BPT and the brittle regime if the friction coefficient of the slip planes is in the range of Byerlee's law. This study illuminates the importance of fault-parallel compression in understanding the fabrics and strengths of shear zones.

Description: Degassing volcanic systems, expressed by fumaroles, thermal anomalies, and hydrothermal alteration and deposition at the surface provide insights into the underlying structural architecture and the magmatic system. While the fumarole sites are easily identified and investigated, areas of diffuse degassing and associated hydrothermal alteration are barely explored. Here we investigate high-resolution optical and thermal infrared (TIR) data, acquired by unoccupied aircraft systems (UAS) at the La Fossa cone (Vulcano Island) in November 2018. The data provides insights into the structural complexity of degassing sites and associated processes at the surface. Applying the Structure from Motion (SfM) approach, we generate a photomosaic database with a 0.05 m and 0.7 m pixel resolution for the optical and infrared datasets, respectively. A Principal Component Analysis (PCA) was applied to the optical data to detect, define and extract areas of hydrothermal alteration and sulfuric deposition on a pixel base, with a feature detection threshold of up to 25 cm2. By comparing optical data, PCA results and the IR data, we found a broad alteration zone dominated by diffuse degassing surrounding the main fumaroles, which with ~ 60,000 m2 is ten times larger than the area covered by fumaroles and yellowish sulfuric deposits. Spectral and thermal characteristics of this alteration zone suggest a segmentation into at least 13 distinct subregions. Hydrothermal alteration and deposition were analyzed considering their pixel density and spectral signature (RGB) and show the highest pixel density in the center of the fumarole field, accompanied by a systematic color shift. The same region is characterized by a systematic change in azimuths of thermal lineaments and sulfuric clusters from the dominating trend NW-SE by ~90 degrees to NE-SW. We conjecture this to be controlled by a permeability contrast due to a subsurface structure or crater intersection, facilitating a more direct gas ascent in the center of the fumarole field. We provide a precise and complete database for the state and extent of the La Fossa fumarole field, which can be used for comparative monitoring of spatio-temporal changes within the hydrothermal system at the surface.

Description: Highlights • Release of additives from plastic pollution may harm wildlife. • Robust methods to characterise additives and their leaching behaviour are needed. • Extraction and leaching methods are informed from well-established industry methods. • Recommended approaches for extraction and leaching studies are presented. • The use of environmentally relevant methods and test materials is advised. Plastic pollution is prevalent worldwide and has been highlighted as an issue of global concern due to its harmful impacts on wildlife. The extent and mechanism by which plastic pollution effects organisms is poorly understood, especially for microplastics. One proposed mechanism by which plastics may exert a harmful effect is through the leaching of additives. To determine the risk to wildlife, the chemical identity and exposure to additives must be established. However, there are few reports with disparate experimental approaches. In contrast, a breadth of knowledge on additive release from plastics is held within the food, pharmaceutical and medical, construction, and waste management industries. This includes standardised methods to perform migration, extraction, and leaching studies. This review provides an overview of the approaches and methods used to characterise additives and their leaching behaviour from plastic pollution. The limitations of these methods are highlighted and compared with industry standardised approaches. Furthermore, an overview of the analytical strategies for the identification and quantification of additives is presented. This work provides a basis for refining current leaching approaches and analytical methods with a view towards understanding the risk of plastic pollution.

Description: Highlights • Carbon dioxide + propane mixtures are studied through accurate measurements of speeds of sound and phase equilibria. • Heat capacities and virial coefficients are obtained from speeds of sound. • Retrograde condensation zone is found for the (0.60 CO2 + 0.40 C3H8) mixture. • Results are compared with reference equations of state such as GERG-2008 and AGA8-DC92. This work presents phase envelope and speed of sound data for the (0.60 CO2 + 0.40 C3H8) and (0.80 CO2 + 0.20 C3H8) binary mixtures. Phase equilibria was measured using a cylindrical resonator working in the microwave band whereas an acoustic resonator was used for speed of sound measurements. The experimental results were compared with GERG-2008 equation of state, obtaining average absolute deviations by 0.24% in pressure for phase equilibria data and 0.025% for speed of sound data. Speed of sound values were used to derive perfect-gas heat capacities, acoustic virial coefficients, and second density virial coefficients. In addition, AGA8-DC92 equation of state performance was checked for the results derived from speeds of sound.

Description: Most air quality stations in Spain exceeded the European Union's daily PM10 limit due to the February 2016 Saharan dust outbreak, which resulted from two successive dust storms in Northwest Africa. This study identifies the meso-β/meso-γ-scale dynamical processes responsible for developing these dust storms using observations and high-resolution Weather Research and Forecasting model coupled with Chemistry simulations. The results revealed that the first dust storm was associated with a strong barrier jet (BJ). The BJ formed on the southeastern foothills of the Saharan Atlas Mountains (SAM) when an easterly-northeasterly low-level Mediterranean flow was blocked by a stably stratified layer close to the SAM. The BJ intensified just after sunrise on 20 February and the associated near-surface peak winds organized the first dust storm. The second dust storm was linked to a mesoscale gravity wave (MGW) and hydraulic jumps. A long-lived westward propagating MGW was triggered by a downslope flow interacting with the stable layer near the northeastern edge of the Tinrhert Plateau in eastern Algeria. When this MGW crossed the Tademaït Plateau, hydraulic jumps formed on its lee side. The strong winds accompanying these hydraulic jumps formed the second dust storm on 21 February. The lifted dust extended over a depth of 2–3 km in the growing daytime boundary layer and was advected poleward by the southerly/southeasterly mid-tropospheric winds. Our results underline the importance of resolving terrain-induced mesoscale processes to understand dust storm dynamics, which are difficult to represent in coarse-resolution numerical models.

Description: Estimations of the global carbon budget include a quantitative understanding of the evolving processes that occur along river-to-ocean gradients. However, high spatiotemporal resolution observations of these processes are limited. Here we present in situ measurements of the partial pressure of CO2 (pCO2) made through the Amazon River plume (ARP) during different discharge seasons, from 2010 to 2012. We evaluated the spatiotemporal distribution of pCO2 using Soil Moisture and Ocean Salinity (SMOS) satellite observations for each hydrologic period in the ARP. Regression models were used to estimate pCO2 at the ARP for the period of 2010–2014. From these distributions we calculated sea-air gas exchange of CO2 between the plume waters and the atmosphere (Fsea co2). Intra-annual variability of Fsea co2 was related to discharge at the river mouth and ocean currents as well as trade winds in the plume. Climatic events during the study period had a significant impact on the Fsea co2. Including the plume area closer to the river mouth makes the ARP a net source of CO2 with an annual net sea-air flux of 8.6 ± 7.1 Tg C y−1 from 2011 to 2014.

Description: Isocitrate dehydrogenase (IDH) is one key rate-limiting enzyme in the tricarboxylic acid cycle, which is related to various cancers. Tomatillo (Physalis ixocarpa), a special tomato, is widely consumed as nutritious vegetable in Mexico, USA, etc. As a rich source for withanolides, the fruits of P. ixocarpa were investigated, leading to the isolation of 11 type-A withanolides including 4 new ones (1 is an artificial withanolide). All these withanolides were evaluated for their inhibition on mutant IDH1 enzyme activity. Among them, physalin F (11) exhibited potent enzyme inhibitory activity and binding affinity with mutant IDH1. It inhibits the proliferation of HT1080 cells by selectively inhibiting the activity of mutant IDH1. Since Ixocarpalactone A, another major type-B withanolide in this plant, could act on another energy metabolism target PHGDH, the presence of different types of withanolides in tomatillo and their synergistic effect could make it a potential antitumor functional food or drug.

Description: often recognized too late, typically when changing the adopted technologies and behavioral norms is difficult. A similar story may unfold if society continues to blindly transition to an unregulated and environmentally unaudited digital world, a transition path that has been facilitated by the fourth industrial revolution and is now accelerated by the global COVID-19 crisis. The newly developed digital lifestyle has major environmental benefits, including the reduction of travel-related CO2 emissions. Yet, increased Internet use has some hidden environmental impacts that must be uncovered (Fig. 1a) to make the transition to a lowcarbon and green economy successful. The data centers’ electricity consumption accounts for 1% of the global energy demand (Masanet et al., 2020), more than the national energy consumption of many countries. Depending on the energy supply mix and use efficiency, Internet traffic contributes differently to negative environmental impacts and climate change. As the number of Internet users increases, the number of online services and applications they use grow. This trend exacerbates the environmental footprint of the Internet, despite the many successful and significant efforts to improve the efficiency of data centers (Masanet et al., 2020) and reduce their reliance on fossil energy. In order to build a sustainable digital world, it is imperative to carefully assess the environmental footprints of the Internet and identify the individual and collective actions that most affect its growth.

Description: Fucus virsoides and Cystoseira barbata are important sources of sulfated polysaccharide fucoidan which shows a wide range of biological activities. These activities are significantly dependent on chemical composition which is influenced by species, anatomical part of the seaweed, growing location and conditions, extraction procedures and analytical methods. The objective of this study was to evaluate influence of various pre-treatment solvents and conventional extraction parameters (solvent, temperature and time) on polysaccharide yield and chemical composition (total sugar, fucose, sulfate group and uronic acid content) of the fucoidan from F. virsoides and C. barbata. Combination of acetone and ethanol was chosen for pre-treatment since it removed the most interfering compounds and resulted with the highest polysaccharide yield. Applying acid (0.1 M HCl and 0.1 M H2SO4) instead of water for polysaccharide extraction improved yield and resulted with fucoidan with higher sulfate group content, lower uronic acid content but lower fucose content. Extraction at higher temperatures and longer time resulted with higher polysaccharide yield, uronic acid and total sugars content. However, they had the opposite effect on fucose and sulfate group content between F. virsoides and C. barbata.

Description: Background Glioblastoma multiforme (GBM) is the most frequent, lethal and aggressive tumour of the central nervous system in adults. The discovery of novel anti-GBM agents based on the isocitrate dehydrogenase (IDH) mutant phenotypes and classifications have attracted comprehensive attention. Purpose Diterpenoids are a class of naturally occurring 20-carbon isoprenoid compounds, and have previously been shown to possess high cytotoxicity for a variety of human tumours in many scientific reports. In the present study, 31 cassane diterpenoids of four types, namely, butanolide lactone cassane diterpenoids (I) (1-10), tricyclic cassane diterpenoids (II) (11-15), polyoxybutanolide lactone cassane diterpenoids (III) (16-23), and fused furan ring cassane diterpenoids (IV) (24-31), were tested for their anti-glioblastoma activity and mechanism underlying based on IDH1 mutant phenotypes of primary GBM cell cultures and human oligodendroglioma (HOG) cell lines. Results We confirmed that tricyclic-type (II) and compound 13 (Caesalpin A, CSA) showed the best anti-neoplastic potencies in IDH1 mutant glioma cells compared with the other types and compounds. Furthermore, the structure-relationship analysis indicated that the carbonyl group at C-12 and an α, β-unsaturated ketone unit fundamentally contributed to enhancing the anti-glioma activity. Studies investigating the mechanism demonstrated that CSA induced oxidative stress via causing glutathione reduction and NOS activation by negatively regulating glutaminase (GLS), which proved to be highly dependent on IDH mutant type glioblastoma. Finally, GLS overexpression reversed the CSA-induced anti-glioma effects in vitro and in vivo, which indicated that the reduction of GLS contributed to the CSA-induced proliferation inhibition and apoptosis in HOG-IDH1-mu cells. Conclusion Therefore, the present results demonstrated that compared with other diterpenoids, tricyclic-type diterpenoids could be a targeted drug candidate for the treatment of secondary IDH1 mutant type glioblastoma through negatively regulating GLS.

Description: Some trace elements (TE) are eminently toxic for humans (e.g., Al, Pb, Hg, Cd) and its presence in the central nervous system has been linked to the etiology of neurodegenerative diseases (ND). More recently, the focus has shifted to the potential role of the imbalances on essential TE levels (e.g., Fe, Cu, Zn, Se) within the brain tissue, and they have also been identified as potentially responsible for the cognitive decline associated with normal ageing and the development of some ND, although their definite role remains unclear. Accurately, well-defined reference values for TE levels in human body fluids and tissues are indispensable to identify possible disturbances in individual cases. Moreover, since the brain is a highly heterogeneous organ, with anatomically and physiologically very different areas, a detailed mapping of TE distribution across the brain tissue of normal individuals, with an in-depth analysis of TE levels in the different brain regions, is a mandatory prior work so that the results obtained from patients suffering from ND and other brain diseases can be interpreted. This review aims to compile and summarize the available data regarding TE levels in the different human brain regions of “normal” (non-diseased) individuals in order to contribute to the establishment of robust reference values. Fifty-four studies, published since 1960, were considered. The results showed a great variability between different studies. The potential sources of this variability are discussed. The need for increased harmonization of experimental strategies is highlighted in order to improve the comparability of the data obtained.

Description: Highlights: • Ecological impacts of Pontogammarus maeoticus increased with temperature • Salinity effects were non-significant across temperatures (14–2 ppt; 18–22 °C) • Gammarids displayed hyperbolic Type II functional responses in all treatments • Future salinity regime shifts will not lessen ecological impacts via predation • Warming will heighten the ecological impacts of this emerging invasive species Abstract: Biological invasions are a growing ecological and socioeconomic problem worldwide. While robust predictions of impactful future invaders are urgently needed, understandings of invader impacts have been challenged by context-dependencies. In aquatic systems in particular, future climate change could alter the impacts of invasive non-native species. Widespread warming coupled with sea freshening may exacerbate ecological impacts of invaders in marine environments, compromising ecosystem structure, function and stability. We examined how multiple abiotic changes affect the potential ecological impact of an emerging invasive non-native species from the Ponto-Caspian region — a notorious origin hotspot for invaders, characterised by high salinity and temperature variation. Using a comparative functional response (feeding rates across prey densities) approach, the potential ecological impacts of the gammarid Pontogammarus maeoticus towards native chironomid prey were examined across a range of current and future temperature (18, 22°C) and salinity (14, 10, 6, 2 ppt) regimes in a factorial design. Feeding rates of P. maeoticus on prey significantly increased with temperature (by 60 %), but were not significantly affected by salinity regime. Gammarids displayed significant Type II functional responses, with attack rates not significantly affected by warming across all salinities. Handling times were, however, shortened by warming, and thus maximum feeding rates significantly increased, irrespective of salinity regime. Functional responses were significantly different following warming at high prey densities under all salinities, except under the ambient 10 ppt. Euryhalinity of invasive non-native species from the Ponto-Caspian region thus could allow sustained ecological impacts across a range of salinity regimes. These results corroborate high invasion success and field impacts of Ponto-Caspian gammarids in brackish through to freshwater ecosystems. Climate warming will likely worsen the potential ecological impact of P. maeoticus. With invasions growing worldwide, quantifications of how combined elements of climate change will alter the impacts of emerging invasive non-native species are needed.

Description: Highlights: • Predators displayed a Type II functional response towards prey • Microplastics had no effect on predator feeding efficiency • Functional responses are a useful tool for microplastic exposure studies • An environmentally relevant approach is needed in future microplastic exposure studies Abstract: Microplastics may affect the physiology, behaviour and populations of aquatic and terrestrial fauna through many mechanisms, such as direct consumption and sensory disruption. However, the majority of experimental studies have employed questionably high dosages of microplastics that have little environmental relevance. Predation, in particular, is a key trophic interaction that structures populations and communities and influences ecosystem functioning, but rarely features in microplastic research. Here, we quantify the effects of low (~65-114 MP/L) and high (~650-1140 MP/L) microplastic concentrations on the feeding behaviour of a ubiquitous and globally representative key marine predator, the shore crab, Carcinus maenas. We used a functional response approach (predator consumption across prey densities) to determine crab consumption rates towards a key marine community prey species, the blue mussel Mytilus edulis, under low and high microplastic concentrations with acute (8h) and chronic (120 h) microplastic exposure times. For both the acute and chronic microplastic exposure experiments, proportional prey consumption by crabs did not differ with respect to microplastic concentration, but significantly decreased over increasing prey densities. The crabs thus displayed classical, hyperbolic Type II functional responses in all experimental groups, characterised by high consumption rates at low prey densities. Crab attack rates, handling times and maximum feeding rates (ie functional response curves) were not significantly altered under lower or higher microplastics concentrations, or by acute or chronic microplastic exposures. Here, we show that functional response analyses could be widely employed to ascertain microplastic impacts on consumer-resource interactions. Furthermore, we suggest that future studies should adopt both acute and chronic microplastic exposure regimes, using environmentally-relevant microplastic dosages and types as well as elevated future scenarios of microplastic concentrations.

Description: The facies distribution in time and space of sedimentary successions is controlled by a complex interplay between physical, chemical and biological processes, which are nowadays difficult to construe from the geological record. Numerical models constitute a valuable tool to identify and quantify such controlling factors permitting a reliable 3D extrapolation and prediction of stratigraphic and facies architectures beyond outcropping rock strata. This study assesses the roles of three controlling parameters being carbonate production rate, relative sea-level changes and terrigenous clastic sediment supply, on the evolution of an Aptian carbonate system. The SIMSAFADIM-CLASTIC, a 3D process-based sedimentary-stratigraphic forward model, was used for this evaluation. The carbonate succession modelled crops out in the western Maestrat Basin (E Iberia), and corresponded to a platform-to-basin transition comprising three depositional environment-related facies assemblages: platform top, slope and basin. Testing of geological parameters in forward modelling results in a wide range of possible 3D geological scenarios. The documented distribution of facies and sequence-stratigraphic framework combined with a virtual outcrop model were used as a reference to perform geometric (quantitative) and architectural and stacking pattern (qualitative) research by model-data comparison. The time interval modelled spans 1450 ky. The best-fit simulation run characterizes and quantifies (1) relative sea-level fluctuations recording five different genetic types of deposit (systems tracts) belonging to two depositional sequences as expected from field-data analysis, (2) a rate of terrigenous clastic sediment input ranging between 0.5 and 2.5 gr/s, and (3) a mean autochthonous carbonate production maximum rate of 0.08 m/ky. Furthermore, the quantitative and qualitative sensitivity tests carried out highlight that the fluctuation of relative sea level exerted the main control on the resulting stratigraphic and facies architectures, whereas the effect of inflowing terrigenous clastic sediment is less pronounced. Facies assemblages show different sensitivities to each parameter, being the slope carbonates more sensitive than the platform top facies to inflowing fine terrigenous sediments. On slope depositional settings, siliciclastic input also controls stratal stacking patterns and the dimensions of the carbonate bodies formed. The final 3D model allows to spot architectural features such as stacking patterns that can be misinterpreted by looking at the resulting record in the outcrop or by using other 2D approaches, and facilitates the comprehension of reservoir connectivity highlighting the occurrence of initial disconnected regressive platforms, which were later connected during a transgressive stage.

Description: Highlights: • The pivot point for sea level shifted to the west of the Nino4 region in the 2000s. • This enabled the thermocline feedback to increase strongly in the Central Pacific. • The resulting increase in CP events maintains the pivot point to the west, a positive feedback mechanism. Monthly mean sea level variations computed using a linear, reduced-gravity, multi-mode model are combined with satellite measurements to explore why Central Pacific (CP) ENSO events occur more frequently since 2000s. The pivot point for sea level (and hence thermocline) variations has shifted westward in response to an increase in zonal wind stress variance in the western equatorial Pacific. As a result, the Nino4 region is increasingly to the east of the pivot point enabling the thermocline feedback to operate there, strengthening the Bjerknes feedback mechanism in the Nino4 region and leading to an increase in the occurrence of CP events. The increased variance of wind stress in the western Pacific is, in turn, caused by the resulting increase in the frequency of CP events. These arguments imply a positive feedback in which CP events are self-maintaining and suggest that they may be part of the natural variability of the climate system and could occur without the need for changes in external forcing.

Description: In situ pumps were used to collect size-fractionated particles (〉53 μm and 1–53 μm) from the upper ocean of the high latitude North Atlantic during spring and summer 2010, and samples were subsequently analysed for Al, P, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Cd, Ba and Pb. Two research cruises during May 2010 coincided with an eruption of the Eyjafjallajökull volcano in southern Iceland, which resulted in widespread dispersal of ash over the region. Ash deposition caused a noticeable perturbation of particulate trace element concentrations and content within marine particles in the Iceland Basin, relative to the Irminger Basin, most evident for lithogenic elements (Al, Ti, Fe), but also noticeable in elemental ratios for the other elements. The initial volcanic ash influence had largely disappeared by the third research cruise in July/August 2010, although there was evidence for a recent wind erosion event having transported remobilized volcanic ash from southern Iceland to the northern Iceland Basin in early July, further perturbing local trace element biogeochemistry. During summer 2010, concentrations of all measured elements except Ba were typically lower 10 m beneath the surface mixed layer relative to those within it, driven primarily by a rapid decrease in the concentrations of large (〉53 μm) biogenic particles. Depth-dependent trends were more variable over the next hundred metres for all elements except the biogenic elements P and Cd, for which concentrations decreased further. The continued loss of biogenic material with depth due to remineralization (reflected by particulate P concentrations) led to an increase in content per mass of material for all other elements measured. The observed differences in upper ocean particulate P and Fe distributions highlight the mechanism driving seasonal Fe limitation in the high latitude North Atlantic: rapid loss of P by remineralization regenerates dissolved phosphate close to the base of the mixed layer, while most particulate Fe persists deeper in the water column, removing the potential for resupply of dissolved Fe to surface waters.

Description: Highlights • In-situ temperature measurements were conducted at the Danube deep sea fan. • Operations were performed with the MARUM-MeBo200 seafloor drill rig. • The BSR is located ∼20 m below the current gas hydrate stability zone. • Seismic data suggest presence of shallower BSR-like events. Abstract Coring, geophysical logging, and in-situ temperature measurements were performed with the MARUM-MeBo200 seafloor rig to characterize gas hydrate occurrences in sediments of the Danube deep sea fan, off Romania, Black Sea. The new drilling data showed no evidence for significant gas hydrate saturations within the sediments but the presence of free gas at the depth of the bottom-simulating reflector (BSR). In-situ temperature and core-derived geochemical data suggest that the current base of the gas hydrate stability zone (BGHSZ) is ∼20 m shallower than the BSR. Investigation of the seismic data around the drill sites shows several locations where free gas previously trapped at a former BGHSZ migrated upwards forming a new reflection above the BSR. This shows that the gas hydrate system in the Danube deep sea fan is still responding to climate changes initiated at the end of the last glacial maximum.

Description: Body condition and energy reserves are important indicators of organism health, habitat suitability and predictors for the reproductive success in fish. In Greenland waters, Atlantic cod (Gadus morhua) inhabits different habitats in shallow and deep parts on top of the shelf and along slopes, where diet composition differs. We investigated the influence of habitat heterogeneity and trophic niche on body condition using organosomatic indicators, e.g. the morphometric index K, hepatosomatic and gonadosomatic indices, and biochemical indicators, e.g. lipid content and fatty acid compositions, of mature female cod. Body condition differed between sites and peaked in north-eastern regions in depths below 300 m towards the slope of the northern Irminger Sea. Trophic niches as indicated by stable isotope values and stomach composition data varied between sites, which was likely related to depth and differences between benthic and pelagic feeding regimes. Total lipid content and fatty acid profiles important for reproduction were associated with a pelagic diet comprised of mesopelagic fish and crustaceans. Interestingly, consumption of capelin was not linked to highest energy reserves as indicated by traditional body condition indices, such as K and the hepatosomatic index, but lowest ratios of eicosapentaenoic acid to arachidonic acid in gonads, which are known to be beneficial for high egg production. This shows that body condition on biochemical level can differ from conventionally used indices, which emphasizes the need to take fatty acid composition into account, when investigating condition and reproductive potential in cod. Our results emphasize that the factor habitat cannot be ignored for population replenishment of the cod stocks in Greenland waters and indicate that capelin as part of an Arcto-boreal diet benefits reproductive success in cod.

Description: Seagrass meadows are globally recognized as important coastal habitats due to the various ecological functions and ecosystem services they provide. Substantial global decline of seagrass habitats has been recorded over the last decades, underlining the need for extensive studies, including monitoring and mapping these habitats across their distributional range. Cymodocea nodosa (Ucria) Ascherson is the only seagrass species reported in the archipelago of Madeira (NE Atlantic) and systematic or reliable information of its occurrence is very scarce and mostly anecdotal. This study reports the discovery of a yearly-persistent patch of C. nodosa in the southeast coast of Madeira and provides insights into key ecological and biological aspects (e.g. density, leaf length, associated fauna and flora). Seasonal monitoring surveys over a 3-year period, indicate that (1) the patch has increased in size and shoot density over the study period, and (2) leaf lengths follow a typical seasonal pattern over the year. Accounts of past destruction of seagrass meadows in the island, underline the importance of continuous monitoring of the patch and adjacent areas to reveal how the current seagrass patch develops (i.e. patch continuity and/or disappearance), if it integrates a larger meadow and whether anthropogenic pressures as coastal development and/or associated terrigenous sediment runoff events will affect its resilience.

Description: Highlights • First dissolved Nd/Hf isotope and REE data from the Congo River Plume. • High REE and Hf fluxes from the Congo River to the southeast Atlantic. • Conservative river and surface seawater mixing of Nd/Hf isotopes and REEs/Hf at S 〉 23. • Congo River particles impact intermediate and deep water signals of NE Angola Basin. Abstract The Congo River is the second largest river by discharge in the world and a major source of element inputs into the South Atlantic Ocean. Yet, the element fluxes and transport mechanisms across and beyond its estuary and their impacts on the marine distribution and cycling of many major and trace elements are not well understood. We present the first combined dissolved neodymium (Nd) and hafnium (Hf) isotope and rare earth element (REE) concentration distributions following the Congo River plume along its flow path off the West African coast and along a connected offshore latitudinal section at 3°S. The Congo River freshwater itself is characterized by extraordinarily high Nd and Hf concentrations of up to 4000 pmol/kg and 54 pmol/kg, and by Nd (εNd) and Hf (εHf) isotope compositions that range between −15.6 and −16.4 and between 0.35 and −1.4, respectively. Our near- and offshore data indicate that at salinities above 23 conservative mixing of Congo-derived Nd and Hf concentrations and isotopic signatures with ambient surface seawater occurs for at least 1000 km to the northwest of the river mouth. This demonstrates a large spatial extent of the influence of the Congo plume on trace metal distributions in the eastern south Atlantic surface waters. A comparison between dissolved Nd and Hf fluxes from the Congo River and the shelf zone estimated based on radium isotope compositions indicate that release from Congo-derived particulate phases likely balances strong estuarine REE and Hf removal in the low salinity zone. The combined riverine and shelf zone flux for Nd is almost twice as high as that estimated for the Amazon River, despite that the Amazon discharge is about five times higher than that of the Congo River. Even the offshore Nd flux estimated for the 3 °S transect based on radium isotope compositions still corresponds to ∼40% of the Congo-shelf-zone flux and reaches 150 ± 50 Mg/year for Nd. Moreover, intermediate waters below the plume are strongly affected by exchange with particulate inputs from the Congo River given that Nd isotope signatures are inconsistent with values expected from large-scale water mass mixing and instead support unradiogenic Nd release either from sinking or deposited Congo-derived detrital material. Deep and bottom water isotopic signatures are also slightly affected by interaction with particles and benthic Nd release.

Description: We present porosity and free gas estimations and their uncertainties at anactive methane venting site in the UK sector of the North Sea. In the Scan-ner Pockmark area in about 150m water depth, we performed a multi-disciplinary experiment to investigate the physical properties of fluid flowstructures within unconsolidated glaciomarine sediments. Here we focus onthe towed controlled source electromagnetic (CSEM) data analysis with con-straints from seismic reflection and core logging data. Inferred backgroundresistivity values vary between 0.6–1 Ωm at the surface and 1.9–2.4 Ωm at150 mbsf. We calibrate Archie’s parameters with measurements on cores, andestimate porosities of about 50±10% at the seafloor decreasing to 25±3% at 150 mbsf which matches variations expected for mechanical compaction ofclay rich sediments. High reflectivity in seismic reflection data is consistentwith the existence of a gas pocket. A synthetic study of varying gas contentin this gas pocket shows that at least 33±8% of free gas are required to causea distinct CSEM data anomaly. Real data inversions with seismic constraintssupport the presence of up to 34±14% free gas in a 30–40 m thick gas pocketunderneath the pockmark within the stratigraphic highs of a till layer abovethe glacial unconformity in the Aberdeen Ground Formation.

Description: Highlights • Loess in Northern Iran sensitively reacted on Pleistocene climate change. • Dust accumulation and soil formation followed climate cycles of the Northern Hemisphere. • Pedostratigraphic correlation provides link within Southern Eurasian loess belt. • Southern Caspian Lowlands provide key area for climate reconstruction in West Asia. The southern Caspian Lowland sensitively reacted to Pleistocene climate change and is a key area for reconstructing climate dynamics and landscape evolution in Southern Eurasia. Loess-paleosol sequences (LPS) of the northern foothills of Alborz Mountains provide detailed records of climate-induced changes of dust accumulation and soil formation correlating with relatively dry or moist conditions of the past. The LPS at Neka-Abelou (NA) was studied in detail in order to understand these dynamics and provide a base for regional pedostratigraphic correlation. We have carried out high-resolution analyses of grain-size, sediment color, mass specific and frequency-dependent magnetic susceptibility and carbonate content and established a temporal framework as based on luminescence dating using a post-IR infrared stimulated luminescence (pIRIR) protocol and fading corrections. The LPS of NA is composed of finely textured loess, which is subdivided by at least eleven paleosols. Moreover, it contains a thin loess layer with lenses of trachytic tephra which most likely originated from the Damavand volcano and was deposited during Marine Isotope Stage (MIS) 4. The lower part of the LPS at NA consists of four strongly-developed reddish-brown paleosols (Bt, Btg horizons) separated by thin layers of pedogenically-altered loess indicating moist climate conditions and low dust accumulation rates during the Middle Pleistocene or earlier. The central part contains a pedocomplex of clay-rich paleosols composed of well developed Bt, ABk and Bw horizons formed under strongly reduced dust accumulation rates and intercalated by loess layers. Pedostratigraphic reasoning suggests that this pedocomplex formed during MIS 5, which is corroborated by luminescence dating. The pedocomplex reflects precession time scale climate change and represents an excellent pedostratigraphic marker recognized in numerous exposures along the northern foothills of the Alborz Mountains. The upper part of the LPS accumulated during the Last Pleniglacial and contains probably six weakly developed synsedimentary paleosols (CBk horizons) as well as the modern soil (Bt horizon). Magnetic susceptibility records show very close similarity with the pleniglacial sequence of the LPS at Toshan located about 100 km farther to the east of the Caspian Lowlands suggesting that the weak paleosols at both locations have formed synchronously, which is supported by luminescence dating. Their presence thus reflects at least a regional-scale climate change between dry phases and those of slightly increased edaphic moisture with ongoing dust supply. The LPS of the Caspian Lowlands document a multitude of changes between dominance of dust accumulation or pedogenesis controlled by moisture availability in the context of Pleistocene climate change. The proposed regional pedostratigraphy for the Late Quaternary provides a scheme for large-scale stratigraphic correlation and reconstruction of climate change in Southern Eurasia.

Description: Carbon capture and storage (CCS) is a key technology to reduce carbon dioxide (CO2) emissions from industrial processes in a feasible, substantial, and timely manner. For geological CO2 storage to be safe, reliable, and accepted by society, robust strategies for CO2 leakage detection, quantification and management are crucial. The STEMM-CCS (Strategies for Environmental Monitoring of Marine Carbon Capture and Storage) project aimed to provide techniques and understanding to enable and inform cost-effective monitoring of CCS sites in the marine environment. A controlled CO2 release experiment was carried out in the central North Sea, designed to mimic an unintended emission of CO2 from a subsurface CO2 storage site to the seafloor. A total of 675 kg of CO2 were released into the shallow sediments (~3 m 49 below seafloor), at flow rates between 6 and 143 kg/d. A combination of novel techniques, adapted versions of existing techniques, and well-proven standard techniques were used to detect, characterise and quantify gaseous and dissolved CO2 in the sediments and the overlying seawater. This paper provides an overview of this ambitious field experiment. We describe the preparatory work prior to the release experiment, the experimental layout and procedures, the methods tested, and summarise the main results and the lessons learnt.

Description: Carbon Capture and Storage (CCS) is a potential significant mitigation strategy to combat climate change and ocean acidification. The technology is well understood but its current implementation must be scaled up nearly by a hundredfold to become an effective tool that helps meet mitigation targets. Regulations require monitoring and verification at storage sites, and reliable monitoring strategies for detection and quantification of seepage of the stored carbon need to be developed. The Cseep method was developed for reliable determination of CO2 seepage signal in seawater by estimating and filtering out natural variations in dissolved inorganic carbon (C). In this work, we analysed data from the first-ever subsea CO2 release experiment performed in the north-western North Sea by the EU STEMM-CCS project. We successfully demonstrated the ability of the Cseep method to (i) predict natural C variations around the Goldeneye site over seasonal to interannual time scales; (ii) establish a process-based baseline C concentration with minimal variability; (iii) determine CO2 seepage detection threshold (DT) to reliably differentiate released- CO2 signal from natural variability and quantify released- CO2 dissolved in the sampled seawater. DT values were around 20 % of the natural C variations indicating high sensitivity of the method. Moreover, with the availability of DT value, the identification of released- CO2 required no preknowledge of seepage occurrence, but we used additional available information to assess the confidence of the results. Overall, the Cseep method features high sensitivity, automation suitability, and represents a powerful future monitoring tool both for large and confined marine areas.

Description: Marine sediments are an important source and sink of bio-essential trace metals to the ocean. However, the different mechanisms leading to trace metal release or burial are not fully understood and the associated fluxes are not well quantified. Here, we present sediment, pore water, sequential extraction and benthic flux data of Mn, Co, Ni, Cu, Zn and Cd along a latitudinal depth transect across the Peruvian oxygen minimum zone at 12°S. Sediments are depleted in Mn and Co compared to the lithogenic background. Diffusive Mn fluxes from the sediments into the bottom water (−26 to −550 μmol m−2 y−1) are largely consistent with the rate of Mn loss from the solid phase (−100 to −1160 μmol m−2 yr−1) suggesting that 50% or more of the sedimentary Mn depletion is attributed to benthic efflux. In contrast, benthic Co fluxes (~ −3 μmol m−2 yr−1) are lower than the rate of Co loss from the solid phase (up to −120 μmol m−2 yr−1), implying Co dissolution in the water column. The trace metals Ni, Cu, Zn and Cd are enriched within the sediments with respect to the lithogenic background. Uptake of Ni by phytoplankton in the photic zone and delivery with organic matter to the sediment surface can account for up to 100% of the excess Ni accumulation (87 to 180 μmol m−2 y−1) in shelf sediments near the coast, whereas at greater water depth additional scavenging by Mn- and Fe-oxides may contribute to Ni accumulation. Up to 20% of excess Cu (33 to 590 μmol m−2 y−1) and generally less than 20% of excess Zn (58 to 2170 μmol m−2 y−1) and Cd (6 to 260 μmol m−2 y−1) can be explained by delivery with fresh organic matter. Sequential extraction data suggest that the discrepancies between the known sources of Cd (and Cu) and their excess accumulation may be driven by the delivery of allochthonous sulphide minerals precipitated from the water column. Additionally, Cu may be scavenged by downward sinking organic material. In contrast, precipitation of Zn sulphide chiefly takes place in the sediment. Diffusive Zn fluxes into the sediment (21 to 1990 μmol m−2 y−1) match the excess Zn accumulation suggesting that Zn delivery is mediated by molecular diffusion from bottom waters. Considering the diverse behavioural pattern of trace metals observed in this study, we argue that declining oxygen and increasing hydrogen sulphide concentrations in a future ocean will modify trace metal fluxes at the seafloor and the trace metal stoichiometry of seawater.

Description: Highlights • Decoupling of volatile element enrichment and magmatic volatile influx. • Multiple sulfide generations with distinct trace element signatures. • Boiling-induced pyrite precipitation revealed by textures and Tl/Pb, Sb/Pb and Bi/Pb ratios. • Boiling-induced Au, electrum and Bi-telluride colloids lead to high Au grades. • Metals sources: shallow upflow- (60–80%) and deep reaction (20–40%) zone. Abstract Shallow (〈1500 mbsl) submarine arc-related hydrothermal systems can host base (Cu), precious (Au) and volatile elements (As, Se, Sb, Te, Tl) in significant quantities. Their wide application in the high-tech industry, but a potential eco-toxicological footprint gives them a strategic importance. However, the processes that concentrate these elements in submarine arc-related hydrothermal systems, compared to their mid-ocean ridge counterparts are still debated, and it is unclear whether boiling-related processes and/or the contribution of magmatic volatiles are key for their enrichment. We present bulk sulfide-sulfate, isotope (S and Pb), and high-resolution microanalytical data of hydrothermal sulfides from the Niua South fore-arc volcano in north Tonga, where numerous black-smoker type sulfide-sulfate chimneys emit boiling fluids with temperatures (up to 325 °C) near the seawater boiling curve at ~1170 m water depth. Hence, this system represents an ideal natural laboratory to investigate the effect of fluid boiling on base, precious, and volatile element enrichment associated with hydrothermal seafloor mineralization. At Niua South, textural and chemical variations of multiple pyrite (framboidal, euhedral and massive), chalcopyrite (linings), and sphalerite (dendrites and linings) generations are indicative for sulfide precipitation from early low-temperature (~240 °C) fluids that underwent abundant mixing with ambient seawater (low Se/Tl and Co/Ni ratios in pyrite) and from later high-temperature (up to 325 °C) (high Se/Tl and Co/Ni ratios in pyrite). In addition, crustiform inclusion-rich pyrite that precipitated from high-temperature boiling fluids shows low Bi/Pb, Tl/Pb and Sb/Pb ratios due to volatile element loss (e.g., Tl and Sb) to the vapor phase compared to pyrite that formed during the low temperature stage. By contrast, late sphalerite (~280 °C) is enriched in elements with an affinity to Cl-complexes like Mn, Co, Ni, Ga, Cd, In, and Sn, and therefore precipitated from the corresponding Cl-rich liquid phase. Gold occurs in solid-solution and as boiling-induced particles of native Au, electrum, and Au-rich Bi-tellurides in pyrite (up to 144 ppm Au), sphalerite (up to 60 ppm Au), and chalcopyrite (up to 37 ppm Au). These particles (〈5–10 µm) probably formed during fluid boiling causing an extreme Au enrichment (〉30 ppm) in the mature and late stage of chimney formation. Lead isotope data indicate that the hydrothermal fluids scavenged metals not only from the deeper basement in the reaction zone (20–40%), but also from young dacitic volcanic rocks near the seafloor in the upflow zone (60–80%). Sulfur isotope (δ34S = −0.3 to 4.4‰) and Se/S*106 values (〈1500) of hydrothermal sulfides provide no evidence for a magmatic volatile influx and indicate that S, and most metals and semi-metals were likely leached from the host rocks. Hence, volatile (As, Se, Sb, Te, Tl), and precious (Au) element enrichments in arc-related submarine hydrothermal systems can be decoupled from magmatic volatiles and are instead a result of boiling-induced trace element fractionation – a hydrothermal enrichment process, which has been underestimated to date.

Description: Highlights • Subduction initiation (SI) is a mechanism for forming Neotethyan ophiolites. • Ophiolites of Iran show SI exerts extensional stress on the overlying plate. • SI-related extension can affect broad regions of the overriding plate. Abstract Subduction initiation (SI) requires the sinking of one plate beneath another and this exerts extensional stress on the overlying plate. How broad a region is affected by SI-related extension is unclear because most of the clearest SI examples– such as Izu-Bonin-Mariana arc– are deep under the ocean. A major SI event is recorded in the Late Cretaceous forearc ophiolites of Iran, related to the subduction of Neotethyan oceanic lithosphere beneath Eurasia. This caused extreme extension of the Iranian plate, up to ~1000 km away from the proto-trench and generated a series of back-arc oceanic basins, sedimentary basins, and core complexes and exhumed high-P rocks. The Late Cretaceous Iran example shows that SI can cause strong extension over a much wider region of the overriding plate than heretofore imagined and offers an accessible natural laboratory for studying SI processes. This understanding also provides an attractive new explanation for the origin of the South Caspian Sea.

Description: Climate forcing is impacting polar marine ecosystems through increased variability of winter sea-ice dynamics, which likely influences the distribution, abundance and structure of zooplankton assemblages, and thereby trophodynamics of marine food webs. Due to the challenges of working in polar marine ecosystems, most knowledge on polar zooplankton community structure is derived from summer surveys. Here we examine the spatial distribution, abundance and community structure of macrozooplankton in relation to sea-ice and ocean-climate dynamics within the Antarctic Peninsula marine ecosystem over five consecutive winters. We compare the patterns revealed during winter with historical data collected in the same region during austral summer. Hydrographic and macrozooplankton data were collected from 〉100 standard stations off the northern Antarctic Peninsula during summer (2003–2011) and winter (2012–2016). Using multivariate methods, the environmental drivers and geographic structuring of the macrozooplankton community during winter and summer were investigated. Eight taxa made up 90% of total macrozooplankton abundance in winter including Metridia species, post-larval and larval Euphausia superba, post-larval Thysanoessa macrura, Limacina helicina, Chaetognatha, Ostracoda and Radiozoa. Eight slightly different taxa including Calanoides acutus, Salpa thompsoni, T. macrura (post-larvae and larvae), Metridia spp., E. superba larvae, Chaetognatha, and Rhincalanus spp. made up 87% of the total abundance in summer. Macrozooplankton clustered into five groups in winter and seven groups in summer. Winter macrozooplankton structure was more spatially consistent among years compared to summer regardless of sea-ice conditions. Salinity, chlorophyll a biomass, upper mixed layer depth and time of day were most strongly correlated with the multivariate ordination in winter whereas salinity, phaeopigment biomass and year had the highest correlations for summer, indicating the importance of similar physical features in both seasons. However, the importance of time scales differed among seasons. Although environmental determinants of summer and winter macrozooplankton community structure indicate that community structure and occurrence were strongly tied to regional variability of salinity and primary productivity gradients, macrozooplankton community structure is likely much more complex than only a few hydrographic variables can explain. Cluster boundaries are likely driven by dynamic locations of currents, fronts and localized eddies in any given season or year.

Description: Highlights • ~561 Ma old alkaline magmatism in the Damara Belt was caused by extensional tectonics. • Radiogenic isotopes constrain sources and AFC processes. • The alkaline rocks were generated by melting of enriched lithospheric mantle domains. • The lithospheric mantle was modified by ancient subduction zone processes. The 560.8 ± 2.4 Ma old Okamutambo Pluton is the easternmost intrusion of the syn-collisional Otjimbingwe Alkaline Complex (OAC; Damara Belt, Namibia) and consists of mafic to intermediate alkaline rocks that belong to the monzodiorite-syenite series. The studied samples are potassic (K2O/Na2O 〉 1) and have moderately high magnesium (MgO: 5.7–2.6 wt%), nickel (Ni: 66–26 ppm), and chromium (Cr: 223–62 ppm) concentrations. LILE (Ba: 2425–1243 ppm; Sr: 1359–941 ppm) and HFSE (Zr: 447–202 ppm, Nb: 32.8–16.4 ppm, Hf: 4.7–9.4 ppm, Ta: 1.2–2.0 ppm) contents are also high. Strontium and Nd isotope data reveal the existence of two magmatic suites indicating a multi-source origin. Group 1 monzonites-quartz monzonites have moderately evolved Sr and Nd isotopic compositions (initial 87Sr/86Sr: 0.7066 to 0.7073; initial εNd: −3.5 to −5.0) and radiogenic Pb isotope ratios (206Pb/204Pb: 17.65–18.02; 207Pb/204Pb: 15.62–15.67; 208Pb/204Pb: 38.19–38.32). In contrast, group 2 monzodiorites-syenites display more evolved Sr and Nd isotopic compositions (initial 87Sr/86Sr: 0.7088 to 0.7090; initial εNd: −6.7 to −7.1) but similar Pb isotope ratios (206Pb/204Pb: 17.63–17.82; 207Pb/204Pb: 15.64–15.66; 208Pb/204Pb: 38.21–38.37). Differentiation involved AFC processes in group 1 monzonites-quartz monzonites whereas group 2 monzodiorites-syenites were modified by fractional crystallization. Although second-order processes were operative, high total alkali contents, incompatible trace element concentrations in excess of bulk crustal values, and evolved isotopic compositions of the most primitive samples are source-controlled and provide insight into the origin of the parental magmas. With reference to experimental data from the literature, it is inferred that the Okamutambo alkaline rocks represent evolved melts that were generated through melting of enriched lithospheric mantle (phlogopite-lherzolite). The observed negative Nb-Ta and Ti anomalies and positive Pb anomalies in primitive mantle-normalized trace element patterns are in line with a mantle source that contains a recycled crustal component. Isotopic compositions indicate that mantle enrichment is an ancient feature that might be linked to Proterozoic subduction. At 561 Ma, the geodynamic regime in the Damara Orogen was mainly characterized by compression during convergence and continental collision between the Congo and Kalahari cratons which is difficult to reconcile with the generation of the OAC as alkaline magmatism is commonly associated with extensional tectonic regimes. The OAC is, however, associated with a major suture zone that may have been involved in localized transtensional tectonics during oblique flat subduction and thus enabled the generation and ascent of mantle-derived alkaline melts.

Description: Highlights • The crustal thickness of the Zhongsha Block ranging from ~6 to ~25 km. • Rapid transition from the Zhongsha Block to the adjacent oceanic basins was revealed. • Different oceanic structures were observed in the adjacent oceanic basins. • The pre-rift lithospheric configuration may affect the process of rifting and seafloor spreading. Abstract Continental rifting, break-up, and onset of seafloor spreading are inherently controlled by the segmentation and structure of the continental domain suffering from extension. Today, the Zhongsha Atoll (ZS) is wedged between the Northwest Sub-basin (NWSB) and the Southwest Sub-basin (SWSB), two oceanic abyssal basins of the South China Sea (SCS). The nature of the crust and the structure of the transition from continental to oceanic domain are key to revealing the processes and dynamics during the rifting and break-up of the Zhongsha block. In this paper, we present a P-wave velocity model obtained from both forward modeling and tomographic inversion of wide-angle seismic line OBS2017-2. The results support the continental nature of the Zhongsha Block with a thickness of up to ~25 km. However, the transition from the thick continental domain of the ZS into both adjacent abyssal basins shows clear differences. To the north, a ~120 km wide domain of extended continental crust was observed. Farther north, the NWSB is characterized as a narrow basin with typical oceanic crust. The transitional domain between the continental and oceanic crust shows a ~30–40 km wide region with a high-velocity lower crust reflecting excessive magmatism. In contrast, the SWSB is characterized by a sharp transition from the thick continental crust of the ZS to thin oceanic crust which is probably underlain by serpentinized mantle. The strong rheological properties of the pre-rift crust in the western part of the SCS margin may be the reason that rifting concentrated on narrow rifts and thinning focused on necking domains, while the ZS avoided any intense extension. The configuration of rigid blocks thereafter affected the break-up position and the style of oceanic crust.

Description: Gas hydrates have gained increasing attention in energy and environmental fields and have potential applications in gas storage and transport, carbon dioxide sequestration, and flow assurance. Nevertheless, the kinetics of hydrate formation are still not well understood. In situ high-resolution X-ray computed tomography measurements were performed to monitor xenon hydrate formation on water droplets and ice spheres. For the first time, three-dimensional thickness meshes were used to quantify and visualize the kinetics of hydrate formation. The evolution of the hydrate morphology was investigated, and the time-dependent kinetic parameters were obtained, including the hydrate shell thickness and inner and outer diameters and the effective volume fraction of hydrate particles. The results indicate that the formation of gas hydrates undergoes an initial reaction-controlled stage followed by a mass-transfer-limited growth stage. For hydrate formation from a water droplet with an initial diameter of 1.66 mm, the hydrate shell thickness was approximately 30 μm and the effective volume fraction of hydrate particles was approximately 11% at 12 h after hydrate formation began. The standard deviation of the shell thickness, which indicates the surface roughness of the hydrate shell, increased with time for hydrate formation from water droplets. The results presented in this study renew our knowledge on the kinetics of hydrate formation, which is essential for their use in flow assurance and other hydrate-related technologies.

Description: Highlights • Regardless of eruptive style, Masaya magmas are compositionally similar. • Volatile contents are higher in Plinian samples, but low compared to CAVA magmas. • All Masaya magmas undergo extensive pre-eruptive degassing at low pressure. • Initial volatiles are higher than observed, but do not control eruptive style. • The state of the volcano's conduit modulates eruptive style in a top–down manner. Abstract Highly explosive Plinian eruptions of basaltic magma are enigmatic because low melt viscosities should inhibit such eruptive style. Masaya volcano, Nicaragua, is a persistently active basaltic system capable of a wide range of eruptive styles, from open-conduit lava lake activity to voluminous Plinian eruptions; it is thus an ideal natural laboratory to constrain potential controls on basaltic eruption style. Here we report the major, trace, and volatile (CO2, H2O, S, Cl, F) element composition of olivine-, plagioclase- and clinopyroxene-hosted melt inclusions as well as matrix glasses from lava lake ejecta and two Plinian tephra deposits—the 2.1 ka Masaya Triple Layer and the 1.8 ka Ticuantepe Lapilli—to test whether pre-eruptive volatile contents and degassing history may be linked to eruptive style. All samples display a relatively narrow and largely overlapping basaltic–basaltic andesitic compositional range ( wt.% SiO2, wt.% MgO) with similar trace element signatures (e.g., , ). However, lava lake and Plinian samples show systematic differences in pre-eruptive volatile contents, forming distinct groups with mean H2O contents of wt.% (lava lake), wt.% (Masaya Triple Layer), and wt.% (Ticuantepe Lapilli). Together, these groups generate broad positive correlations between S, Cl and H2O concentrations, with maximum values reaching 920 ppm, 1300 ppm and 2.3 wt.%, respectively, which are low compared to typical Central American arc magmas. Magma temperature estimates overlap and average at 30°C, while volatile saturation pressures are low, mainly 〈100 MPa, although only lava lake samples record pressures 〈31 MPa. These observations reiterate the compositionally buffered state of the volcano's magmatic system highlighted by previous work and demonstrate that — regardless of eruption style — all Masaya magmas undergo variable, but extensive, pre-eruptive degassing at low pressure. Geohygrometry, gas emissions, and H2O/Ce–Ba/La systematics suggest initial, undegassed H2O contents on the order of 3.9–5.5 wt.%. Our results imply that pre-eruptive volatile contents are not the culprit for Plinian events at Masaya. Instead, we propose that the volcano's vigorous magma supply is modulated in a top–down manner to produce a wide range of eruptive styles, whereby temporary sealing of the conduit may instigate a transition to explosive behavior. In this model, rapid magma ascent is triggered when the seal eventually breaks from degassing-induced pressurization, yielding high degrees of undercooling, rapid microlite growth, and a dramatic increase in magma viscosity and explosive eruption potential. There may thus be a thin line between open-conduit conditions and Plinian eruptions at Masaya.

Description: Highlights • Unprecedented dense coverage of ocean-bottom seismometer data reveals seismic velocity variations within a vertical fluid pathway. • There are zones of both positive (faster) and negative (slower) velocity within the fluid pathway compared to the background formation velocities. • Velocity reductions are related to free gas in the fluid pathway, while the reason for velocity increases is unclear but potentially caused by cementation. Abstract Subsurface CO2 storage is a key strategy to reduce greenhouse gas emission, but leakage of CO2 along natural fluid pathways may affect storage formation integrity. However, the internal structure and the physical properties of these focused fluid conduits are poorly understood. Here, we present a three-dimensional seismic velocity model of an active fluid conduit beneath the Scanner Pockmark in the Central North Sea, derived from ocean-bottom seismometer data. We show that the conduit, which manifests as a pipe structure in seismic data, is separated into two parts. The upper part, extending to 260 m depth, i.e. 110 m below the seafloor, is characterised by seismic velocities up to 100 m/s slower than the surrounding strata. The deeper part is characterized by a 50 m/s seismic velocity increase compared to background velocity. We suggest that the upper part of the pipe structure represents a network of open fractures, partly filled with free gas, while the reason for the velocity increase in the lower part remains speculative. These observations suggest that active pipes can be internally heterogeneous with some intervals probably being open fluid pathways and other intervals being closed. This study highlights the complexity in evaluating focused fluid conduits and the necessity of their detailed assessment when selecting CO2 storage sites.

Description: Highlights: • Effects of widespread NIS on ecosystem features and properties were quantified. • Most impactful NIS, processes underlying the changes and sources of uncertainty were identified. • Among communities, fish have been impacted the most while the pelagic realm is more affected than the benthic. • Significant effects were evident on the entire food web. • The effect size method offers a robust approach for general applications on quantification of the effects of NIS. Abstract: The introduction of non-indigenous species (NIS) is a major driver for global change in species biogeography, often associated with significant consequences for recipient ecosystems and services they provide for humans. Despite mandated by several high-level international legislative instruments, comprehensive quantitative evaluation on ecosystem impacts of marine NIS is scarce and lack a robust and data-driven assessment framework. The current study is aiming at fulfilling this gap, through quantitative assessment on the effects of the widespread NIS of the Baltic Sea on multiple ecosystem features and components including direct food-web effects. The outcomes of this study allowed identifying the most impacting widespread NIS, together with defining the processes underlying the most significant changes and outlined major sources of uncertainty. Lack and/or bias in the availability of evidence of impacts was recorded for several (both recent and early) introductions. Realizing a sophisticated, data and information-hungry framework for the evaluation of ecosystem impacts of NIS is not pragmatic for management purposes in the foreseeable future. Instead, simple approaches, such as application of common statistical parameters like absolute effect size, are more likely to result in tangible outcomes. As bearing no unit, effect sizes can be later easily aggregated across taxa, affected ecosystem features or spatial scales. The proposed approach enables performing systematic comparisons on the severity of impacts of different NIS along different study disciplines and ecosystems.

Description: Fluid-escape structures within sedimentary basins permit pressure-driven focused fluid flow through inter-connected faults, fractures and sediment. Seismically-imaged chimneys are recognised as fluid migration pathways which cross-cut overburden stratigraphy, hydraulically connecting deeper strata with the seafloor. However, the geological processes in the sedimentary overburden which control the mechanisms of genesis and temporal evolution require improved understanding. We integrate high resolution 2D and 3D seismic reflection data with sediment core data to characterise a natural, active site of seafloor methane venting in the UK North Sea and Witch Ground Basin, the Scanner pockmark complex. A regional assessment of shallow gas distribution presents direct evidence of active and palaeo-fluid migration pathways which terminate at the seabed pockmarks. We show that these pockmarks are fed from a methane gas reservoir located at 70 metres below the seafloor. We find that the shallow reservoir is a glacial outwash fan, that is laterally sealed by glacial tunnel valleys. Overpressure generation leading to chimney and pockmark genesis is directly controlled by the shallow geological and glaciogenic setting. Once formed, pockmarks act as drainage cells for the underlying gas accumulations. Fluid flow occurs through gas chimneys, comprised of a sub-vertical gas-filled fracture zone. Our findings provide an improved understanding of focused fluid flow and pockmark formation within the sediment overburden, which can be applied to subsurface geohazard assessment and geological storage of CO2.

Description: Elevated organic matter (OM) export flux promotes marine anoxia, thus increasing carbon sequestration efficiency and decreasing atmospheric carbon dioxide levels. However, the mechanisms that trigger and sustain anoxic events-particularly those associated with nutrient-poor, oligotrophic surface waters-remain poorly constrained. Mediterranean Sea sapropels are well-preserved sediments deposited during episodic anoxic events throughout the Plio-Pleistocene; as such, they may provide unique insight into the biogeochemical and ecological drivers of-and responses to-marine anoxia. Using biomarker distributions, we demonstrate that anaerobic ammonium oxidizing (anammox) bacteria and diazotrophic endosymbionts of mat- and/or raft-forming diatoms were both abundant during sapropel events, particularly in the Ionian and Libyan seas. In these sapropels, the carbon isotope compositions of anammox biomarkers directly capture progressive C-13-depletion in deep-water dissolved inorganic carbon, indicating sustained carbon sequestration. To explain these observations, we propose a reinforcing feedback whereby initial nutrient and/or circulation perturbations promote fixed nitrogen loss via intensified anammox and heterotrophic denitrification, which in turn favors proliferation of rapidly sinking diatom-diazotroph symbiotic consortia, increases OM burial flux, and sustains anoxia. This mechanism resolves the long-standing conundrum that small and buoyant diazotrophs are apparently associated with high OM export during periods of marine anoxia and oligotrophy.

Description: Highlights: • Sea urchin food consumption and gonad index followed thermal performance curves. • Body size and sex interacted with temperature and influenced food consumption rates. • Only body size, not sex, in addition to temperature influenced gonad indices. • Larger sea urchins were impacted to a greater extent by warmer temperatures. Rising sea surface temperatures affect the feeding behaviour and reproductive success of many coastal benthic invertebrates. This experimental study investigated the effects of ocean warming on macroalgal food consumption rates in the sea urchins Arbacia lixula and Paracentrotus lividus from Madeira Island to assess how the feeding pressure they exert may change under warmer ocean conditions. Additionally, in A. lixula, the relationship between temperature and the gonad index was examined to estimate potential future reproductive output. Over the course of 25 days, 180 individuals of each species were exposed to temperatures between 22 degrees C and 31 degrees C. After 20 days, consumption rates were assessed in 48-h feeding trials. Gonad indices of A. lixula were determined on the last day of the experiment. In the thermal range investigated, both traits were found to be unimodal functions of temperature. In addition to temperature, consumption rates in both species and the gonad indices in A. lixula were influenced by body size, while feeding in A. lixula also varied between sexes. Maximum food consumption rates (A. lixula and P. lividus) as well as maximum gonad indices (only A. lixula) were observed between 25 degrees C and 26 degrees C. These values are at the upper end of the temperature range that currently prevails around Madeira, and may become average summer temperatures by the year 2100. Consequently, both sea urchin species may thrive during future warm summers and may enhance their top-down control on local macroalgal populations.

Description: Highlights: • Unique 30-years data of currents and temperature below 1000 m in the Madeira Basin. • Inter-decadal and long term changes were examined between 1000 m and the bottom. • Temperature increase by 0.03 ± 0.01 °C/year (1000 m) and 0.02 ± 0.02 °C/year at 1600 m. • No significant changes at 3000 m and 5000 m at long-term scale. • The currents and kinetic energy increased in the entire water column over 30-years. Abstract: Data from the deep-sea mooring Kiel 276 (33 N, 22W), 5300 m water depth in the northeast Atlantic, was used to investigate the temporal variability of temperature and currents below the main thermocline (1000 m, 1600 m, 3000 m, 5000 m) in the 30-year period (between 1980 and 2009). Daily averages were the basis to assess the temperature and currents changes, as well as kinetic energy, from annual to decadal and long-term scales. Below the main thermocline, no seasonal signal was identified for both, temperature and currents, during the 30 years. The record-length linear temperature trends at 1000 m and 1600 m are 0.03 ± 0.01 °C year−1 and 0.02 ± 0.02 °C year−1, respectively. The mean currents also intensified within the decades in the entire water column, and as a consequence, the mean kinetic energy increased. The fluctuating kinetic energy increased on a decadal scale only at 1000 m, as a possible consequence of the increase in the strength of Mediterranean Water lenses (MEDDIES) that crossed the mooring site. During the period 2001–2009, six MEDDIES crossed the Kiel 276 site, in addition to the 10 MEDDIES identified earlier during the previous 20 years, between 1980 and 2000 (Siedler et al., 2005). The integral time scales are of the same order in all depths (between 30 to 40 days), indicating that events occur on similar time scales, with mesoscale signals dominating and being present within the entire water column.

Description: Dissolved lignin phenols, chromophoric dissolved organic matter (DOM), and in situ fluorescence were determined in waters of the Laptev Sea and major Arctic basins, and they were compared with dissolved iron (dFe) distributions to elucidate the sources, molecular characteristics and distributions of iron-binding ligands in the Arctic Ocean. In the Transpolar Drift region (TPD), concentrations of dFe were positively correlated with concentrations of lignin phenols and multiple optical proxies of DOM composition and source. Strong relationships between dFe and visible and ultraviolet wavelength fluorescent DOM indicated that vascular plant and algal-derived DOM contributed to the dFe-ligand pool. These observations are consistent with previous studies suggesting the association of dFe with humic terrigenous and marine organic ligands. The primary sources of iron-binding ligands appear to be the riverine discharge of terrigenous DOM, marine organic matter produced on the shelves, and degradation products of plankton-derived organic matter in the shelf sediments. A stronger relationship between dFe and visible wavelength CDOM fluorescence than with lignin phenols suggested the presence of multiple terrigenous ligands, such as aromatic tannins. The aromatic nature of these terrigenous ligands was indicated by a strong relationship between dFe and the absorption coefficient at 254 nm. A strong negative correlation between the p-hydroxyl to vanillyl lignin phenols ratio and dissolved iron concentrations indicated recently-discharged terrigenous DOM (tDOM) was an important source of iron-binding ligands. Given the strong relationships of marine and terrigenous DOM with dissolved iron, iron-binding functional groups appear to occur in diverse molecules of multiple sources. Examples of such iron-binding functional groups included catechols and carboxylates found in lignins and tannins of terrigenous origins and carboxyl-rich alicyclic molecules (CRAM) of terrigenous and marine origins. The observed dFe distributions in the Arctic Ocean could not be explained by the presence of a single ligand type, but rather by a potpourri of ligand molecules of varying concentrations and binding strengths. This molecular diversity of ligands and associated binding strengths ultimately controls the distribution and transport of dFe in the Arctic Ocean and beyond.

Description: Highlights ● We developed a pH eddy covariance system to detect a sub-seafloor CO2 release. ● It detected CO2 emission to the water column at injection rates of 5.7–143 kg d − 1. ● It was also sensitive enough to quantify benthic biological CO2 production. ● Close to bubble streams, the kinetics of aqueous CO2 equilibration are important. ● This system can be used to detect, attribute, and quantify seafloor sources of CO2. We detected a controlled release of CO2 (g) with pH eddy covariance. We quantified CO2 emission using measurements of water velocity and pH in the plume of aqueous CO2 generated by the bubble streams, and using model predictions of vertical CO2 dissolution and its dispersion downstream. CO2 (g) was injected 3 m below the floor of the North Sea at rates of 5.7–143 kg d − 1. Instruments were 2.6 m from the center of the bubble streams. In the absence of injected CO2, pH eddy covariance quantified the proton flux due to naturally-occurring benthic organic matter mineralization (equivalent to a dissolved inorganic carbon flux of 7.6 ± 3.3 mmol m − 2 d − 1, s.e., n = 33). At the lowest injection rate, the proton flux due to CO2 dissolution was 20-fold greater than this. To accurately quantify emission, the kinetics of the carbonate system had to be accounted for. At the peak injection rate, 73 ± 13% (s.d.) of the injected CO2 was emitted, but when kinetics were neglected, the calculated CO2 emission was one-fifth of this. Our results demonstrate that geochemical techniques can detect and quantify very small seafloor sources of CO2 and attribute them to natural or abiotic origins.

Description: Earth's mantle is more than 2800 km deep, compositionally heterogenous, and potentially stratified. However, understanding of its heterogeneities and stratification is limited. Recently, plume-like anomalies were detected to exhibit different types of anomalous behavior at ∼1000 km depth, where they laterally pond, neck or broadly penetrate to the upper mantle, suggesting that their behavior may be influenced by possible viscosity or density stratification near this depth. However, the specific key reasons are unclear. Here, we use 2D thermal-mechanical-chemical modeling to constrain the key factors causing these large-scale plume-related anomalies. Upward mantle plume penetration at ∼1000 km depth is mainly caused by large source volume and excess temperature, whereas its necking and lateral extension at this depth can only be caused by viscosity and composition-related density stratification, respectively. Considering the various plume behaviors at this proposed boundary, we show that Earth's mantle is likely heterogeneously stratified at ∼1000 km depth, with regional viscosity and/or density changes of different lateral scales and vertical gradients. We speculate that this boundary separates the upper depleted mantle from the primordial mantle domain below. This fundamental boundary has been progressively evolving during stratification of Earth's mantle through melt extraction and mantle stirring throughout Earth history. Highlights • Different plume behaviors suggest regional mantle layering at ∼1000 km depth. • The viscosity layering can lead to plume necking at ∼1000 km depth without ponding. • A composition-induced density stratification can explain the ponding phenomenon. • The regional mantle layering is related to density and/or viscosity stratification. • This likely indicate the boundary between depleted mantle and primordial mantle.

Description: Highlights • All known observations for Area of Particular Environmental Interest 6 presented. • Assess morphology, sediments, nodules, oceanography, biogeochemistry and ecology. • APEI-6 partially representative of nearby exploration areas yet clear differences. • Present scientific synthesis and management implications for Clarion Clipperton Zone. To protect the range of habitats, species, and ecosystem functions in the Clarion Clipperton Zone (CCZ), a region of interest for deep-sea polymetallic nodule mining in the Pacific, nine Areas of Particular Environmental Interest (APEIs) have been designated by the International Seabed Authority (ISA). The APEIs are remote, rarely visited and poorly understood. Here we present and synthesise all available observations made at APEI-6, the most north eastern APEI in the network, and assess its representativity of mining contract areas in the eastern CCZ. The two studied regions of APEI-6 have a variable morphology, typical of the CCZ, with hills, plains and occasional seamounts. The seafloor is predominantly covered by fine-grained sediments, and includes small but abundant polymetallic nodules, as well as exposed bedrock. The oceanographic parameters investigated appear broadly similar across the region although some differences in deep-water mass separation were evident between APEI-6 and some contract areas. Sediment biogeochemistry is broadly similar across the area in the parameters investigated, except for oxygen penetration depth, which reached 〉2 m at the study sites within APEI-6, deeper than that found at UK1 and GSR contract areas. The ecology of study sites in APEI-6 differs from that reported from UK1 and TOML-D contract areas, with differences in community composition of microbes, macrofauna, xenophyophores and metazoan megafauna. Some species were shared between areas although connectivity appears limited. We show that, from the available information, APEI-6 is partially representative of the exploration areas to the south yet is distinctly different in several key characteristics. As a result, additional APEIs may be warranted and caution may need to be taken in relying on the APEI network alone for conservation, with other management activities required to help mitigate the impacts of mining in the CCZ.

Description: Highlights • Cu speciation was investigated for the first time in the South-East Atlantic using CLE-AdCSV. • [Cu2+] were mostly below the putative biolimiting threshold of various marine microorganisms. • Cu speciation parameters showed a poor correlation with assessed biogeochemical parameters. • Spatial differences in Cu speciation parameters suggest that biogeochemical processes and sources strongly influence Cu speciation. Organic ligands play a key role in the marine biogeochemical cycle of copper (Cu), a bio-essential element, regulating its solubility and bioavailability. However, the sources, abundance, and distribution of these ligands are still poorly understood. In this study, we examined vertical Cu speciation profiles from the South-East Atlantic (GEOTRACES section GA08). Profiles were collected from a range of ocean conditions, including the Benguela upwelling region, the oligotrophic South Atlantic Gyre, and the Congo River outflow. In general, the lack of a significant correlation between most of the parameters assessed here with Cu speciation data obscures the provenance of Cu-binding ligands, suggesting that Cu speciation in the South-East Atlantic is influenced by a complex interplay between biotic and abiotic processes. Nevertheless, the total dissolved Cu (CuT) illustrated an allochthonous origin in the working area, while Cu-binding ligands showed both an allochthonous and a biogenic, autochthonous origin. Pigment concentrations showed that the phylogeography of different microorganisms influenced the spatial features of the Cu-binding ligand pool in the South-East Atlantic. Allochthonous Cu-binding ligand sources in the upper water column are likely associated with dissolved organic matter which originated from the Congo River and the Benguela upwelling system. Deep water ligand sources could include refractory dissolved organic carbon (DOC), resuspended benthic inputs, and lateral advected inputs from the shelf margin. The degradation of L1-type ligands and/or siderophores in low oxygen conditions may also be a source of L2-type ligands in the deep. Free Cu ion levels (1.7 to 156 fM), the biologically available form of CuT, were below the putative biolimiting threshold of many marine organisms. Two classes of ligands were found in this study with total ligand concentrations ([LT]) ranging from 2.5 to 283.0 nM and conditional stability constants (logKCuL, Cu2+cond) ranging from 10.7 to 14.6. The Cu speciation values were spatially variable across the three subregions, suggesting that biogeochemical processes and sources strongly influence Cu speciation. Highlights • Cu speciation was investigated for the first time in the South-East Atlantic using CLE-AdCSV. • [Cu2+] were mostly below the putative biolimiting threshold of various marine microorganisms. • Cu speciation parameters showed a poor correlation with assessed biogeochemical parameters. • Spatial differences in Cu speciation parameters suggest that biogeochemical processes and sources strongly influence Cu speciation.

Description: Manganese nodules are a potential source of critical metals such as Cu, Ni, and Co and are widely distributed on the abyssal plains of the global oceans. A polymetallic nodule metallogenic belt with a heterogeneous and spatially clustered nodule distribution was recently discovered in NW Pacific inter-seamount basin (NPIB) areas. However, the geological processes that regulate the nodule occurrence in that region are unresolved. Here, we report on the characteristics of a high-density field of manganese nodules in the abyssal plain north of Suda Seamount. Ship-borne multibeam bathymetric data reveal a typical seamount sector-collapse topography characterized by radial lineaments of debris channels and ridges formed by rapid debris-avalanche flow. Backscatter data linked with underwater observation indicate that manganese nodules are more concentrated (50%–80% areal coverage) along the main body of the debris apron compared to adjacent neighboring areas (〈30%). The extremely high concentrations (~80% areal coverage) characterized by overlapping nodules are apparently associated with downslope movement, possibly triggered by block movement along the fault slip plane or by gravity processes. Our results indicate that seamount sector collapse may have provided sufficient nucleus material for nodule growth and contributed to high nodule concentrations locally. The destruction of submarine volcanic edifices is universal, and the debris aprons and plains around such seamounts are potential prospecting areas for manganese nodule resources throughout the NPIB.

Description: Rivers are an important transport route of anthropogenic litter from inland sources toward the sea. A collaborative (i.e. citizen science) approach was used to evaluate the litter pollution of rivers in Germany: schoolchildren within the project “Plastic Pirates” investigated rivers across the entire country during the years 2016 and 2017 by surveying floating macrolitter at 282 sites and taking 164 meso−/microplastic samples (i.e. particles 24.99–5 mm, and 4.99–1 mm, respectively). Floating macrolitter was sighted at 54% of sampling sites and floating macrolitter quantities ranged from 0 to 8.25 items m−1 h−1 (average of 0.34 ± 0.89 litter items m−1 h−1). Floating meso−/microplastics were present at 57% of the sampling sites, and floating meso−/microplastic quantities ranged from 0 to 220 particles h−1 (average of 6.86 ± 24.11 items h−1). As only particles 〉1 mm were sampled and analyzed, the pollution of rivers in Germany by microplastics could be a much more prevalent problem, regardless of the size of the river. We identified six plastic pollution hotspots where 60% of all meso−/microplastics collected in the present study were found. These hotspots were located close to a plastic-producing industry site, a wastewater treatment plant, at and below weirs, or in residential areas. The composition of the particles at these hotspots indicates plastic producers and possibly the construction industry and wastewater treatment plants as point sources. An identification of litter hotspots would enable specific mitigation measures, adjusted to the respective source, and thereby could prevent the release of large quantities of small plastic particles in rivers. The adopted large-scale citizen science approach was especially suitable to detect pollution hotspots by sampling a variety of rivers, large and small, and enabled a national overview of litter pollution in German rivers.

Description: Highlights: • Characterization of enzymes from bone-degrading marine microbiomes. • Enzymes degrade sialo/glyco-proteins at multiple conditions of pH and temperatures. • Enzyme cocktails are useful for valorising bone residues in biorefinery industry. Abstract: Many microorganisms feed on the tissue and recalcitrant bone materials from dead animals, however little is known about the collaborative effort and characteristics of their enzymes. In this study, microbial metagenomes from symbionts of the marine bone-dwelling worm Osedax mucofloris, and from microbial biofilms growing on experimentally deployed bone surfaces were screened for specialized bone-degrading enzymes. A total of 2,043 taxonomically (closest match within 40 phyla) and functionally (1 proteolytic and 9 glycohydrolytic activities) diverse and non-redundant sequences (median pairwise identity of 23.6%) encoding such enzymes were retrieved. The taxonomic assignation and the median identity of 72.2% to homologous proteins reflect microbial and functional novelty associated to a specialized bone-degrading marine community. Binning suggests that only one generalist hosting all ten targeted activities, working in synergy with multiple specialists hosting a few or individual activities. Collagenases were the most abundant enzyme class, representing 48% of the total hits. A total of 47 diverse enzymes, representing 8 hydrolytic activities, were produced in Escherichia coli, whereof 13 were soluble and active. The biochemical analyses revealed a wide range of optimal pH (4.0–7.0), optimal temperature (5–65 °C), and of accepted substrates, specific to each microbial enzyme. This versatility may contribute to a high environmental plasticity of bone-degrading marine consortia that can be confronted to diverse habitats and bone materials. Through bone-meal degradation tests, we further demonstrated that some of these enzymes, particularly those from Flavobacteriaceae and Marinifilaceae, may be an asset for development of new value chains in the biorefinery industry.

Description: Highlights • Hydrography and convection reconstructed in the Nordic Seas during MIS 11. • Active convection in the Nordic Seas occurred during prolonged freshwater input. • Freshwater input does not always impede convection on interglacial timescales. • Onset of polar convection may have helped to sustain interglacial conditions. Abstract The Atlantic meridional overturning circulation (AMOC) is a critical element of Earth's climate system and it is currently weakening. While this weakening is frequently explained by freshwater-driven disruptions to deep-water formation, uncertainties about the impacts of prolonged freshening limit our capacity to predict its future state. For example, during the warm and unusually long marine isotope stage (MIS) 11 interglacial, ∼424 to 374 ka, several lines of evidence suggest that a strong AMOC persisted concomitant with fresher-than-present conditions in the Nordic Seas, challenging our current understanding of deep-water formation. Here, we present new foraminifer-bound nitrogen isotope data along with multiple additional geochemical reconstructions of upper-ocean hydrography in the Nordic Seas during this anomalous interval. Our data suggest that a weak summer stratification was driven by the prolonged upper-ocean accumulation of freshwater beginning at the onset of the climatic optimum, ∼410 to 407 ka, which could have helped precondition the region for deep-water formation. A box model constrained by paleo-proxy data additionally suggests that the density gradient between the subpolar North Atlantic and Nordic Seas was favorable for the onset of deep-water formation in the Nordic Seas during the climatic optimum. It is thus likely that the Nordic Seas became a locus of deep-water formation around this time. Enhanced northern-hemisphere heating driven by deep-water formation in the Nordic Seas may have been important for delaying glacial conditions, thereby driving the extended warming characteristic of MIS 11. Such findings may also be relevant for near-future changes under a relatively fresher high-latitude North Atlantic.

Description: Highlights • Rayleigh-wave phase velocity in the wider Dinarides region using the two-station method. • Uppermost mantle shear-wave velocity model of the Dinarides-Adriatic Sea region. • Velocity model reveals a robust high-velocity anomaly present under the whole Dinarides. • High-velocity anomaly reaches depth of 160 km in the northern Dinarides to more than 200 km under southern Dinarides. • New structural model incorporating delamination as one of the processes controlling the continental collision in the Dinarides. The interaction between the Adriatic microplate (Adria) and Eurasia is the main driving factor in the central Mediterranean tectonics. Their interplay has shaped the geodynamics of the whole region and formed several mountain belts including Alps, Dinarides and Apennines. Among these, Dinarides are the least investigated and little is known about the underlying geodynamic processes. There are numerous open questions about the current state of interaction between Adria and Eurasia under the Dinaric domain. One of the most interesting is the nature of lithospheric underthrusting of Adriatic plate, e.g. length of the slab or varying slab disposition along the orogen. Previous investigations have found a low-velocity zone in the uppermost mantle under the northern-central Dinarides which was interpreted as a slab gap. Conversely, several newer studies have indicated the presence of the continuous slab under the Dinarides with no trace of the low velocity zone. Thus, to investigate the Dinaric mantle structure further, we use regional-to-teleseismic surface-wave records from 98 seismic stations in the wider Dinarides region to create a 3D shear-wave velocity model. More precisely, a two-station method is used to extract Rayleigh-wave phase velocity while tomography and 1D inversion of the phase velocity are employed to map the depth dependent shear-wave velocity. Resulting velocity model reveals a robust high-velocity anomaly present under the whole Dinarides, reaching the depths of 160 km in the north to more than 200 km under southern Dinarides. These results do not agree with most of the previous investigations and show continuous underthrusting of the Adriatic lithosphere under Europe along the whole Dinaric region. The geometry of the down-going slab varies from the deeper slab in the north and south to the shallower underthrusting in the center. On-top of both north and south slabs there is a low-velocity wedge indicating lithospheric delamination which could explain the 200 km deep high-velocity body existing under the southern Dinarides.

Description: Seismic interpretation of mobile shales is challenging, mostly because of their unclear seismic expression. Imaging of mobile shales is difficult because of their low seismic-impedance contrast with many sedimentary rocks, spatial variation of their seismic properties, complex geometries of mobile-shales structures, and their complex internal structures. Furthermore, their seismic properties depend strongly on both overpressure and fluid content, which are difficult to predict. To unravel this problem, we reviewed the physical properties of shales, merging data from in situ determinations of density and sonic velocities with experimental data and modeling results. We analyzed how diagenetic transformations during shale burial modify their physical properties and seismic characteristics. We reviewed conditions for smectite-illite transformation and gas generation (mostly methane) by oil cracking to evaluate how thermal gradient, shale composition, and hydrocarbon content modify the densities, sonic velocities, and seismic expressions of mobile shales. We then incorporated the amount and type of fluids released in shales during diagenesis into a study of seismic reflectivity of mobile shales. Results derived theoretically for various types of mobile-shale contacts are compared with high-quality seismic examples, including mud volcanoes and a variety of complex shale diapirs. Observed reflectivity and seismic fabrics are discussed to infer clay composition, fluid content and type, and temperature.

Description: Highlights • Ocean current plays an essential role in shaping ocean floor. • Observed Kuroshio Current in the Kenting Plateau is up to 1.8 m/s. • Intense Kuroshio Current shaped the Kuroshio Knoll into flat topped elevated surface. • The parent rocks of the gravels were buried 2 to 4 km below the seafloor. • Decrease in grain size and sand content away from the Plateau indicates the Plateau acts as source for the sand. The Kenting Plateau is characterized by unusual low relief surfaces that straddle the topographic crest of the northern Manila accretionary prism off southern Taiwan at 400–700 m water depth. Multibeam bathymetric data, reflection seismic data, Acoustic Doppler Current Profiler (ADCP) data, surface grab samples, and sediment cores were collected in and around the Plateau to identify evidence of erosion in the Kenting Plateau and understand how the morphological evolution has been influenced by submarine erosion over geological time scales. The most distinctive feature on the Kenting Plateau is a 3 km × 7 km bean-shaped flat elevated platform (Kuroshio Knoll) revealed by multibeam bathymetry. Seismic data show almost no reflections beneath the seafloor and erosional truncations at the seafloor, especially in the Plateau's eastern half, evidencing widespread erosion. The P-wave velocity of the gravels recovered from the top of the Plateau ranges from 2.2 to 4 km/s. After comparing the velocity with the borehole data from nearby basin the burial depth of the parent rocks was found to be around 2 to 4 km below the seafloor, indicating that the parent rocks have been uplifted and gravels were formed due to erosion of the Plateau. The truncation of the seafloor shown on seismic sections suggests significant erosion on the Plateau. Sand content of the sediment cores decreases away from the Plateau, suggesting that sediment transport is effective in this area with high energy deposition, thereby accumulating coarse sediments on the Plateau and removing fine particles away from it. The presence of a dune field migrating northward of the Plateau, parallel to the Kuroshio Current also evidences active sediment transport in the area. Flow velocity of the Kuroshio Current observed from the ADCP data is very high, reaching up to 1.8 m/s on top of the Kuroshio Knoll (SE domain). We thus interpret that the observed intense erosion is caused by the Kuroshio Current, while the uplift of the Kenting Plateau is partially due to isostatic rebound caused by sediment removal through erosion and compression of the accretionary wedge. The higher sedimentation rate and coarser in grain size during sea level lowstand (20,000–12,000 yrs. BP) suggests that the erosion was more intense during the glacial period compared to that of deglacial period (〈 12,000 yrs. BP) as seen from the MD97–2145 core. Submarine erosion is predominant throughout the Plateau, and it controls the geomorphology of the Plateau, especially the Kuroshio Knoll.

Description: We used a combined ion pairing - organic matter speciation model (NICA-Donnan) to predict the organic complexation of iron (Fe) at ambient pH and temperature in the Celtic Sea. We optimized our model by direct comparison with Fe speciation determined by Adsorptive Cathodic Stripping Voltammetry using the added Fe-binding ligand 1-nitroso-2-naphthol (HNN) in the presence and absence of natural organic matter. We compared determined Fe speciation with simulated titrations obtained via application of the NICA-Donnan model with four different NICA parameter sets representing a range of binding site strengths and heterogeneities. We tested the assumption that binding sites scale to dissolved organic carbon (DOC) concentrations in marine waters. We found that a constant low DOC concentration resulted in an improved fit of our titration data to the simulated titrations, suggesting that inputs of autochthonous marine DOM may not increase the heterogeneity or concentrations of Fe binding sites. Using the optimal parameter set, we calculated pFe(III)´ (−log(∑Fe(OH)i3−i)) and apparent Fe(III) solubility (SFe(III)app) at ambient pH and temperature in the water column of the Celtic Sea. SFe(III)app was defined as the sum of aqueous inorganic Fe(III) species and Fe(III) bound to DOM formed at a free Fe (Fe3+) concentration equal to the limiting solubility of Fe hydroxide (Fe(OH)3(s)). SFe(III)app was within range of the determined dissolved Fe concentrations observed after winter mixing on the shelf and in waters 〉1500 m depth at our most offshore stations. Our study supports the hypothesis that the ocean dissolved Fe inventory is controlled by the interplay between Fe solubility and Fe binding by organic matter, although the overall number of metal binding sites in the marine environment may not be directly scalable to DOC concentrations.

Description: Highlights • full constitutive model parameter set of marine soil for MCC. • workflow for studies of potential trigger mechanisms exemplified by marine gas occurrence. • quantitative estimation of slope stability (by FOS) on the Balearic Promontory. • Gassy soil can be considered a preconditioning factor, not a trigger mechanism. Abstract The destructive potential of submarine landslides for populated coastal areas and maritime infrastructure has been described many times. However, the geological processes that can trigger such landslide events have not yet been fully established. In order to be able to conclusively assess the trigger potential of these processes, a quantification of the slope stability is indispensable. This requires a precise knowledge of the geotechnical and geological boundary conditions before and after the investigated landslide event, as well as the change in these boundary conditions caused by the alleged trigger mechanism. In order to make these described preconditions and the work process generally applicable, a universally adaptable methodology for the identification of trigger mechanisms was developed. Here it is successfully applied to marine gas occurrence, which has recently been considered as a trigger mechanism due to the negative influence of enclosed gas bubbles on the shear strength of fine-grained soils. The constitutive model by Sultan and Garziglia (2014) is applied to simulate the gas-influenced undrained shear strength of a marine soil from a sediment starved margin on the Balearic Promontory and a range of Finite Element Limit Analyses (FELA) are conducted to determine the resulting loss of stability of different slope geometries. Within the scope of these calculations, the first set of Modified Cam Clay model parameters for a soil from the western Mediterranean is introduced. Based on the simulations, it can be concluded that marine gas occurrence decreases the overall stability of a slope compared to the saturated state. However, it also becomes obvious that the prevailing slope geometries with low inclinations are stable with a substantial capacity reserve for all simulated scenarios. Conclusively, gassy soil can be designated as a preconditioning factor decreasing the slope stability, as the state of failure can only be reached if the slope was in a precarious state before, or in combination with other impacts.

Description: Highlights: • A first standardized and publicly available Holocene relative sea-level database for the Baltic Sea is presented. • The database holds 1099 revised data points with an estimation of vertical and chronological uncertainties. • Negative RSL tendencies prevail over the positive and complex tendencies in the Baltic Sea Basin. • Mid-Holocene RSL highstand occurred around 7.5–6.5 ka BP being consistent with the end of the final melting of the LIS. • The contribution of ice loading in the eastern Baltic Sea Basin is likely overestimated in the ICE-5G and ICE-6G_C models. Abstract: We present a compilation and analysis of 1099 Holocene relative shore-level (RSL) indicators located around the Baltic Sea including 867 relative sea-level data points and 232 data points from the Ancylus Lake and the following transitional phase. The spatial distribution covers the Baltic Sea and near-coastal areas fairly well, but some gaps remain mainly in Sweden. RSL data follow the standardized HOLSEA format and, thus, are ready for spatially comprehensive applications in, e.g., glacial isostatic adjustment (GIA) modelling. We apply a SQL database system to store the nationally provided data sets in their individual form and to map the different input into the HOLSEA format as the information content of the individual data sets from the Baltic Sea area differs. About 80% of the RSL data is related to the last marine stage in Baltic Sea history after 8.5 ka BP (thousand years before present). These samples are grouped according to their dominant RSL tendencies into three clusters: regions with negative, positive and complex (transitional) RSL tendencies. Overall, regions with isostatic uplift driven negative tendencies dominate and show regression in the Baltic Sea basin during the last marine stage. Shifts from positive to negative tendencies in RSL data from transitional regions show a mid-Holocene highstand around 7.5–6.5 ka BP which is consistent with the end of the final melting of the Laurentide Ice Sheet. Comparisons of RSL data with GIA predictions including global ICE-5G and ICE-6G_C ice histories show good fit with RSL data from the regions with negative tendencies, whereas in the transitional areas in the eastern Baltic, predictions for the mid-Holocene clearly overestimate the RSL and fail to recover the mid-Holocene RSL highstand derived from the proxy reconstructions. These results motivate improvements of ice-sheet and Earth-structure models and show the potential and benefits of the new compilation for future studies.

Description: Highlights • Offshore CCS research & development making good progress in Scotland and wider UK. • Yet differing views between oil and gas developers and civil society on CCS. • Survey and interview research explores differences between stakeholders. • Respondents more familiar with CCS tend to see it as more necessary for mitigation. • CCS most likely to find stakeholder support for specific and/or localised uses. Although Scotland and the wider UK is making good progress with research and development towards deployment of offshore carbon capture and storage, there is increasing divergence in opinion on the necessity of CCS for meeting climate change targets. Oil and gas operators appear optimistic about the technical feasibility of CCS; whereas civil society and NGOs are increasingly vocal in their scepticism towards the necessity of CCS in a net-zero society. Given that operators’ expertise may be required to support offshore CO2 storage given their subsea experience, and that civil society is important in shaping government and public opinion, this divergence may be a challenge to offshore CCS deployment in the UK and elsewhere. The purpose of this paper is to evaluate the grounds on which oil and gas operators’ views on CCS differ from a wider range of stakeholders, through a survey and in-depth interviews. Our results show that people with more knowledge of CCS are more likely to support its deployment, and that strong belief in anthropogenic climate change is lower – albeit rising – among oil and gas respondents. Our results also show concern that the net-zero transition may have negative effects for carbon-intensive regions, and that storage expertise is the UK’s strongest skill set for CCS deployment. We suggest that across a range of stakeholders, the value of CCS is thus most likely to lie in specific applications (e.g. hydrogen) and/or very specific localities (e.g. places with existing subsurface knowledge and skills), rather than widespread deployment as a mitigation technology.

Description: Contamination by hazardous substances is one of the main environmental problems in the eastern Gulf of Finland, Baltic Sea. A trilateral effort to sample and analyse heavy metals (HMs), polycyclic aromatic hydrocarbons (PAHs), and organotins from bottom sediments in 2019–2020 were conducted along with harvesting historical data in Russian, Estonian and Finnish waters. We suggest that the input of organotins still occurs along the ship traffic routes. The tributyltin content exceeded the established quality criteria up to more than 300 times. High contamination by PAHs found near the ports, most likely originate from incomplete fuel incineration processes. The Neva River Estuary and Luga Bay might potentially suffer from severe cadmium contamination. The high ecological risk attributed to the HMs was detected at deep offshore areas. The simulated accumulation pattern qualitatively agrees with field observations of HMs in sediments, demonstrating the potential of numerical tools to tackle the hazardous substances problems.

Description: Maritime activities in the subarctic and Arctic Ocean are predicted to substantially increase in the future due to climate change and declining sea ice cover. Inevitably, the consequences will be seen in impacts on marine ecosystems in this region at many different levels, such as increased pollution load due to antifouling biocides, polycyclic aromatic hydrocarbons, metals and pharmaceuticals. Here we discuss the current situation and evaluate the effect of increased shipping on the environmental status of subarctic and Arctic waters, in relation to elevated loads of both legacy and emerging pollutants in the region. It is of high importance to evaluate the current levels of selected pollutants, which will most likely rise in near future. Furthermore, it is important to improve our understanding of the effects of these pollutants on marine organisms at high latitudes, as the pollutants may behave differently in cold environments compared to organisms at lower latitudes, due to dissimilar physiological responses and adaptations of the cold-water organisms. Integrative studies are needed to better understand the impact of pollutants on the marine fauna while monitoring programmes and research should be continued, with an increased capacity for emerging pollutants of concern.

Description: The presence of secondary phases (carbonates, zeolites, clay minerals, etc.) in volcanic rocks and subabyssal intrusive units (sills and dykes) often pose obstacles for high resolution 40Ar/39Ar geochronology as these phases may promote loss of radiogenic argon, production of interfering isotopes, or trapping of excessive atmospheric argon contents. Acid treatment is used to remove alteration products before sample irradiation and analysis. In an effort to assess and quantify the effects of alteration and the removal of alteration products by acid treatment on the accuracy and precision of 40Ar/39Ar analysis, three basalt samples from the Paraná large igneous province previously dated in triplicate without acid treatment were dated again without and with acid treatment. Despite the presence of 14–28% clay minerals in the samples, which results in up to 67% atmospheric component in the total amount of 40Ar extracted from untreated grains, the presence of alteration phases and their removal by acid treatment have no significant role on the accuracy of 40Ar/39Ar step-heating ages. The only quantifiable effect is an ~0.1% increase in age precision for the acid-treated aliquots. The results reveal that effective separation of atmospheric and radiogenic gases in properly designed and sufficiently detailed step-heating experiments successfully obviates deleterious effects associated with some types of alteration phases, and it suffices to produce high-resolution ages. Therefore, acid treatment is a desirable but not essential step in high-resolution 40Ar/39Ar geochronology. Characterizing alteration phases, however, is an essential step as some secondary products (e.g., sericite, albite), if present, will not be leached during acid treatment and will significantly affect the accuracy of geochronological results either with or without acid treatment.

Description: Highlights: • Lake Asal (Afar Rift) is fed by seafloor-type hydrothermal fluids. • An oceanic “embryo” in arid climate is mildly acidic and metal rich. • It has heavy C, O and Ca, and light Zn isotope composition. • Lake chemistry is controlled by hydrothermal discharge and aeolian input. Abstract: At the place where the submarine Aden Ridge encroaches on the African continent and interacts with the East African Rift system, two small basins form: Ghoubbet-al-Kharab and Lake Asal. Whereas Ghoubbet-al-Kharab is connected to the open ocean, Lake Asal is a typical example of oceanic “embryo”, which is defined as a system that is detached from the ocean, but has features of a marine basin with an oceanic type crust and a seawater-based water body. In order to shed light on the source of water, type of hydrothermal activity and hydrothermal deposits, and controls on the water chemistry in an oceanic “embryo”, we undertook a mineralogical-geochemical study of the lake water, hydrothermal fluids and hydrothermal carbonate deposits of Lake Asal. The geochemical analyses of lake water and hydrothermal fluids show that Lake Asal (located in an arid zone with strong evaporation and with no riverine input) is fed by seafloor-type hydrothermal fluids according to the following scenario: percolation of seawater along faults and cracks of extension in the rift, reaction of seawater with the hot basaltic rocks and hydrothermal fluid generation, discharge of the hydrothermal fluid in the Asal depression and accumulation of the Lake Asal water body. The fluid venting at the Lake Asal bottom is a mixture of 97% end-member hydrothermal fluid and 3% lake water. The calculated end-member hydrothermal fluid of this oceanic “embryo” is poorer in metals than the seafloor hydrothermal fluids of an open and evolved ocean. In addition to the seawater/rock interaction, the chemistry of Lake Asal is also controlled by evaporation leading to hyper salinity. In a hyper saline water body a number of hydrothermally supplied metals are stabilized as chloride complexes and accumulate. This results in a metal rich and mildly acidic “embryonic” ocean. Unlike an open and evolved modern ocean, the “embryonic” ocean located in an arid zone has heavy C and O isotope composition and light Zn and Fe isotope composition. Calcium isotope compositions of both types of ocean are similarly heavy. There are two genetically different sources of elements to the Lake Asal that are vertically separated: hydrothermal (lower, or bottom) and aeolian (upper, or surficial). Another important control on the lake water chemistry is the formation of carbonate spires at the lake bottom. Ca‑carbonate precipitation immobilizes substantial amount of hydrothermally supplied Ca and drives up the (Mg/Ca)mol of the lake water. Increasing (Mg/Ca)mol of the evolving lake water leads to changes in the mineralogy of spires: from low-Mg calcite to aragonite. Thus, the spire formation exerts a self-control on its mineralogy. Carbonate spire deposition affects also the Ca, Zn and Fe isotope composition of the lake water through adsorption or/and co-precipitation induced isotope fractionation.

Description: Highlights: • Aquatic invasions have cost the global economy US$345 billion. • Most costs are caused by invertebrates, in North America and damages to resources. • Costs have increased exponentially over time, to at least US$23 billion in 2020. • Aquatic invasion costs are underrepresented compared to terrestrial invasion costs. • Taxonomic, geographic and temporal gaps make these costs severely underestimated. Abstract: Much research effort has been invested in understanding ecological impacts of invasive alien species (IAS) across ecosystems and taxonomic groups, but empirical studies about economic effects lack synthesis. Using a comprehensive global database, we determine patterns and trends in economic costs of aquatic IAS by examining: (i) the distribution of these costs across taxa, geographic regions and cost types; (ii) the temporal dynamics of global costs; and (iii) knowledge gaps, especially compared to terrestrial IAS. Based on the costs recorded from the existing literature, the global cost of aquatic IAS conservatively summed to US$345 billion, with the majority attributed to invertebrates (62%), followed by vertebrates (28%), then plants (6%). The largest costs were reported in North America (48%) and Asia (13%), and were principally a result of resource damages (74%); only 6% of recorded costs were from management. The magnitude and number of reported costs were highest in the United States of America and for semi-aquatic taxa. Many countries and known aquatic alien species had no reported costs, especially in Africa and Asia. Accordingly, a network analysis revealed limited connectivity among countries, indicating disparate cost reporting. Aquatic IAS costs have increased in recent decades by several orders of magnitude, reaching at least US$23 billion in 2020. Costs are likely considerably underrepresented compared to terrestrial IAS; only 5% of reported costs were from aquatic species, despite 26% of known invaders being aquatic. Additionally, only 1% of aquatic invasion costs were from marine species. Costs of aquatic IAS are thus substantial, but likely underreported. Costs have increased over time and are expected to continue rising with future invasions. We urge increased and improved cost reporting by managers, practitioners and researchers to reduce knowledge gaps. Few costs are proactive investments; increased management spending is urgently needed to prevent and limit current and future aquatic IAS damages.

Description: Highlights • The revised minimum subduction initiation age for the Aleutian system is 48 Ma. • The evolution of the arc was characterized by three distinct magmatic pulses. • The types of magmas erupted appear to have changed during the arc evolution. In order to further constrain the timing of the Aleutian Arc initiation as well as its early evolution, an extensive 40Ar/39Ar dating and geochemical (major and selected trace elements) campaign (40 samples) of the lower units of the Aleutian ridge has been carried out on samples dredged from deep fore-arc canyons and rear arc tectonic structures. The new dataset slightly increases the minimum inception age for the Aleutian system, with the two oldest samples dated at 46.1 ± 3.3 Ma and 47.80 ± 0.57 Ma. Both mid Eocene ages were obtained on tholeiitic mafic volcanic rocks from the western section of the arc. The new data also support the occurrence of three distinct periods of enhanced magmatic activity (magmatic pulses) during the pre-Quaternary evolution of the arc (at 38–27, 16–11 and 6–0 Ma), as previously suggested based on a more limited and dominantly subaerial dataset. Moreover, the data refine the duration of the first pulse of activity, which ended 2 Ma later than previous estimates. The first and last pulses may be associated with rotations of the subducting plates while the second pulse might result from regional tectonic changes. The significant overlap between the age distribution of the submarine and subaerial samples suggests that much of the earlier parts of the arc may have been uplifted and subaerially exposed. The expected crustal growth associated with the pulses is unlikely to have significantly impacted magmatic residence times, since no variation in the degree of differentiation of the rocks can be observed during or after the pulses. On the other hand, the type of magmas erupted may have changed during the arc evolution. Prior to the first pulse, activity appears to have been dominantly tholeiitic. On the other hand, the first pulse was characterized by coeval tholeiitic, transitional and calc-alkaline magmas, with calc-alkaline activity increasing after the first ~3 Ma. Subsequently, a dominantly calc-alkaline period occurred from 29 to 8 Ma, followed by a progressive return of coeval tholeiitic, transitional and calc-alkaline activity. These temporal changes in magma types correspond to likely variations in arc crustal thickness beneath the active front, and could therefore be a response to physical changes of the overriding plate.

Description: The neodymium isotope composition (ɛNd) of authigenic phases in marine sediment is widely used to reconstruct the origin and mixing of water masses of overlying seawater through time. However, at some locations in the modern ocean, the ɛNd of authigenic phases in surface sediment is not consistent with that of local seawater, raising concerns about its current interpretation as a paleotracer of water masses. To further investigate this question, we conducted a laboratory-based incubation experiment with a Mn-oxide phase placed at the sediment–water interface of multicores to assess the extent to which the authigenic phase records seawater ɛNd. Multicores were collected from the Strait of Georgia (SoG), which is a relatively deep coastal waterway with high sedimentation rates, oxygenated surface sediments, and active macrofauna, separating the mainland coast of British Columbia and Vancouver Island. Manganese oxide-coated XAD resin beads were placed at the sediment surface and the cores were incubated for 6 months in a tank filled with SoG seawater spiked with Nd. While the ɛNd of the Mn-oxide coated resin (−4.0) was similar to that of SoG seawater used for the incubation (−3.7), the Nd/Nd of the Mn-oxide phase measured after the incubation indicates that, under our experimental conditions, a minimum of 83% of the Nd associated with the Mn-oxide phase is not sourced from seawater, but from pore water. The Nd/Nd ratio of the Mn-oxide resin is necessary to determine the predominant source of Nd to the resin because the ɛNd of SoG pore water (−3.9) is within analytical error of seawater (−3.7). Using field data and constraints from the Nd mass balance during the incubation, we conclude that the similarity of ɛNd in pore water and seawater in the SoG is fortuitous and not a result of a top-down or bottom-up control. Although the setting of our sediments is not directly comparable to open ocean locations, this study raises concerns about the use of ɛNd in paleocirculation studies, and points to the necessity of elucidating the factors controlling local lithogenic dissolution in pore waters as a prerequisite for the correct interpretation of ɛNd in the authigenic phases of marine sediments.

Description: Highlights • Fermentation, methanogenesis and methanotrophy prevail at the As-contaminated site. • Reducing aquifer consists of gray sediment and is dominated by Fe(III) (oxyhydr)oxides and As(III). • Less reducing aquifer consists of yellow-brown sediment and is dominated by goethite and As(V). • Anaerobic CH4 oxidation likely supports carbonate mineral formation. • Methanotrophic Fe(III)-reducer Ca. Methanoperedens coincides with As and Fe peaks in sediments. High arsenic (As) concentrations in groundwater are a worldwide problem threatening the health of millions of people. Microbial processes are central in the (trans)formation of the As-bearing ferric and ferrous minerals, and thus regulate dissolved As levels in many aquifers. Mineralogy, microbiology and dissolved As levels can vary sharply within aquifers, making high-resolution measurements particularly valuable in understanding the linkages between them. We conducted a high spatial resolution geomicrobiological study in combination with analysis of sediment chemistry and mineralogy in an alluvial aquifer system affected by geogenic As in the Red River delta in Vietnam. Microbial community analysis revealed a dominance of fermenters, methanogens and methanotrophs whereas sediment mineralogy along a 46 m deep core showed a diversity of Fe minerals including poorly crystalline Fe (II/III) and Fe(III) (oxyhydr)oxides such as goethite, hematite, and magnetite, but also the presence of Fe(II)-bearing carbonates and sulfides which likely formed as a result of microbially driven organic carbon (OC) degradation. A potential important role of methane (CH4) as electron donor for reductive Fe mineral (trans)formation was supported by the high abundance of Candidatus Methanoperedens, a known Fe(III)-reducing methanotroph. Overall, these results imply that OC turnover including fermentation, methanogenesis and CH4 oxidation are important mechanisms leading to Fe mineral (trans)formation, dissolution and precipitation, and thus indirectly affecting As mobility by changing the Fe-mineral inventory.

Description: Highlights: We advocate to shift research efforts in environmental biotechnology from searching for desired traits of monocultures to that of microbial communities. As these traits will be hard to identify with classical genome mining approaches, we recommend using artificial community selection as a tool to identify and to select for novel and/or enhanced functions. Bioremediation and biodegradation with artificially selected microbial communities harbors great potential to become a fast, cost-effective, eco-friendly, and socially acceptable way to remove pollutants without prior knowledge of the involved species and degradation pathways needed. The use of highly integrated multispecies microbial communities instead of monocultures in biodegradation processes will result in more stable and more productive cultures. The novelty of our proposed approach lies in the combination of eco-evolutionary principles with applied biotechnology. This will stimulate new advancements in environmental biotechnology, and will likely result in the discovery of novel metabolic degradation pathways. Environmental accumulation of anthropogenic pollutants is a pressing global issue. The biodegradation of these pollutants by microbes is an emerging field but is hampered by inefficient degradation rates and a limited knowledge of potential enzymes and pathways. Here, we advocate the view that significant progress can be achieved by harnessing artificial community selection for a desired biological process, an approach that makes use of eco-evolutionary principles. The selected communities can either be directly used in bioremediation applications or further be analyzed and modified, for instance through a combination of systems biology, synthetic biology, and genetic engineering. This knowledge can then inform machine learning and enhance the discovery of novel biodegradation pathways.

Description: In 2016, the research ice-breaker Polarstern surveyed the submerged peaks of the permanently ice-covered Langseth Ridge, a tectonic feature comprising the Karasik seamount and two deeper seamount peaks, abutting the Gakkel ultra-slow spreading ridge (87°N 62°E to 85.5°N 57.4°E)1. A towed marine camera sled and a hybrid remotely operated vehicle revealed these peaks to be covered by a dense demosponge community, at first glance reminiscent of North Atlantic Geodia grounds (sensu2). Sponges were observed on top of a thick layer of spicule mat (Figure 1 and Video S1), intermixed with underlying layers of empty siboglinid tubes and bivalve shells, a substrate covering almost the entire seafloor. We observed trails of densely interwoven spicules connected directly to the underside or lower flanks of sponge individuals (Figure 1), suggesting these trails are traces of motile sponges. This is the first time abundant sponge trails have been observed in situ and attributed to sponge mobility. Given the low primary production in this permanently ice-covered region, these trails may relate to feeding behavior and/or a strategy for dispersal of juveniles. Such trails may remain visible for long periods given the regionally low sedimentation rates.

Description: Bottom conditions in deep sea basins are strongly connected to the health of marine ecosystems. Due to its enclosed location and shallow bathymetry, the Baltic Sea is very sensitive to eutrophication and climate change. The primary objective of this study is to describe long-term variability of near-bottom oxygen concentration, salinity, and temperature in three basins of the Southern Baltic: the Bornholm Basin (BB), Slupsk Furrow (SF), and Gdansk Deep (GD) based on the analysis of historical hydrographic data, and to demonstrate the impact of inflow events on deep ventilation in those basins. Mean bottom oxygen concentration in the period 1946–2016 was very similar in the deep basins (1.2–1.4 ml l−1), and much higher in the shallower SF (3.2 ml l−1) due to the water mass modification occurring between BB and SF. SF was found to contribute to the ventilation of GD with a 1–3-month lag. The results indicate that vertical mixing in SF and the eastward advection of ventilated waters towards GD directly influence bottom water properties in GD. Therefore, next to Major Baltic Inflows (MBIs), also weaker barotropic and baroclinic inflows are important for the bottom ventilation in this area. The long-term trends are very similar in all of the basins. Near-bottom oxygen gradually decreased from 1946, reaching a minimum in 2000. This coincided with salinity and temperature minimums and was linked to reduced frequency and volume of barotropic inflows due to their decadal variability. Oxygen concentrations have been slowly recovering in all three basins since 2000. At the end of the record, their 5-year mean values were approximate to the levels from the 1970's. In the period 1946–2016, hypoxia (oxygen concentration below 2 ml l−1) occurred more frequently in BB (78%) than in GD (73%). Although the results show slow recovery of dissolved oxygen concentrations based on 5-year long mean values, the occurrence of hypoxia increased over the last two decades, reaching 85% in BB and GD and 24% in SF. Mean and decadal variability of the seasonal cycle of near-bottom water properties were analysed. Mean annual cycles of bottom oxygen in three basins are approximately sinusoidal, with the highest values occurring in March, and lowest in September. The range of the mean oxygen seasonal cycle decreases eastward from 1.6 ml l−1 in BB, through 1.3 ml l−1 in SF, to 1.2 ml l−1 in GD. Furthermore, between 1946–1980 and 1995–2016, the range of the mean DO seasonal cycle decreased by 0.2 ml l−1 in BB, 0.6 ml l−1 in SF, and 0.4 ml l−1 in GD. In BB and SF, minimum bottom temperatures occur in summer, and maximum in winter. The strongest annual temperature variation (3 °C) occurs in SF, and is smaller in BB (1.5 °C) and GD (1 °C). The amplitude of the seasonal salinity variation is approximately 0.5 psu in all basins. In BB and GD, a drop in salinity is observed in autumn.

Description: Highlights: • Thermal biology of rock-pool and pan specialist branchiopods were contrasted. • Wetland type was not a good predictor of branchiopod thermal preference/limits. • Spinicaudatans preferring higher temperatures than anostracans. • Spinicaudatans were more tolerant of high temperatures than anostracans. • Anostracans may be more susceptible to projected climatic warming. Abstract: Large branchiopods are specialist crustaceans adapted for life in temporary, thermally dynamic wetland ecosystems. Certain large branchiopod species are, however, restricted to specific temporary wetland types, exemplified by their physico-chemical and hydroperiod characteristics. Here, we contrasted the thermal preference and critical thermal maxima (CTmax) and minima (CTmin) of southern African anostracans and spinicaudatans found exclusively in either temporary rock-pool or pan wetland types. We hypothesized that environment of origin would be a good predictor of thermal preference and critical thermal limits. To test this, Branchiopodopsis tridens (Anostraca) and Leptestheria brevirostris (Spinicaudata) were collected from rock-pool habitats, while Streptocephalus cafer (Anostraca) and a Gondwanalimnadia sp. (Spinicaudata) were collected from pan habitats. In contrast to our hypothesis, taxonomic relatedness was a better predictor of CTmax and temperature preference than environment of origin. Spinicaudatans were significantly more tolerant of high temperatures than anostracans, with L. brevirostris and Gondwanalimnadia sp. median CTmax values of 45.1 °C and 44.1 °C, respectively, followed by S. cafer (42.8 °C) and B. tridens (41.4 °C). Neither environment or taxonomic relatedness were good predictors of CTmin trends, with B. tridens (0.9 °C) and Gondwanalimnadia sp. (2.1 °C) having the lowest median CTmin values, followed by L. brevirostris (3.4 °C) and S. cafer (3.6 °C). On the contrary, temperature preferences differed according to taxa, with spinicaudatans significantly preferring higher temperatures than anostracans. Leptestheria brevirostris and Gondwanalimnadia sp. both spent most time at temperatures 30–32 °C, S. cafer at 18–20 °C and B. tridens at 21–23 °C. Constrained thermal traits reported here suggest that the studied anostracans might be more susceptible to projected climatic warming than the spinicaudatans, irrespective of habitat type, however, these taxa may also compensate through phenotypic plasticity.

Description: Highlights • First comprehensive geochemical and geochronological data from the 85°E Ridge. • The volcanism of the southern 85°E Ridge is age progressive. • The southern 85°E Ridge is characterized by an enriched mantle one (EMI) signature. • EMI flavor derives most likely from shallow recycled continental material. • Conrad Rise and the Afanasy Nikitin Plateau most likely share a co-genetic origin. Abstract Age-progressive volcanic chains are generally considered as surface expressions of deep-rooted mantle plumes, whereas non-age progressive volcanic groups or solitary volcanic edifices are generally attributed to shallow sources. The Buried Hills, Partly Buried Hills, Afanasy Nikitin Rise and newly discovered Southern Seamount Chain, located between the Kerguelen and Reunion hotspot tracks in the Indian Ocean, form the curved and discontinuous 85°E volcanic track. With the exception of the Afanasy Nikitin Rise, characterized by the most enriched mantle one (EMI) compositions in an ocean basin, no other parts of this volcanic track have been previously sampled. Although some models favor a hotspot origin for the 85°E Ridge track associated with the Crozet, Marion or Conrad Rise plumes, its origin remains highly controversial. We report new 40Ar/39Ar age and geochemical (major, trace element and Sr-Nd-Pb-Hf isotope) data from the 85°E Ridge. Our age data display a progression of decreasing ages (82–66 Ma) from the north to south, suggesting formation by a relatively stationary sub-lithospheric melt anomaly. The geochemistry of the 85°E Ridge can be explained by mixing of Indian-type plume material with Indian mid-ocean-ridge basalt (MORB) and detached continental lithospheric (mantle and/or lower crustal) material in the upper mantle. Plate reconstructions demonstrate that the southern portion of the 85°E Ridge and Conrad Rise could be derived from the Conrad Rise hotspot/plume. A weak, pulsating mantle plume could explain the weak morphological expression and intermittent nature of this hotspot track, compared to Reunion and Kerguelen tracks.

Description: The Intergovernmental Panel on Climate Change assessments (IPCC) Special Report on 1.5 °C of global warming is clear. Nearly all pathways that hold global warming well below 2 °C involve carbon removal (IPCC, 2015). In addition, solar geoengineering is being considered as a potential tool to offset warming, especially to limit temperature until negative emissions technologies are sufficiently matured (MacMartin et al., 2018). Despite this, there has been a reluctance to embrace carbon removal and solar geoengineering, partly due to the perception that these technologies represent what is widely termed a “moral hazard”: that geoengineering will prevent people from developing the will to change their personal consumption and push for changes in infrastructure (Robock et al., 2010), erode political will for emissions cuts (Keith, 2007), or otherwise stimulate increased carbon emissions at the social-system level of analysis (Bunzl, 2008). These debates over carbon removal and geoengineering echo earlier ones over climate adaptation. We argue that debates over “moral hazard” in many areas of climate policy are unhelpful and misleading. We also propose an alternative framework for dealing with the tradeoffs that motivate the appeal to “moral hazard,” which we call “risk-response feedback.”

Description: The numerous chemical and isotopic studies of oceanic basalts have shaped our perception of mantle geochemistry over the last six decades. As partial melts of Earth’s mantle, basalts are indirect tracers of mantle composition. Because the scale of isotopic heterogeneity is smaller than the scale of melt production, melts from isotopically heterogeneous mantle ingredients mix into variable blends on their way to eruption. Basalts are therefore isotopically less variable than their mantle sources. Decrypting “the message from oceanic volcanism” thus necessitates developing strategies to see through this ubiquitous sampling bias, but also acknowledging the inherent limitations imposed by investigating mantle composition through basalts. Understanding how large the bias between melts and mantle actually is requires decoding process versus source-related causes for the isotopic variability of basalts. Ultimately, deciphering the effective range of isotopic variability in Earth’s mantle is crucial for connecting isotopic signals in basalts to different materials and thus, the geologic processes that govern silicate earth evolution. Invariably, however, basalts are weighted averages of melts from isotopically different mantle constituents. As such, their incompatible element and isotopic composition is inherently biased towards the incompatible element enriched source components. The incompatible element depleted components of Earth’s mantle must therefore range to more extreme compositions than the basalts. But although isotope data from peridotites and olivine-hosted melt inclusions have extended the bounds of mantle heterogeneity, the overall extent of incompatible element depletion and mass fraction of incompatible element depleted mantle is still elusive. Mantle depletion is driven by the rate of melt extraction, or mantle processing, and thus interconnects the geochemical and geodynamical evolution of Earth’s mantle. Better constraining mantle depletion is therefore at the root of understanding our planet’s principal mode of operation.

Description: Seep carbonates tell us where and when CH4-charged fluids escaped from the subsurface, thus providing qualitative information to reconstruct the activity of petroleum systems. The potential of seep carbonates as quantitative proxies for the amount of CH4 leaked, however, remains largely unexplored, which limit their applicability as exploration tools. This paper tackles the quantification of the CH4 flux - seep carbonate relationship by simulating the coupled sedimentary carbon (C) – sulfur (S) cycles in a reaction-transport modeling (RTM) framework. We first establish a theoretical basis demonstrating that the stoichiometry of diagenetic reactions and the ambient pH of pore waters are the main drivers of the rate of change in the saturation state of carbonate minerals (ΩCal), while the concentrations of total dissolved inorganic carbon and sulfide are only of secondary importance. It results that anaerobic oxidation of methane (AOM) is the main driver of carbonate precipitation, while organoclastic sulfate reduction (SR) has a minor impact. We further show that SR mostly drives carbonate dissolution, but can also contribute to precipitation when pH is low (〈7–7.1). The RTM simulations reveal that an increase in upward fluid flow triggers an intensification of peak AOM rates, associated to a shallowing and thinning of the zone of carbonate precipitation. Such behavior leads to an almost linear relationship between the amount of carbonate precipitated and flux of CH4 (nCH4 = 3.3–5.2 * nCaCO3), until, eventually, full cementation occurs. We thus define a “quantitative domain” at moderate fluid flow and a “threshold domain” at high fluid velocities, where full cementation solely provides a lower bound estimate of the amount of CH4 leaked. We also show that in contrast to a traditional view of seep carbonate formation mainly controlled by venting activity, sedimentation rate and water depth also play major roles, via their control on residence time and saturation concentration of CH4, respectively. The interpretation of vertical seep carbonate stacks should thus not solely focus on changes in fluid flow, but also consider changes in sedimentation rate and/or water depth.

Description: An understanding of how the coupled cycles of carbon, iron and sulfur in sediments respond to environmental change throughout Earth history requires the reconstruction of biogeochemical processes over a range of spatial and temporal scales. In this study, sediment cores from the southwestern Black Sea were analyzed to gain insight into past changes in biogeochemical processes with particular focus on the cycling of dissolved organic carbon (DOC). The sediment consists of Late Pleistocene deposits of iron oxide-rich and organic-poor lacustrine sediments, a Holocene sapropel layer deposited after the inflow of saline Mediterranean seawater about 9300 yr BP, and overlying recent marine sediments. The porewaters displayed high concentrations of DOC, acetate, dissolved iron and an extended depth interval over which sulfate and methane were both present. The historical fluctuations of the fluxes of carbon, sulfur and iron species at the seafloor that led to these present-day geochemical profiles, and which cannot be easily interpreted from the measured data alone, were hindcasted with a reaction-transport model. The model suggests that the inflow of Mediterranean seawater impacted the rain rate and reactivity of organic matter reaching the sediments, which shifted the sedimentary redox regimes throughout the Holocene that now are reflected on different lithology units. Organic matter in the sapropel layer is apparently the main source of modern-day accumulations of DOC and acetate, both of which probably sustained subsurface microbial activity throughout the post-glacial period. The ratio between DOC and dissolved inorganic carbon (DIC) flux to the bottom water decreased from ∼40% before the inflow of Mediterranean water to ∼2% at the present day. We suggest that the coexistence of methanogenesis and sulfate reduction was associated with sulfate-reducing bacteria and methanogens sharing common substrates of acetate and lactate and utilizing non-competitive substrates such as methylated compounds in the sapropel layer and in the bottom of modern marine deposits. Intense sulfur and iron cycling mainly took place in the organic-poor freshwater deposits, today characterized by high concentrations of dissolved iron and methane. In contrast to previous studies in similar environments, anaerobic oxidation of methane coupled to the reduction of ferric iron was negligible. The results have broad implications for coastal environments that are currently experiencing deoxygenation and seawater intrusion and also for understanding the role of DOC in the sedimentary carbon cycle.

Description: The stable downward continuation is an important and difficult problem in magnetic data processing and interpretation. The downward continuation of the magnetic field is an unstable process, wherein high-frequency signals will be rapidly amplified and overwhelm useful signals. Although the suppression of high-frequency signals can allow for the acquisition of smooth downward continuation results, this will lead to a loss of amplitude in the data. Therefore, it remains challenging to reproduce the amplitude and shape of a magnetic anomaly well synchronously. Based on the good performance of the dual-layer equivalent source method when processing magnetic data, a stable and high precision downward continuation approach is proposed. The synthetic data tests show that the proposed approach can obtain results with a high accuracy. Notably, this new technique provides a stable scheme for the downward continuation of the magnetic anomaly field. Application of the approach to aeromagnetic data helps to verify the stability of the proposed method.

Description: Assessing the N content of arc magmas and their mantle source remains a challenge because the volatile element composition of melts and gases can be modified during magma ascent, storage, and eruption. Given that melt inclusions (MIs) in Mg-rich olivine represent the best proxies for primary arc melts, we applied, for the first time, an in situ high-resolution secondary ion mass spectrometry (SIMS) method to determine the N concentration in olivine-hosted MIs from Klyuchevskoy volcano in Kamchatka. To reverse the effects of post-entrapment modification processes (i.e., exsolution of volatiles into a fluid bubble), the MIs were partially to completely homogenized at high temperatures (1150–1400 °C) and pressures ranging from 0.1 to 500 MPa under dry to H2O-saturated conditions at variable oxygen fugacities (CCO to QFM + 3.3). After the experiments, N concentrations in water-rich MI glasses correlate positively with H2O and CO2 contents as well as with N/CO2 ratios, and negatively with the volume of the remaining fluid bubble. Glasses of completely homogenized (fluid bubble-free) MIs contain up to 25.7 ± 0.5 ppm N, whereas glasses of three unheated (natural, bubble-bearing) MIs have significantly lower N concentrations of ~1 ± 0.3 ppm. The N-CO2-Nb characteristics of completely homogenized MIs indicate that melts feeding Klyuchevskoy volcano have high absolute concentrations of both N and CO2, as well as large excess of these volatiles relative to Nb, compared to primary mid-ocean ridge melts. This implies that large amounts of N and CO2 in Klyuchevskoy melts and their mantle source are derived from the subducting slab, and that these subducted volatiles are (partially) returned to the crust and atmosphere by arc-related magmatism.

Description: The Amazon River has the largest drainage basin in the world, making it a major source of trace elements and dissolved organic matter (DOM) to the Atlantic Ocean. However, despite the increasing anthropogenic impacts to the Amazon basin, few recent studies exist quantifying trace element data in this region. The aim of the study was to analyze the input and removal processes that influence the transport of Ni and Co species in the Amazon and Pará River estuaries and mixing zone. Toward this goal, this work provides a comprehensive mixing and speciation study for the trace elements Ni and Co. Samples were collected during a period of high river discharge on the RV Meteor cruise M147 (Amazon – GEOTRACES process study GApr11) in the Amazon and Pará River outflow regions, as well as the aging mixing plume to the north, a mangrove belt to the southeast and the North Brazil Current (NBC) seawater endmember. Here we present the results for labile particulate (〉0.2 μm), labile and total dissolved (〈0.2 μm), large colloidal (0.015–0.2 μm), soluble (〈0.015 μm) and ultrafiltered (〈1 and 〈 10 kDa) fractions of Ni and Co in surface waters (towed-fish) and along the water column at different depths (CTD) samples using comparative approaches by adsorptive cathodic stripping voltammetry (AdCSV) and inductively coupled plasma-mass spectrometry (ICP-MS). We observed good agreement between AdCSV and ICP-MS measurements for Ni, and to a lesser extent Co. In general, dissolved and soluble Ni and Co decreased with increasing salinity, however additional non-conservative removal was also observed and attributed to possible biological uptake and colloidal flocculation. Shipboard AdCSV measurements showed that dissolved Ni was present mostly in the “reactive” form as weak complexes, suggesting high bioavailability, while reactive dissolved Co was absent, indicating the presence of strong organic Co complexes. In both Ni and Co, an elevated colloidal fraction was observed at low salinity, suggesting removal of dissolved Ni and Co via colloidal flocculation upon seawater mixing, while the soluble species were transported to the Atlantic Ocean. At depth, the soluble phase dominated, and we observed concentration maxima at 500–1000 m, indicating the presence of Antarctic Intermediate Water (AIW) and possible biological regeneration. We also observed unique source signatures in dissolved and labile particulate Ni and Co species from the Amazon and Pará River outflow regions, in addition to a contribution from mangrove belt-associated groundwater.

Description: Highlights: • The epoch of the Anthropocene, a period during which human activity has been the dominant influence on climate and the environment, has witnessed a decline in oxygen concentrations and an expansion of oxygen-depleted environments in both coastal and open ocean systems since the middle of the 20th century. • This review paper provides a synthesis of system-specific drivers of low oxygen in a range of case studies representing marine systems in the open ocean, on continental shelves, in enclosed seas and in the coastal environment. • Identification of similar and contrasting responses within and across system types and corresponding oxygen regimes is shown to be informative both in understanding and isolating key controlling processes and provides a sound basis for predicting change under anticipated future conditions. • Case studies were selected to achieve a balance in system diversity and global coverage. • Each case study describes system attributes, including the present-day oxygen environment and known trends in oxygen concentrations over time. • Central to each case study is the identification of the physical and biogeochemical processes that determine oxygen concentrations through the tradeoff between ventilation and respiration. • Spatial distributions of oxygen and time series of oxygen data provide the opportunity to identify trends in oxygen availability and have allowed various drivers of low oxygen to be distinguished through correlative and causative relationships. • Deoxygenation results from a complex interplay of hydrographic and biogeochemical processes and the superposition of these processes, some additive and others subtractive, makes attribution to any particular driver challenging. • System-specific models are therefore required to achieve a quantitative understanding of these processes and of the feedbacks between processes at varying scales. Abstract: The epoch of the Anthropocene, a period during which human activity has been the dominant influence on climate and the environment, has witnessed a decline in oxygen concentrations and an expansion of oxygen-depleted environments in both coastal and open ocean systems since the middle of the 20th century. This paper provides a review of system-specific drivers of low oxygen in a range of case studies representing marine systems in the open ocean, on continental shelves, in enclosed seas and in the coastal environment. Identification of similar and contrasting responses within and across system types and corresponding oxygen regimes is shown to be informative both in understanding and isolating key controlling processes and provides a sound basis for predicting change under anticipated future conditions. Case studies were selected to achieve a balance in system diversity and global coverage. Each case study describes system attributes, including the present-day oxygen environment and known trends in oxygen concentrations over time. Central to each case study is the identification of the physical and biogeochemical processes that determine oxygen concentrations through the tradeoff between ventilation and respiration. Spatial distributions of oxygen and time series of oxygen data provide the opportunity to identify trends in oxygen availability and have allowed various drivers of low oxygen to be distinguished through correlative and causative relationships. Deoxygenation results from a complex interplay of hydrographic and biogeochemical processes and the superposition of these processes, some additive and others subtractive, makes attribution to any particular driver challenging. System-specific models are therefore required to achieve a quantitative understanding of these processes and of the feedbacks between processes at varying scales.

Description: Oxygen depletion threatens an increasing number of shallow water environments, specifically habitats below the seasonal halocline in coastal settings of the Baltic Sea. To understand the natural variations of dissolved oxygen levels on seasonal and inter-annual time-scales prior to the instrumental era, high-resolution archives are urgently required. The present study evaluates the potential use of Mn/Ca values in shells of the bivalve, Arctica islandica to infer concentrations of past dissolved oxygen concentrations. This study is based on laser ablation – inductively coupled plasma – mass spectrometry (LA-ICP-MS) data of six contemporaneous specimens and demonstrates that background variations of shell Mn/Ca are inversely linked to dissolved oxygen concentrations in the water column (r = −0.68; R2 = 0.46, p 〈 0.0001), which in turn are coupled to the amount of dissolved Mn. The regular seasonal changes were superimposed by sharp Mn/Ca peaks, most likely resulting from the ingestion of a large amount of Mn-rich organic particles. The availability of such particles can increase due to the resuspension of food particles by strong bottom currents or alternatively, result from increased particle flux from surface waters after major river discharges and subsequent phytoplankton blooms. Besides sharp Mn/Ca peaks, often accompanied by sharp Ba/Ca peaks and increased shell growth rate. In addition, after exceptional major barotropic inflows from the North Sea, the biogeochemical steady-state conditions remained disturbed for up to ca. two years, because the redox-sensitive elements were removed from the water column by oxygenated waters, and it took time for them to build up again in the water column. Therefore, subsequent to such Major Baltic Inflows (MBIs), dissolved Mn levels and shell Mn/Ca values were strongly reduced despite summertime low-oxygen conditions. As demonstrated here, Mn/Ca data of A. islandica shells can potentially serve as a proxy for dissolved oxygen levels in the water column. To further develop this proxy, a set of additional environmental and physiological proxies such as shell Ba/Ca values and growth rate should be critically assessed and used in combination with shell Mn/Ca.

Description: Highlights: • Stable isotope values vary among species with Adelieledone polymorpha, having highest values. • Variations in trace element concentrations suggest different feeding ecology. • Antarctic incirrate octopods are likely vectors of As, Cd and Hg to their predators. • Sex influences Cd, Co, Cu, Fe, Pb and Zn concentrations. Despite the Antarctic Ocean being considered a pristine environment, elevated trace element concentrations have been reported in many marine organisms. The Antarctic Ocean is particularly vulnerable to climate change, which can also affect the bioaccumulation of trace element concentrations in biota. While Antarctic octopods are key components of the regional food webs as prey for a variety of predators (e.g., seals, fish, and seabirds), their contamination state by trace elements remains largely unknown. This study investigated the trace element concentrations in relation to the trophic ecology in Antarctic octopods. Stable isotope values (δ13C and δ15N) and trace element concentrations (Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, V, and Zn) were measured in eight different species (Adelieledone polymorpha, Pareledone aequipapillae, P. albimaculata, P. aurata, P. charcoti, P. cornuta, P. felix, and P. turqueti) sampled near Elephant Island, close to the Antarctic Peninsula. Stable isotopes of δ15N varied among species, with significant differences between A. polymorpha and P. aurata suggesting potential niche segregation. Trace element concentrations also differed among species and with sampling depth, which likely reflects their trophic ecology. The data presented in this study provides the first insight into the trace element concentrations for these endemic octopods in this vulnerable habitat and their stable isotope values

Description: Highlights • Tephrostratigraphic record from the Ionian Sea for the past 800 kyr. • 7 macro- and 19 cryptotephra layers traced to Italian and Aegean Arc sources. • Tephras provide first direct land-sea correlations in the Eastern Mediterranean region for MIS 13–9. • New insight into Middle Pleistocene activity of Santorini and Campanian volcanoes. Abstract Direct correlations between terrestrial and marine climate-proxy records are essential in order to determine potential lead/lag relationships in the response of the terrestrial and marine realms to climate forcing. In the Eastern Mediterranean region, such land-sea correlations have not yet been established beyond c. 200 ka. To explore the potential of tephra layers for Late and Middle Pleistocene land-sea correlations in the Eastern Mediterranean region, we have revisited yet unconfirmed tephra layers previously reported from Ocean Drilling Program (ODP) Site 964 (Ionian Basin) for the past c. 800 kyr in order to identify their origin and examine potential terrestrial counterparts. Using major- and trace-element glass analyses, we confirmed the presence of seven visible tephra layers with ages from 623 to 38 ka. These tephra layers represent known tephra isochrons from Italian volcanic centers (Y-5, Y-7, X-6, and V-0) and three yet unknown eruptions from Etna (623 ka), the Campanian Volcanic Zone (CVZ; 238 ka), and Pantelleria (238 ka). Because the majority of the previously reported tephra layers from ODP Site 964 were identified as clastic layers of non-volcanic origin, cryptotephra analyses were carried out for cores spanning Marine Isotope Stages (MIS) 13 to 9 (500–320 ka). This effort yielded 19 cryptotephra layers originating from Santorini volcano, the CVZ, possibly Roccamonfina volcano, and an undefined source in either the Aeolian Islands or the South Aegean Volcanic Arc. Two tephra layers are correlated with potential equivalents from terrestrial archives on the Italian and Balkan Peninsulas, including tephra isochrons SC5/A7/OH-DP-1966 (c. 493 ka; Mercure basin, Acerno basin, and Lake Ohrid) and TP09–65.95 (c. 359 ka; Tenaghi Philippon) that represent an unknown eruption of Roccamonfina and the Cape Therma 1 eruption of Santorini, respectively. Direct linking of the marine record from ODP Site 964 with the terrestrial records from Tenaghi Philippon, Lake Ohrid, and the Acerno basin via tephra tie points allowed us to circumvent shortcomings of the individual age models, and to obtain a comprehensive picture of climate variability in the greater Eastern Mediterranean region for the MIS 13–9 interval.

Description: Highlights: • Existence of well defined coccolithophore assemblages-depth zonation. • Identification of four typical depth-related coccolithophore groups. • Transport of costal coccolithophore community, trapped into an eddy, from the African coast towards Cabo Verde. • Overall shallowing of the entire coccolithophore community, with the UPZ compressed within the first 60 m. • Role of the weak NE trades and the migration of the ITCZ in the species distribution. A systematic investigation of the extant coccolithophore community around Cabo Verde archipelago was performed during the cruise MSM49 of RV Maria S. Merian, which took place in the late fall of 2015. The description of the spatial and vertical distributions of coccolithophores was based on a survey performed to the north, east and south of Cabo Verde archipelago, between the surface and 150 m water depth. The total cell densities obtained for the studied region were relatively low, reaching to a maximum of 30 × 103 cell L−1 in the upper 50 m over the southeastern slope of the Senghor seamount. Emiliania huxleyi and Gephyrocapsa oceanica were the dominant species, followed by Florisphaera profunda. The coccolithophore distribution off Cabo Verde was essentially explained by relatively warm and nutrient-depleted waters in the region during the surveyed interval, in result of the weaker NE trade winds and the northward migration of the Intertropical Convergence Zone. In these conditions, a notable zonation of coccolithophores along depth was depicted, in consequence of the inferred general well-stratified water column. Four typical depth-related groups were identified: (i) a Shallow oligotrophic (10–30 m), represented by Discosphaera tubifera and Umbellosphaera spp.; (ii) an Intermediate (40–50 m), formed by the three placolith-bearing species E. huxleyi, G. ericsonii and G. oceanica, and by Algirosphaera robusta, Helicosphaera spp., Michaelsarsia spp., Syracosphaera spp. and Umbilicosphaera spp.; (iii) a Deep (60–75 m) with F. profunda, Ophiaster spp., Oolithotus spp. and Reticulofenestra sessilis as typical members; (iv) and The Deepest (〉80 m), composed by Gladiolithus flabellatus and Syracosphaera lamina. In addition, high abundances of G. oceanica related with the Eddy station were attributed to the transport and thriving of the coastal coccolithophore community, dominated by this species, from the African coast towards Cabo Verde

Description: Highlights • Inherent & added tracers were tested for CO2 leakage attribution & quantification. • Additionally, CO2 leakage was quantified directly by the inverted funnel-technique. • All tracers except 18O were capable of attributing the CO2 source. • In total, ∼43 % of total injected CO2 leaked across the seabed. To inform cost-effective monitoring of offshore geological storage of carbon dioxide (CO2), a unique field experiment, designed to simulate leakage of CO2 from a sub-seafloor storage reservoir, was carried out in the central North Sea. A total of 675 kg of CO2 were released into the shallow sediments (∼3 m below seafloor) for 11 days at flow rates between 6 and 143 kg d-1. A set of natural, inherent tracers (13C, 18O) of injected CO2 and added, non-toxic tracer gases (octafluoropropane, sulfur hexafluoride, krypton, methane) were used to test their applicability for CO2 leakage attribution and quantification in the marine environment. All tracers except 18O were capable of attributing the CO2 source. Tracer analyses indicate that CO2 dissolution in sediment pore waters ranged from 35 % at the lowest injection rate to 41% at the highest injection rate. Direct measurements of gas released from the sediment into the water column suggest that 22 % to 48 % of the injected CO2 exited the seafloor at, respectively, the lowest and the highest injection rate. The remainder of injected CO2 accumulated in gas pockets in the sediment. The methodologies can be used to rapidly confirm the source of leaking CO2 once seabed samples are retrieved.

Description: Highlights • Si was measured with micrometer resolution in mantle wedge serpentinites. • Serpentine Si varies depending on w/r ratios and Si of interacting fluids. • Si in veins formed under high w/r ratios mirror that of subducted sediments. • Across-forearc changes in Si fingerprint prograde slab dehydration reactions. • Si isotopes provide a new tool for tracing slab dehydration processes. Abstract The Mariana forearc is a unique location for exploring the role serpentinization plays in the marine Si cycle by means of Si stable isotope variations. Here, active mud volcanism transports deep, serpentinized mantle wedge material to the surface and thus offers a natural window to slab dehydration processes in dependence of changing temperature and pressure with depth. Si isotopes were measured in situ by femtosecond laser ablation MC-ICPMS in serpentine within ultramafic clasts from three mud volcanoes (Yinazao, Fantangisña, and Asùt Tesoru) sampled during International Ocean Discovery Program Expedition 366. To corroborate the results, serpentinization of olivine was studied in batch experiments. The Si isotope ratios show large variations between the mud volcanoes and between individual serpentine generations within a given mud volcano. Serpentine that formed early under low water/rock ratios exhibits Si of −0.41 ± 0.04‰ (1SD) similar to unaltered olivine which agrees well with experimental findings predicting no significant isotope fractionation during early serpentinization. In contrast, late serpentine veins formed under higher water/rock ratios span a wide range of Si isotope ratios that differ significantly between the individual mud volcanoes. With increasing distance to the trench, Si of late veins are −0.10 ± 0.07‰, −1.94 ± 0.13‰, and −0.80 ± 0.22‰ and −0.93 ± 0.21‰. These Si values are interpreted to record the isotopic composition of the fluid source, namely subducted biogenic silica and pore fluids, clays, and altered oceanic crust that dehydrate as consequence of rising pressure and temperature with depth. We show that Si isotopes of mantle wedge serpentinites can be used as a reliable new proxy for slab dehydration processes. They may be used in paleo-forearc systems to unravel oceanic sediment and silica biomineralization evolution through geological time.

Description: Highlights • Marine CSEM data was collected in the Danube Paleo-delta, Black Sea for gas hydrate targets investigation. • The receivers and the novel transmitter “Sputnik” developed at GEOMAR (Helmholtz Centre for Ocean Research Kiel) were used. • Inversions in terms of rotational invariants are conducted. • Two potential gas hydrate layers are derived. • Gas hydrate saturation is estimated using Archie's Law. Abstract The Black Sea is known to have extensive direct and indirect indicators of methane hydrates. Since the resistivity of the seafloor increases significantly in the presence of gas hydrates or free gas, marine controlled-source electromagnetics (CSEM) is a suitable method for the investigation of hydrates. We have collected CSEM data in a channel-levee system of the Danube paleo-delta (Bulgarian sector) at water depths of about 1500 m. The working area is within the gas hydrates stability zone and seismics suggests the presence of gas hydrates. The CSEM data were acquired with stationary receivers and a novel mobile, dual polarization transmitter system, and interpreted in terms of rotational invariants by means of 1-D inversions at common midpoints (CMP) to generate pseudo 2D resistivity sections. The inversion results reveal two resistive layers at shallow depths of 60–120 mbsf and greater depths of 270–400 mbsf. A comparison with seismics shows a good correlation of the shallow layer with high amplitude reflections and a velocity anomaly. The deeper layer can be tied to the current bottom simulating reflector (BSR). The comparison to a second CSEM experiment, which was conducted by the BGR (Federal Institute for Geosciences and Natural Resources, Germany) shows a good agreement of the derived sections down to a depth of about 350 m. Based on salinity and porosity models derived from boreholes in the Black Sea, we apply Archie's law to estimate potential gas hydrate saturations of up to 23% for the shallow resistor and up to 7% for the deeper layer. Differences are evident at depths greater than 450 m, where we see a conductive layer not evident in the BGR section. This deeper conductor could be evidence for increasing salinities of pore fluids at greater depths, which were previously found in DSDP drilling cores.