ALBERT

Description: Highlights • Internal diffusion often controls the releases of flame retardants from microplastics. • Fick's law can describe the releases of additive flame retardants from microplastics. • Effects of temperature, plastic matrix, and particle size can be predicted by models. • Weathering of plastic matrix can greatly accelerate the releases of flame retardants. • Low fluxes of flame retardants released from microplastics pose no risk to ecosystem. The widely occurring debris of plastic materials, particularly microplastics, can be an important source of flame retardants, which are one of the main groups of chemicals added in the production of plastics from polymers. This review provides an overview on the use of flame retardants in plastic manufacturing, the kinetics of their releases from microplastics, the factors affecting their releases, and the potential environmental and ecosystem risk of the released flame retardants. The releases of flame retardants from microplastics typically involve three major steps: internal diffusion, mass transfer across the plastic-medium boundary layer, and diffusion in the environmental medium, while the overall mass transfer rate is commonly controlled by diffusion within the plastic matrix. The overall release rates of additive flame retardants from microplastics, which are dependent on the particle's geometry, can often be described by the Fick's Law. The physicochemical properties of flame retardant and plastic matrix, and ambient temperature all affect the release rate, which can be predicted with empirical and semi-empirical models. Weathering of microplastics, which reduces their particle sizes and likely disrupts their polymeric structures, can greatly accelerate the releases of flame retardants. Flame retardants could also be released directly from the microplastics ingested by aquatic organisms and seabirds, with physical and chemical digestion in the bodies significantly enhancing their release rates. Limited by the extremely slow diffusion in plastic matrices, the fluxes of flame retardants released from microplastics are very low, and are unlikely to pose significant risk to the ecosystem in general. More research is needed to characterize the mechanical, chemical, and biological processes that degrade microplastics and accelerate the releases of flame retardants and to model their release kinetics from microplastics, while efforts should also be made to develop environmentally benign flame retardants to ultimately minimize their risk to the environment and ecosystem.

Description: Ongoing discoveries of terrestrial exoplanets and the desire to determine their habitability have created an increasing demand for studies of a wide range of climatic regimes and atmospheric circulations. These studies have, in turn, challenged our understanding of our own planet’s atmospheric dynamics and provided new frameworks with which we can further our understanding of planetary atmospheres. In this work, we use an idealized moist general circulation model in aquaplanet configuration to study the atmospheric circulation of terrestrial planets with high obliquities. With seasonally varying insolation forcing and a shallow slab ocean as a lower boundary, we emphasize seasonal phenomena that might not be captured in simulations with annual mean forcing and that might involve nonlinear behaviors. By progressively increasing obliquity, we explore the response of the large-scale atmospheric circulation to more extreme seasonal cycles and a reversed annual mean equator-to-pole insolation distribution, and its impact on the energy and water cycles. We show that for high obliquities, the large-scale atmospheric circulation and the meridional energy transport are dominated by seasonally reversing broad cross-equatorial Hadley cells that transport energy from the summer to the winter hemisphere and significantly mitigate temperature extremes. These overturning cells also play a major role in shaping the planet’s hydrological cycle, with the associated ascending branches and precipitation convergence zones becoming progressively broader and more poleward shifted into the summer hemisphere with higher obliquities. While not embedded within the Hadley cell ascending branches, the hot summer poles of high obliquity planets experience nonnegligible precipitation during and at the end of the warm season: during the summer, lower-level moist static energy maxima at the summer poles force locally enhanced convective activity. As temperatures rapidly drop at the end of the summer and convective activity decreases, the water-holding capacity of the atmosphere decreases and water vapor stored in the atmospheric column rapidly condenses out, extending the duration of the summer pole rainy season into the corresponding autumn. Our study reveals novel understanding of how atmospheric dynamics might influence a planet’s overall climate and its variability.

Description: The analysis of three extreme African dust outbreaks over the Iberian Peninsula (IP) shows that a double Rossby wave breaking (RWB) process in the polar jet (PJ) creates the conditions for dust storm formation over subtropical deserts in North Africa and the restructuring of upper-level air flows critical for the dust transport poleward after ablation. Two consecutive anticyclonic RWBs initiate over the IP and the adjacent Atlantic, the first commencing 10 days before dust reaches the IP and the second three to five days later. The first RWB becomes quasi-stationary over the eastern Mediterranean when the second RWB develops. In turn, the first RWB blocks downstream propagation of the second, which is amplified by energy reflection poleward from the first break causing vortex intensification and equatorward propagation over the Atlas as well as a strengthening and coupling of the subtropical jet (STJ) to circulations in the ITCZ. Zonal flows are blocked and sustained low-level northeasterlies/easterlies are induced across northwest Africa. The three events present substantial differences in the location and geometry of key upper- and low-level subsynoptic features that organize the dust storms over the Sahara following the second break. Dust lifted by either the cold outflow from convective downdrafts or by orographic gravity waves interacts with terrain-induced and larger scale circulations and is transported to the IP. The location of the cyclonic large scale signal from the second RWB to the west or over the Atlas and the blocking of zonal flows are key for the poleward dust transport.

Description: Based on the numerical weather prediction model COSMO of Germany's national meteorological service (Deutscher Wetterdienst, DWD), regional reanalysis datasets have been developed with grid spacing of up to 2 km. This development started as a fundamental research activity within the Hans-Ertel-Centre for Weather Research (HErZ) at the University of Bonn and the University of Cologne. Today, COSMO reanalyses are an established product of the DWD and have been widely used in applications on European and national German level. Successful applications of COSMO reanalyses include renewable energy assessments as well as meteorological risk estimates. The COSMO reanalysis datasets are now publicly available and provide spatio-temporal consistent data of atmospheric parameters covering both near-surface conditions and vertical profiles. This article reviews the status of the COSMO reanalyses, including evaluation results and applications. In many studies, evaluation of the COSMO reanalyses point to an overall good quality and often an added value compared to different contemporary global reanalysis datasets. We further outline current plans for the further development and application of regional reanalyses in the HErZ research group Cologne/Bonn in collaboration with the DWD.

Description: The effective radiative forcing, which includes the instantaneous forcing plus adjustments from the atmosphere and surface, has emerged as the key metric of evaluating human and natural influence on the climate. We evaluate effective radiative forcing and adjustments in 17 contemporary climate models that are participating in the Coupled Model Intercomparison Project (CMIP6) and have contributed to the Radiative Forcing Model Intercomparison Project (RFMIP). Present-day (2014) global-mean anthropogenic forcing relative to pre-industrial (1850) levels from climate models stands at 2.00 (±0.23) W m−2, comprised of 1.81 (±0.09) W m−2 from CO2, 1.08 (± 0.21) W m−2 from other well-mixed greenhouse gases, −1.01 (± 0.23) W m−2 from aerosols and −0.09 (±0.13) W m−2 from land use change. Quoted uncertainties are 1 standard deviation across model best estimates, and 90 % confidence in the reported forcings, due to internal variability, is typically within 0.1 W m−2. The majority of the remaining 0.21 W m−2 is likely to be from ozone. In most cases, the largest contributors to the spread in effective radiative forcing (ERF) is from the instantaneous radiative forcing (IRF) and from cloud responses, particularly aerosol–cloud interactions to aerosol forcing. As determined in previous studies, cancellation of tropospheric and surface adjustments means that the stratospherically adjusted radiative forcing is approximately equal to ERF for greenhouse gas forcing but not for aerosols, and consequentially, not for the anthropogenic total. The spread of aerosol forcing ranges from −0.63 to −1.37 W m−2, exhibiting a less negative mean and narrower range compared to 10 CMIP5 models. The spread in 4×CO2 forcing has also narrowed in CMIP6 compared to 13 CMIP5 models. Aerosol forcing is uncorrelated with climate sensitivity. Therefore, there is no evidence to suggest that the increasing spread in climate sensitivity in CMIP6 models, particularly related to high-sensitivity models, is a consequence of a stronger negative present-day aerosol forcing and little evidence that modelling groups are systematically tuning climate sensitivity or aerosol forcing to recreate observed historical warming.

Description: We present the result of the third Marine Ice Sheet Intercomparison project, MISMIP+. MISMIP+ is intended to be a test of ice flow models which include fast sliding marine ice streams and floating ice shelves and in particular a treatment of viscous stress that is sufficient for buttressing, where upstream ice flow is restrained by a downstream ice shelf. A set of idealized experiments test the models in circumstances where buttressing contributes to a stable steady state, and where a reduction in that buttressing causes ice stream acceleration, thinning, and grounding line retreat. We find that the most important distinction between models in this particular type of simulation is in the treatment of sliding at the bed, with other distinctions – notably the difference between the simpler and more complete treatments of englacial stress, but also the differences between numerical methods – taking a secondary role.

Description: Varved lake sediments provide long climatic records with high temporal resolution and low associated age uncertainty. Robust and detailed comparison of well-dated and annually laminated sediment records is crucial for reconstructing abrupt and regionally time-transgressive changes as well as validation of spatial and temporal trajectories of past climatic changes. The VARved sediments DAtabase (VARDA) presented here is the first data compilation for varve chronologies and associated palaeoclimatic proxy records. The current version 1.0 allows detailed comparison of published varve records from 95 lakes. VARDA is freely accessible and was created to assess outputs from climate models with high-resolution terrestrial palaeoclimatic proxies. VARDA additionally provides a technical environment that enables to explore the database of varved lake sediments using a connected data-model and can generate a state-of-the-art graphic representation of multi-site comparison. This allows to reassess existing chronologies and tephra events to synchronize and compare even distant varved lake records. Furthermore, the present version of VARDA permits to explore varve thickness data. In this paper, we report in detail on the data mining and compilation strategies for the identification of varved lakes and assimilation of high-resolution chronologies as well as the technical infrastructure of the database. Additional paleoclimate proxy data will be provided in forthcoming updates. The VARDA graph-database and user interface can be accessed online at https://varve.gfz-potsdam.de, all datasets of version 1.0 are available at http://doi.org/10.5880/GFZ.4.3.2019.003 (Ramisch et al., 2019).

Description: Various observational estimates indicate growing mass loss at Antarctica's margins but also heavier precipitation across the continent. In the future, heavier precipitation fallen on Antarctica will counteract any stronger iceberg discharge and increased basal melting of floating ice shelves driven by a warming ocean. Here, we use from nine CMIP5 models future projections, ranging from strong mitigation efforts to business-as-usual, to run an ensemble of ice-sheet simulations. We test, how the precipitation boundary condition determines Antarctica's sea-level contribution. The spatial and temporal varying climate forcings drive ice-sheet simulations. Hence, our ensemble inherits all spatial and temporal climate patterns, which is in contrast to a spatial mean forcing. Regardless of the applied boundary condition and forcing, some areas will lose ice in the future, such as the glaciers from the West Antarctic Ice Sheet draining into the Amundsen Sea. In general the simulated ice-sheet thickness grows in a broad marginal strip, where incoming storms deliver topographically controlled precipitation. This strip shows the largest ice thickness differences between the applied precipitation boundary conditions too. On average Antarctica's ice mass shrinks for all future scenarios if the precipitation is scaled by the spatial temperature anomalies coming from the CMIP5 models. In this approach, we use the relative precipitation increment per degree warming as invariant scaling constant. In contrast, Antarctica gains mass in our simulations if we apply the simulated precipitation anomalies of the CMIP5 models directly. Here, the scaling factors show a distinct spatial pattern across Antarctica. Furthermore, the diagnosed mean scaling across all considered climate forcings is larger than the values deduced from ice cores. In general, the scaling is higher across the East Antarctic Ice Sheet, lower across the West Antarctic Ice Sheet, and lowest around the Siple Coast. The latter is located on the east side of the Ross Ice Shelf.

Description: A finely laminated lake sediment record with a basal age of 11,619 ± 603 years BP was retrieved from Lake Chatyr Kol (Kyrgyz Republic). Microfacies analysis reveals the presence of seasonal laminae (varves) from the sediment basis to ~ 360 ± 40 years BP. The Chatvd19 floating varve chronology covers the time span from 360 ± 40 years BP to the base and relies on replicate varve counts on overlapping petrographic thin sections with an uncertainty of ± 5 %. The uppermost non-varved interval was chronologically constrained by 210Pb and 137Cs γ-spectrometry and interpolation based on varve thickness measurements of adjacent varved intervals with an assumed uncertainty of 10 %. Six varve types were distinguished, are described in detail and show a changing predominance of clastic-organic, clastic-calcitic or -aragonitic, calcitic-clastic, organic-clastic and clastic-diatom varves throughout the Holocene. Variations in varve thickness and the number and composition of seasonal sublayers are attributed to 1) changes in the amount of summer or winter/spring precipitation affecting local runoff and erosion and/or to 2) evaporative conditions during summer. Radiocarbon dating of bulk organic matter, daphnia remains, aquatic plant remains and Ruppia maritima seeds reveal reservoir ages with a clear decreasing trend up core from ~ 6,150 years in the early Holocene, to ~ 3,000 years in the mid-Holocene, to ~ 1,000 years and less in the late Holocene and modern times. In contrast, two radiocarbon dates from terrestrial plant remains are in good agreement with the varve-based chronology.

Description: Aqueous sorption processes play an important role in, for example, pollutant binding to natural nanoparticles, colloid stability, separation and enrichment of components and remediation processes. In this article, which is a tribute to Hans Lyklema, models of localized (ad)sorption of molecules and ions from aqueous solution on homogeneous and heterogeneous nanoparticles are presented. The discussed models range from ideal monocomponent sorption on homogeneous (Langmuir) and heterogeneous sites, to multicomponent ideal sorption on homogeneous and heterogeneous sites, multicomponent multisite ion complexation with charge distribution (CD-MUSIC) and non-ideal competitive adsorption on heterogeneous sites (NICA). Attention is also paid to lateral interaction, site-induced aggregation, binding stoichiometry and multilayer formation. Electrical double layer models are discussed in relation to ion binding on impermeable and permeable nanoparticles. Insight in models that can describe sorption of molecules and ions on nanoparticles leads to awareness of the limitations of using simple models for complex systems and is needed for the selection and application of an appropriate model for a given system. This is relevant for all practical sorption processes and for a better understanding of the role of natural nanoparticles in the binding of nutrients and pollutants.

Description: These are the first animals to pass mutations found outside sex cells

Description: Clastic dominant-type massive sulfide deposits are well preserved in Upper Devonian carbonaceous mudstones in the Macmillan Pass district (Yukon, Canada). The Macmillan Pass deposits have been considered to be type examples of sedimentary exhalative Zn-Pb mineralization, whereby sulfides precipitated when hydrothermal fluids were vented into a euxinic (H2S-bearing) water column. We propose a new mineralization model, documenting the mineralogical evolution of layered mineralization. We show that textures previously interpreted to form via depositional processes actually formed by subseafloor replacement of diagenetic barite. Mineral assemblages associated with barite dissolution in the layered mineralization include (1) barium carbonate phases (witherite, barytocalcite, and norsethite), which are intergrown with Zn-Pb sulfides and represent localized Ba mass transfer, and (2) barium feldspar (celsian, hyalophane) that is abundant in the mudstones surrounding the layered mineralization. The barium feldspar formed following transport of Ba in low-sulfate fluids on the margins of the subseafloor replacement system. This resulted in whole-rock Ba enrichments (up to 5 wt %) in mudstones 15 m below and above the layered mineralization. High Ba in these surrounding mudstones is coupled with decreasing K/Al ratios, indicative of secondary illite and kaolinite. The source(s) of fluids related to the diagenetic (barite, barytocalcite) and hydrothermal (ankerite) assemblages can be constrained using Sr isotopes. Whereas highly radiogenic 87Sr/86Sr values (〉0.714) in ankerite correspond with host-rock alteration within the vent complex, the overlying barite and barytocalcite preserve lower 87Sr/86Sr values (〈0.714), providing evidence of mixing between a radiogenic fluid (likely a formation water) and Late Devonian seawater. The complex mineralogy and paragenesis contained within the layered mineralization are linked to a protracted history of diagenetic and hydrothermal fluid events, all of which took place in and peripheral to a subseafloor replacement hydrothermal system.

Description: The representation of tropical precipitation is evaluated across three generations of models participating in phases 3, 5, and 6 of the Coupled Model Intercomparison Project (CMIP). Compared to state-of-the-art observations, improvements in tropical precipitation in the CMIP6 models are identified for some metrics, but we find no general improvement in tropical precipitation on different temporal and spatial scales. Our results indicate overall little changes across the CMIP phases for the summer monsoons, the double-ITCZ bias, and the diurnal cycle of tropical precipitation. We find a reduced amount of drizzle events in CMIP6, but tropical precipitation occurs still too frequently. Continuous improvements across the CMIP phases are identified for the number of consecutive dry days, for the representation of modes of variability, namely, the Madden–Julian oscillation and El Niño–Southern Oscillation, and for the trends in dry months in the twentieth century. The observed positive trend in extreme wet months is, however, not captured by any of the CMIP phases, which simulate negative trends for extremely wet months in the twentieth century. The regional biases are larger than a climate change signal one hopes to use the models to identify. Given the pace of climate change as compared to the pace of model improvements to simulate tropical precipitation, we question the past strategy of the development of the present class of global climate models as the mainstay of the scientific response to climate change. We suggest the exploration of alternative approaches such as high-resolution storm-resolving models that can offer better prospects to inform us about how tropical precipitation might change with anthropogenic warming.

Description: The total cultivable microbiota of the ice-stored European sea bass (Dicentrarchus labrax), the most important commercial fish species of the Mediterranean aquaculture, was determined using 16S rRNA gene sequence analysis. High Resolution Melting (HRM) curve profiles and sequencing analysis (V3–V4 region of the 16S rRNA gene) were used respectively for the differentiation and identification of the collected isolates from six time intervals (day 0, 4, 8, 12, 14 and 16) while fish were stored in ice. HRM analysis differentiated the unknown microbiota in ten groups (208 isolates) and in two single isolates based on their HRM curve profiles. The isolates with HRM profiles which were 〉91% similar within each group were found to belong to the same species using sequencing analysis. Thus, the ten groups consist of representatives of Psychrobacter glacincola, Ps. alimentarius, Ps. cryohalolentis, Ps. maritimus, Ps. fozii, Pseudomonas sp., Paeniglutamicibacter sp., Carnobacterium sp., Leucobacter aridicolis and Bacillus thuringiensis. Based on this approach, Ps. cryohalolentis was found to be the most dominant phylotype at the beginning of fish shelf-life compared to other species. The abundance of this bacterium decreased throughout storage, while Ps. glacincola increased and dominated at the time of the sensory minimum acceptability (day 14) and rejection (day 16). To conclude, HRM could be used for the rapid determination of sea bass microbiota, using the representatives of each group as reference bacterial strains, in order for scientists to solve rapidly stakeholders problems related with microbial quality or safety of fish.

Description: Controlled-source electromagnetics (CSEM) can be used to image subsurface resistivity and add value in petroleum exploration. However, the application of CSEM methods can be particularly challenging in mature oil and gas fields, where the presence of steel casings and complex seabed infrastructure may influence electromagnetic (EM) fields. The effect of this metal infrastructure can be modeled using the method of moments (MoM), which has previously been demonstrated to be effective in simple situations. We have now developed a methodology for modeling the EM response of complex pipeline geometry using MoM, and we validate our approach numerically and experimentally; the difference between finite-element and MoM modeling is less than 3%, whereas the difference between experimental data and MoM results is less than 30%. We further develop a fast and efficient approach to model the EM response of horizontal pipeline infrastructure. First, we create individual pipe sections of custom shape; when assembled, these sections are used to construct the entire pipeline system. We then identify “precise” and “approximate” zones based on how accurately we need to perform the calculations. We find that the electric field values in the approximate zone can be calculated accurately and quickly using previously saved table values, and therefore achieve a considerable reduction in computational requirements. Finally, we apply our methodology to a real situation of a 60 km horizontal seabed pipeline and find that the electric field distortion can be calculated rapidly and efficiently with our custom-built algorithm.

Description: Ice flow models of the Antarctic ice sheet are commonly used to simulate its future evolution in response to different climate scenarios and inform on the mass loss that would contribute to future sea level rise. However, there is currently no consensus on estimated the future mass balance of the ice sheet, primarily because of differences in the representation of physical processes and the forcings employed. This study presents results from 18 simulations from 15 international groups focusing on the evolution of the Antarctic ice sheet during the period 2015–2100, forced with different scenarios from the Coupled Model Intercomparison Project Phase 5 (CMIP5) representative of the spread in climate model results. The contribution of the Antarctic ice sheet in response to increased warming during this period varies between −7.8 and 30.0 cm of Sea Level Equivalent (SLE). The evolution of the West Antarctic Ice Sheet varies widely among models, with an overall mass loss up to 21.0 cm SLE in response to changes in oceanic conditions. East Antarctica mass change varies between −6.5 and 16.5 cm SLE, with a significant increase in surface mass balance outweighing the increased ice discharge under most RCP 8.5 scenario forcings. The inclusion of ice shelf collapse, here assumed to be caused by large amounts of liquid water ponding at the surface of ice shelves, yields an additional mass loss of 8 mm compared to simulations without ice shelf collapse. The largest sources of uncertainty come from the ocean-induced melt rates, the calibration of these melt rates based on oceanic conditions taken outside of ice shelf cavities and the ice sheet dynamic response to these oceanic changes. Results under RCP 2.6 scenario based on two CMIP5 AOGCMs show an overall mass loss of 10 mm SLE compared to simulations done under present-day conditions, with limited mass gain in East Antarctica.

Description: Quinoa (Chenopodium quinoa Willd.), an herb belonging to the amaranth family, is rich in minerals, amino acids, vitamins, proteins, and flavonoids. Its grain, compared with other major grains, has unique nutritional value with tremendous applications. This study used four independently bred high-generation lines (seed colors) of quinoa as materials to further understand the metabolic differences in the filling periods of quinoa varieties. Additionally, the non-targeted metabolome of quinoa seeds 35 and 42 days after flowering, respectively, were studied via liquid chromatography-mass spectrometry. The two filling periods of yellow, white, black, and red quinoa grains resulted in significant differences in the metabolites, particularly in L-methionine, S-adenosyl-L-homocysteine, S-adenosyl-L-methionine, pyruvate, fumarate, and oxaloacetate. Soluble sugar, amino acid, and fatty acid contents in quinoa increased after 42 days of flowering. There were metabolic differences between the sugar phosphates (L-fucose, D-mannose-6-phosphate, xylulose-5-phosphate, sedoheptulose-7-phosphate), amino acid (alanine), and organic compounds (kynurenate, tryptamine, serotonin, bilirubin) among the four quinoa varieties. The relative difference in the metabolites was largest when the yellow quinoa grain was compared with the other quinoa varieties and smallest when the red and black varieties were compare. The results of this study provide a basis for the reproduction and identification of new quinoa varieties, as well as for screening potential quality control target genes by combining genomics and transcriptomics.

Description: We processed three quinoa ecotypes as they are commonly consumed in a daily diet. For the treatments, quinoa seeds were washed, cooked, and/or germinated. Following treated, we used 1H NMR-based metabolomic profiling to explore differences between the ecotypes. Then, for a non-targeted and targeted food fingerprint analysis of samples, we performed multivariable data analyses, including principal component analysis (PCA), orthogonal partial least squares discriminant analysis (OPLS-DA), and hierarchical cluster analysis. From our study, we were able to discriminate each quinoa ecotype regardless of treatment based on its metabolomic profiling. Additionally, we were able to identify 30 metabolites that were useful to determine the effect of each treatment on nutritional composition. Germination increased the content of most metabolites irrespective of ecotype. In general, ecotype CQE_03 was different from ecotypes CQE_01 and CQE_02. Our phytochemical analysis revealed the effects of washing, cooking, and/or germination, particularly on saponins content.

Description: We evaluated passage of Osmerus mordax (Rainbow Smelt), Salvelinus fontinalis (Brook Trout), and Alosa pseudoharengus (Alewife) at 4 fishways on Prince Edward Island, Canada. We implanted fish with passive integrated transponder (PIT) tags and recorded their movements using stationary PIT antennas. Passage at different fishway types was highly variable. Nature-like fishways passed over 96% of Brook Trout and a maximum of 41.8% of Rainbow Smelt. The latter percentage is the highest yet reported in the literature for Rainbow Smelt. Pool-and-weir fishways passed nearly 100% of Brook Trout, 13.2% of Rainbow Smelt, and only 5.6% of Alewife. After passing a fishway, upstream residency was highly variable both among species as well as among individuals within species. Rainbow Smelt were observed spawning within nature-like fishways, suggesting that this type of fishway may also provide spawning habitat. Results highlight the challenge of passing non-salmonid species and indicate nature-like fishways are more appropriate than technical designs for passing Rainbow Smelt.

Description: Nur etwa 20 % des Meeresbodens sind bislang mit Fächerecholoten kartiert worden. Größere zusammenhängende Flächen werden selten systematisch und hochauflösend kartiert. Stattdessen gibt es den Ansatz, dass Forschungsschiffe Bathymetriedaten auf Transitstrecken aufnehmen. Im Pilotprojekt »Unterwegs«-Forschungsdaten der DAM – Deutsche Allianz Meeresforschung tragen deutsche Forschungsschiffe dazu bei, weitere Teilstücke des Meeresbodens zu kartieren, um Datenlücken zu schließen. Die Bathymetriedaten werden im Datenarchiv PANGAEA veröffentlicht und von dort in das Portal Deutsche Meeresforschung integriert.

Description: Objectives of the Cruise The objective of the cruise was to locate dumped chemical and conventional munition in dumping grounds around Helgoland in the North Sea. More specifically the objectives were: ▪ Mapping dumping grounds with high resolution multibeam (MBES) and identify munition locations on the seafloor ▪ Evaluating the MBES RESON SeaBat T50 Extended Range for enhanced munition detection ▪ Mapping munition locations with high resolution SBP to detect buried munition an create 3D datasets ▪ Taking water samples for TNT and chemical warfare (CW) analyses

Description: The objective of the cruise was to locate dumped chemical and conventional munition in dumping grounds around Helgoland in the North Sea. More specifically the objectives were: ▪ Mapping dumping grounds with high resolution multibeam (MBES) and identify munition locations on the seafloor ▪ Evaluating the MBES RESON SeaBat T50 Extended Range for enhanced munition detection ▪ Mapping dumping grounds with sediment echosounder (SES) to learn the sedimentary and geologic background of the areas ▪ Mapping munition locations with high resolution SES to detect buried munition an create 3D dataset ▪ Taking water samples for TNT analyses

Description: (GPF20-3_088), 10.10. - 10.11.2020, Emden - Emden

Description: The decarbonisation of industry is a bottleneck for EU's 2050 target of climate neutrality. Replacing fossil fuels with low-carbon electricity is at the core of this challenge; however, the aggregate electrification potential and resulting system-wide CO2 reductions for diverse industrial processes are unknown. Here, we present the results from a comprehensive bottom-up analysis of the energy use in eleven industrial sectors (accounting for 92% of Europe's industry CO2 emissions), and estimate the technological potential for industry electrification in three stages. 78% of the energy demand is electrifiable with technologies that are already established, while 99% electrification can be achieved with the addition of technologies currently under development. Such a deep electrification reduces CO2 emissions already based on the carbon intensity of today's electricity (~300 gCO2/kWhel). With an increasing decarbonisation of the power sector (IEA: 12 gCO2/kWhel in 2050), electrification could cut CO2 emissions by 78%, and almost entirely abate the energy-related CO2 emissions, reducing the industry bottleneck to only residual process emissions. Despite its decarbonisation potential, the extent to which direct electrification will be deployed in industry remains uncertain and depends on the relative cost of electric technologies compared to other low-carbon options.

Description: We emphasize the importance of marine silicate weathering (MSiW) reactions in anoxic sediment as fundamental in generating alkalinity and cations needed for carbonate precipitation and preservation along continental margins. We use a model that couples thermodynamics with aqueous geochemistry to show that the CO2 released during methanogenesis results in a drop in pH to 6.0; unless these protons are buffered by MSiW, carbonate minerals will dissolve. We present data from two regions: the India passive margin and the active subduction zone off Japan, where ash and/or rivers supply the reactive silicate phase, as reflected in strontium isotope data. Offshore India and Korea, alteration of continent-derived silicates results in pore water enriched in radiogenic 87Sr, with 87Sr/86Sr ratios as high as 0.7095 and 0.7104, respectively. Off Japan, strontium in pore water influenced by ash alteration is depleted in 87Sr, with 87Sr/86Sr as low as 0.7065. Carbonate minerals formed by alkalinity and cations generated through MSiW carry these strontium isotopic signals, and are typically dolomite, siderite, and Fe-rich calcite. These contrast with the aragonite and high-magnesium calcite that form during anaerobic oxidation of methane and incorporate the coeval seawater 87Sr/86Sr signal. We show that MSiW is necessary for authigenic carbonate formation and preservation along continental margins, which remove carbon from Earth's surface at rates previously estimated to be at least 1012 mol yr−1. In addition, these authigenic carbonates are of relevance to studies of the deep biosphere, fluid flow, seismogenesis, slope stability, and reservoir characteristics.

Description: Highlights • Cadomian continental arc crust of NE Iran was built during ∼15 Myr of magmatism. • Magmatic flare-up in Iran Cadomia occurred over ∼45 Myr; 570 to 525 Ma. • Geochemical differentiation in “hot zones” built the stratified continental crust of Iran. Abstract The generation and differentiation of continental crust by arc magmatism is strongly influenced by episodes of high magmatic flux (“flare-ups”). Magmatic flare-ups encourage the development of deep crustal hot zones where magmatic differentiation and density stratification combine to form the upper felsic and lower mafic continental crust. Such processes, which are responsible for the construction of continental arc crust, are prolonged events, which build a ∼30-40 km arc crust over tens of million years (∼100 Myr). New zircon U-Pb data reveal that the construction of Cadomian crust from NE Iran occurred over ∼15 ± 0.3 Myr. However, compiled zircon U-Pb ages reveal a prolonged magmatic flare-up of ∼45 Myr; ∼570 to 525 Ma. Basement outcrops in NE Iran expose lower- and upper crust that show how magmatic-geochemical differentiation occurred deep beneath a Cadomian continental arc in a crustal hot zone. Isotopic data for igneous rocks produced during this 45 Myr episode reveal interactions between mantle-derived melts and old continental crust. Synthesis of new and published data indicates that this type of interaction is common during periods of high magmatic fluxes. Our results indicate that differentiation of mafic melts in the lower crust during prolonged magmatic flare-ups plays a key role in building a stratified continental crust.

Description: Highlights • Total amount of generated biogenic methane is estimated at ~3100 Gt. • Total amount of generated thermogenic methane is estimated at ~1,560 Gt. • The Maykop formation is partially productive in the central basin and not yet fully productive towards the basin peripherals. A new numerical model reconstructing the depositional history (98–0 Ma) of the Western Black Sea sub-basin is presented. The model accounts for changing boundary conditions (i.e. water depth, bottom water temperature, heat flow evolution over time) and estimates the rates and total amounts of the in-situ biogenic methane generation and thermally-driven organic matter maturation in the source rocks. The overall thermogenic and biogenic gas generation predicted by the model is estimated at ~1560 Gt and ~3100 Gt, respectively.

Description: The reaction between ozone and iodide at the sea surface is now known to be an important part of atmospheric ozone cycling, causing ozone deposition and the release of ozone-depleting reactive iodine to the atmosphere. The importance of this reaction is reflected by its inclusion in chemical transport models (CTMs). Such models depend on accurate sea surface iodide fields, but measurements are spatially and temporally limited. Hence, the ability to predict current and future sea surface iodide fields, i.e. sea surface iodide concentration on a narrow global grid, requires the development of process-based models. These models require a thorough understanding of the key processes that control sea surface iodide. The aim of this study was to explore if there are common features of iodate-to-iodide reduction amongst diverse marine phytoplankton in order to develop models that focus on sea surface iodine and iodine release to the troposphere. In order to achieve this, rates and patterns of changes in inorganic iodine speciation were determined in 10 phytoplankton cultures grown at ambient iodate concentrations. Where possible these data were analysed alongside results from previous studies. Iodate loss and some iodide production were observed in all cultures studied, confirming that this is a widespread feature amongst marine phytoplankton. We found no significant difference in log-phase, cell-normalised iodide production rates between key phytoplankton groups (diatoms, prymnesiophytes including coccolithophores and phaeocystales), suggesting that a phytoplankton functional type (PFT) approach would not be appropriate for building an ocean iodine cycling model. Iodate loss was greater than iodide formation in the majority of the cultures studied, indicating the presence of an as-yet-unidentified “missing iodine” fraction. Iodide yield at the end of the experiment was significantly greater in cultures that had reached a later senescence stage. This suggests that models should incorporate a lag between peak phytoplankton biomass and maximum iodide production and that cell mortality terms in biogeochemical models could be used to parameterise iodide production.

Description: The clumped isotope (Δ47) proxy is a promising geochemical tool to reconstruct past ocean temperatures far back in time and in unknown settings, due to its unique thermodynamic basis that renders it independent from other environmental factors like seawater composition. Although previously hampered by large sample-size requirements, recent methodological advances have made the paleoceanographic application of Δ47 on small (〈5 mg) foraminifer samples possible. Previous studies show a reasonable match between Δ47 calibrations based on synthetic carbonate and various species of planktonic foraminifers. However, studies performed before recent methodological advances were based on relatively few species and data treatment that is now outdated. To overcome these limitations and elucidate species-specific effects, we analyzed 14 species of planktonic foraminifers in sediment surface samples from 13 sites, covering a growth temperature range of ∼0–28 °C. We selected mixed layer-dwelling and deep-dwelling species from a wide range of ocean settings to evaluate the feasibility of temperature reconstructions for different water depths. Various techniques to estimate foraminifer calcification temperatures were tested in order to assess their effects on the calibration and to find the most suitable approach. Results from this study generally confirm previous findings that there are no species-specific effects on the Δ47-temperature relationship in planktonic foraminifers, with one possible exception. Various morphotypes of Globigerinoides ruber were found to often deviate from the general trend determined for planktonic foraminifers. Our data are in excellent agreement with a recent foraminifer calibration study that was performed with a different analytical setup, as well as with a calibration based exclusively on benthic foraminifers. A combined, methodologically homogenized dataset also reveals very good agreement with an inorganic calibration based on travertines. Our findings highlight the potential of the Δ47 paleothermometer to be applied to recent and extinct species alike to study surface ocean temperatures as well as thermocline variability for a multitude of settings and time scales.

Description: Hydrogeological processes influence the morphology, mechanical behavior, and evolution of subduction margins. Fluid supply, release, migration, and drainage control fluid pressure and collectively govern the stress state, which varies between accretionary and nonaccretionary systems. We compiled over a decade of published and unpublished acoustic data sets and seafloor observations to analyze the distribution of focused fluid expulsion along the Hikurangi margin, New Zealand. The spatial coverage and quality of our data are exceptional for subduction margins globally. We found that focused fluid seepage is widespread and varies south to north with changes in subduction setting, including: wedge morphology, convergence rate, seafloor roughness, and sediment thickness on the incoming Pacific plate. Overall, focused seepage manifests most commonly above the deforming backstop, is common on thrust ridges, and is largely absent from the frontal wedge despite ubiquitous hydrate occurrences. Focused seepage distribution may reflect spatial differences in shallow permeability architecture, while diffusive fluid flow and seepage at scales below detection limits are also likely. From the spatial coincidence of fluids with major thrust faults that disrupt gas hydrate stability, we surmise that focused seepage distribution may also reflect deeper drainage of the forearc, with implications for pore-pressure regime, fault mechanics, and critical wedge stability and morphology. Because a range of subduction styles is represented by 800 km of along-strike variability, our results may have implications for understanding subduction fluid flow and seepage globally.

Description: How new subduction zones form is an ongoing scientific question with key implications for our understanding of how this process influences the behavior of the overriding plate. Here we focus on the effects of a Late Cretaceous subduction-initiation (SI) event in Iran and show how SI caused enough extension to open a back-arc basin in NE Iran. The Late Cretaceous Torbat-e-Heydarieh ophiolite (THO) is well exposed as part of the Sabzevar-Torbat-e-Heydarieh ophiolite belt. It is dominated by mantle peridotite, with a thin crustal sequence. The THO mantle sequence consists of harzburgite, clinopyroxene-harzburgite, plagioclase lherzolite, impregnated lherzolite, and dunite. Spinel in THO mantle peridotites show variable Cr# (10−63), similar to both abyssal and fore-arc peridotites. The igneous rocks (gabbros and dikes intruding mantle peridotite, pillowed and massive lavas, amphibole gabbros, plagiogranites and associated diorites, and diabase dikes) display rare earth element patterns similar to MORB, arc tholeiite and back-arc basin basalt. Zircons from six samples, including plagiogranites and dikes within mantle peridotite, yield U-Pb ages of ca. 99−92 Ma, indicating that the THO formed during the Late Cretaceous and was magmatically active for ∼7 m.y. THO igneous rocks have variable εNd(t) of +5.7 to +8.2 and εHf(t) ranging from +14.9 to +21.5; zircons have εHf(t) of +8.1 to +18.5. These isotopic compositions indicate that the THO rocks were derived from an isotopically depleted mantle source similar to that of the Indian Ocean, which was slightly affected by the recycling of subducted sediments. We conclude that the THO and other Sabzevar-Torbat-e-Heydarieh ophiolites formed in a back-arc basin well to the north of the Late Cretaceous fore-arc, now represented by the Zagros ophiolites, testifying that a broad region of Iran was affected by upper-plate extension accompanying Late Cretaceous subduction initiation.

Description: Deep-towed geophysical surveys require precise knowledge of navigational parameters such as instrument position and orientation because navigational uncertainties reflect in the data and therefore in the inferred geophysical properties of the subseafloor. We address this issue for the case of electrical conductivity inferred from controlled source electromagnetic data. We show that the data error is laterally variable due to irregular motion during deep towing, but also due to lateral variations in conductivity, including those resulting from topography. To address this variability and quantify the data error prior to inversion, we propose a 2-D perturbation study. Our workflow enables stable and geologically reliable results for multicomponent and multifrequency inversions. An error estimation workflow is presented, which comprises the assessment of navigational uncertainties, perturbation of navigational parameters, and forward modelling of electric field amplitudes for a homogeneous and then a heterogeneous subseafloor conductivity model. Some navigational uncertainties are estimated from variations of direct measurements. Other navigational parameters required for inversion are derived from the measured quantities and their error is calculated by means of error propagation. Some navigational parameters show direct correlation with the measured electric fields. For example, the antenna dip correlates with the vertical electric field and the depth correlates with the horizontal electric field. For the perturbation study each standard deviation is added to the navigational parameters. Forward models are run for each perturbation. Amplitude deviations are summed in quadrature with the stacking error for a total, laterally varying, data error. The error estimation is repeated for a heterogeneous subseafloor model due to the large conductivity range (several orders of magnitude), which affects the forward model. The approach enables us to utilize data from several components (multiple electric fields, frequencies and receivers) in the inversion to constrain the final model and reduce ambiguity. The final model is geologically reasonable, in this case enabling the identification of conductive metal sulphide deposits on the seafloor.

Description: Deformation during CO2 injection can lead to problems, like seismicity or fluid leaks, but small strains have the potential to be a useful signal for monitoring. The objective of this paper is to evaluate the possible evolution of the strain field during injection, and then assess existing and emerging techniques for measuring the strain field. Poroelastic analyses show that normal strains caused by injection into a reservoir are tensile in the vicinity of the well, but everywhere else at least one strain component is compressive. The vertical strain is compressive in the confining unit, and the radial strain decreases and changes sign from tensile to compressive with distance from the well. Tilting is away from the injection well at the ground surface, but it is towards the well overlying the reservoir. Methods for measuring in-situ strain include instruments that are grouted in the annulus between casing and wall rock (∼ 0.1 microstrain resolution), portable strain sensors that are temporarily clamped to the borehole wall (∼ 0.01 microstrain resolution), and strainmeters that are grouted in place (∼0.001 microstrain resolution). Instruments for measuring in-situ normal strains at the magnitudes and rates expected during injection are emerging, but they have yet to be fully evaluated in applications related to CO2 storage. In-situ strain data measured with emerging instruments promises to fill an important gap between the episodes of fast strain rates measured by seismic data, and the slow strains measured over relatively long periods of time by InSAR and GPS.

Description: Marine heatwaves have been observed worldwide and are expected to increase in both frequency and intensity due to climate change. Such events may cause ecosystem reconfigurations arising from species range contraction or redistribution, with ecological, economic and social implications. Macrophytes such as the brown seaweed Fucus vesiculosus and the seagrass Zostera marina are foundation species in many coastal ecosystems of the temperate northern hemisphere. Hence, their response to extreme events can potentially determine the fate of associated ecosystems. Macrophyte functioning is intimately linked to the maintenance of photosynthesis, growth and reproduction, and resistance against pathogens, epibionts and grazers. We investigated morphological, physiological, pathological and chemical defence responses of western Baltic Sea F. vesiculosus and Z. marina populations to simulated near‐natural marine heatwaves. Along with (a) the control, which constituted no heatwave but natural stochastic temperature variability (0HW), two treatments were applied: (b) two late‐spring heatwaves (June, July) followed by a summer heatwave (August; 3HW) and (c) a summer heatwave only (1HW). The 3HW treatment was applied to test whether preconditioning events can modulate the potential sensitivity to the summer heatwave. Despite the variety of responses measured in both species, only Z. marina growth was impaired by the accumulative heat stress imposed by the 3HW treatment. Photosynthetic rate, however, remained high after the last heatwave indicating potential for recovery. Only epibacterial abundance was significantly affected in F. vesiculosus. Hence both macrophytes, and in particular F. vesiculosus, seem to be fairly tolerant to short‐term marine heatwaves at least at the intensities applied in this experiment (up to 5°C above mean temperature over a period of 9 days). This may partly be due to the fact that F. vesiculosus grows in a highly variable environment, and may have a high phenotypic plasticity.

Description: Estuarine systems are of key importance for the riverine input of silicon (Si) to the ocean, which is a limiting factor of diatom productivity in coastal areas. This study presents a field dataset of surface dissolved Si isotopic compositions (30SiSi(OH)4) obtained in the estuaries of three of the world’s largest rivers, the Amazon (ARE), Yangtze (YRE), and Pearl (PRE), which cover different climate zones. While 30SiSi(OH)4 behaved conservatively in the YRE and PRE supporting a dominant control by water mass mixing, significantly increased 30SiSi(OH)4 signatures due to diatom utilization of Si(OH)4 were observed in the ARE and reflected a Si isotopic enrichment factor 30 of −1.0±0.4‰ (Rayleigh model) or −1.6±0.4‰ (steady state model). In addition, seasonal variability of Si isotope behavior in the YRE was observed by comparison to previous work and most likely resulted from changes in water residence time, temperature, and light level. Based on the 30 value obtained for the ARE, we estimate that the global average 30SiSi(OH)4 entering the ocean is 0.2-0.3‰ higher than that of the rivers due to Si retention in estuaries. This systematic modification of riverine Si isotopic compositions during estuarine mixing, as well as the seasonality of Si isotope dynamics in single estuaries, needs to be taken into account for better constraining the role of large river estuaries in the oceanic Si cycle.

Description: Highlights: • Assessment of the Indian Ocean simulation from global forced sea- ice models. • SST biases are 2 times smaller in forced simulations than the coupled simulations. • Coupled model shows large inter-model spread over the eastern equatorial Indian Ocean. • Refinement in model horizontal resolution does not significantly improve simulations. • Uncover a secondary pathway of northward cross-equatorial transport along 75 °E. • Models are unable to capture the observed thick barrier layer in the north Bay of Bengal. Abstract: We present an analysis of annual and seasonal mean characteristics of the Indian Ocean circulation and water masses from 16 global ocean–sea-ice model simulations that follow the Coordinated Ocean-ice Reference Experiments (CORE) interannual protocol (CORE-II). All simulations show a similar large-scale tropical current system, but with differences in the Equatorial Undercurrent. Most CORE-II models simulate the structure of the Cross Equatorial Cell (CEC) in the Indian Ocean. We uncover a previously unidentified secondary pathway of northward cross-equatorial transport along 75 °E, thus complementing the pathway near the Somali Coast. This secondary pathway is most prominent in the models which represent topography realistically, thus suggesting a need for realistic bathymetry in climate models. When probing the water mass structure in the upper ocean, we find that the salinity profiles are closer to observations in geopotential (level) models than in isopycnal models. More generally, we find that biases are model dependent, thus suggesting a grouping into model lineage, formulation of the surface boundary, vertical coordinate and surface salinity restoring. Refinement in model horizontal resolution (one degree versus degree) does not significantly improve simulations, though there are some marginal improvements in the salinity and barrier layer results. The results in turn suggest that a focus on improving physical parameterizations (e.g. boundary layer processes) may offer more near-term advances in Indian Ocean simulations than refined grid resolution.

Description: Microbial co‐cultivation is employed for awakening silent biosynthetic gene clusters (BGCs) to enhance chemical diversity. However, the selection of appropriate partners for co‐cultivation remains a challenge. Furthermore, competitive interactions involving the suppression of BGCs or upregulation of known, functional metabolite(s) during co‐cultivation efforts is also common. Herein, we performed an alternative approach for targeted selection of the best co‐cultivation pair. Eight marine sediment‐derived fungi were classified as strong or weak, based on their anti‐phytopathogenic potency. The fungi were co‐cultured systematically and analyzed for their chemical profiles and anti-phytopathogenic activity. Based on enhanced bioactivity and a significantly different metabolite profile including the appearance of a co‐culture specific cluster, the co‐culture of Plenodomus influorescens (strong) and Pyrenochaeta nobilis (weak) was prioritized for chemical investigation. Large‐scale co‐cultivation resulted in isolation of five polyketide type compounds: two 12‐membered macrolides, dendrodolide E (1) and its new analog dendrodolide N (2), as well as two rare azaphilones spiciferinone (3) and its new analog 8a-hydroxy-spiciferinone (4). A well‐known bis‐naphtho‐γ‐pyrone type mycotoxin, cephalochromin (5), whose production was specifically enhanced in the co-culture, was also isolated. Chemical structures of compounds 1–5 were elucidated by NMR, HRMS and [] 20/D analyses. Compound 5 showed the strongest anti‐phytopathogenic activity against Xanthomonas campestris and Phytophthora infestans with IC50 values of 0.9 and 1.7 µg/mL, respectively.

Description: We explore the predictability of tropical Atlantic sea surface temperature (SST) and the potential influence of climate model bias on SST predictions over the tropical Atlantic. Two statistical methods are used to examine the skill in forecasting tropical Atlantic SST anomalies (SSTAs): linear inverse modeling (LIM) and analogue forecast (AF). The statistical models are trained either with observations or with data from two control integrations of the Kiel Climate Model (KCM), which only differ with respect to the resolution of its atmospheric component. Observed SSTAs suggest that Tropical Atlantic climatic changes are potentially predictable at lead times of up to 6 months over large parts of the Tropical Atlantic. The SSTAs from the KCM version employing a high-resolution atmosphere model (KCM-HRES) is potentially predictable at a level comparable to that derived from the observations, whereas the SSTAs from the KCM version employing a low-resolution atmosphere model (KCM-LRES) is considerably less potentially predictable. We show that the enhanced potential predictability in the former KCM version can be very likely related to the improved representation of ENSO-like dynamics and its seasonality. We used the statistical models in true forecast mode, i.e. the prediction schemes were trained from data independent of the forecast period. Using observed SSTAs to train the LIM yields significant skill in forecasting observed SSTAs at lead times of up to 4 months across all calendar months, which is mostly restricted to the northern and equatorial western Tropical Atlantic. Similar patterns, but with lower skill, are found when the models’ SSTAs are used, in which LIM trained with the KCM-HRES generally yields higher skills than that from the KCM-LRES. Applying AF yields significant skills in predicting observed SSTAs over the same regions, but the forecast skills are considerably smaller. When the SSTAs together with either sea level pressure (SLP) anomalies or dynamic sea level (DSL) anomalies from the KCM are used to construct the statistical models, the prediction of observed equatorial Atlantic SSTAs can be improved, with significant skill enhancement at lead times of up to 4 months in limited regions. An optimal initial SSTA pattern is found, which results in the largest transient anomaly growth over the entire domain. Independent of external forces, this amplification is developed internally; meaning that the seasonal forecast might be more sensitive to initial conditions than currently thought.

Description: Tracking climate change and its relationships with chemical weathering and massive volcanic activity in deep-time greatly improves our understanding of the Earth's climate system. The Permo-Carboniferous period is a critical time interval with million year-scale glacial-deglacial cycles and massive basaltic volcanism, such as the Skagerrak-Centered (also named Skagerrak or Jutland) large igneous province. To explore the volcanism-climate interactions in this period, we obtained high precision CA-TIMS U-Pb zircon ages for three tuffaceous layers from a cored upper Pennsylvanian-lower Permian marginal marine succession in southern North China. These ages calibrate the Permo-Carboniferous biostratigraphy between ∼301–296 Ma in North China. From this dated core succession, mudrock samples and their calculated weathering index values were screened to constrain the weathering trends for the source landscapes and demonstrate a rapid increase with a subsequent decrease in source chemical weathering intensity during the period of ∼299 to 296.5 Ma. These trends coincide with the southern Gondwana glacial records, low latitude temperature changes, relative sea-level variations, and shifts in atmospheric pCO2 that together document an earliest Permian climate warming-cooling perturbation with a temperature maximum at ∼298 Ma. This climate warming in the Permo-Carboniferous icehouse correlates with the emplacement of the Skagerrak-Centered large igneous province, which likely released voluminous CO2 that led to climate warming during the Permo-Carboniferous transition. The immediately following cooling could possibly result from the rapid post-eruptional weathering of the massive basaltic rocks of this province in tropical latitudes, which would have sequestered atmospheric CO2 and promoted return to cooler icehouse conditions. This study supports the assertation that massive basaltic volcanism could first cause rapid climate warming and then may have an overall net cooling effect as previously suggested for the Deccan Traps and the Central Atlantic Magmatic Province.

Description: Highlights • High-Ti lavas have the same composition as Walvis Ridge and Gough Subtrack. • Low-Ti lavas are derived from a distinct source compare to the high-Ti lavas. • High-Ti and low-Ti basalts reflect the spatial zonation of the plume head. • Tristan-type composition has not been discovered in the plume head stage. • Sr-Nd-Pb-Hf isotopes from Etendeka flood basalts. Abstract The origin and distribution of geochemically distinct source components in continental flood volcanism (generally associated with the initial phase of a mantle plume head) are poorly understood. Here we present new geochemical (major and trace element and Sr-Nd-Pb-Hf isotope) data from the Etendeka flood basalts and associated dikes from northern and central Namibia that are believed to have been produced during the initial stage of the Tristan-Gough hotspot. Following earlier studies, the Etendeka lava flows and dikes are divided into high-Ti and low-Ti groups. The trace element and isotopic composition of the high-Ti tholeiitic basalts, exclusively outcropping in northern Etendeka (northwestern Namibia), are similar to the Gough-type enriched mantle I (EMI) composition found on the Walvis Ridge (the Atlantic type locality for the EMI end member). The low-Ti tholeiitic basalts, primarily outcropping in Southern Etendeka (central western Namibia), have higher 143Nd/144Nd and 207Pb/204Pb but lower 208Pb/204Pb ratios than the Gough composition. Combining our data with newly published 3He/4He data and estimates of the magma source’s potential temperature from 1520-1680◦C, we conclude that the source of the low-Ti basalts was also intrinsic to the Tristan-Gough plume, consistent with a spatially-zoned plume head. The low-Ti basalts were derived from a distinct EMI-type source component that has thus far only been detected in the initial Tristan-Gough plume head (∼132 Ma), but not the later submarine hotspot track.

Description: Oceanic island basalts are targeted for geochemical study because they provide a direct window into mantle composition and a wealth of information on the dynamics and timescales associated with Earth mixing. Previous studies mainly focused on the shield volcanic stage of oceanic islands and the more fusible, enriched mantle components that are easily distinguished in those basalts. Mantle depleted compositions are typically more difficult to resolve unless large amounts of this material participated in mantle melting (e.g., mid-ocean ridges), or unique processes allow for their compositions to be erupted undiluted, such as very small degrees of melting of a source with minimal fusible enriched components (e.g., rejuvenated basalts) or as xenoliths (e.g., abyssal peridotites). Mantle depleted components, defined here as material with low time-integrated Rb/Sr (low 87Sr/86Sr) and high time-integrated Sm/Nd and Lu/Hf ratios (high 143Nd/144Nd and 176Hf/177Hf) relative to primitive mantle, derive from a potentially very large volume reservoir (up to 80% of the mantle), and therefore need adequate characterization in order estimate the composition of the Earth and mantle-derived melts. This review focuses on mantle depleted compositions in oceanic island basalts using the Hawaiian-Emperor chain as a case study. The Hawaiian-Emperor chain is the ∼6000 km long geological record of the deeply sourced Hawaiian mantle plume, active for 〉81 Myr. Hawaiian volcanism evolves through four volcanic stages as a volcano traverses the Hawaiian plume: alkalic preshield, tholeiitic shield (80–90% volcano volume), alkalic postshield (∼1%), and silica undersaturated rejuvenated (〈0.1%). We report Pb-Sr-Nd-Hf isotope compositions and trace element concentrations of three rejuvenated Northwest Hawaiian Ridge basalts and compare them to an exhaustive compiled dataset of basalts from the Hawaiian Islands to the Emperor Seamounts. The Northwest Hawaiian Ridge (NWHR) includes 51 volcanoes spanning ∼42 m.y. between the bend in the Hawaiian-Emperor chain and the Hawaiian Islands where there is no high-precision isotopic data published on the rejuvenated-stage over ∼47% of the chain. NWHR and Hawaiian Island rejuvenated basalts are geochemically similar, indicating a consistent source for rejuvenated volcanism over ∼12.5 million years. In contrast, shield-stage basalts from the oldest Emperor Seamounts are more depleted in isotopic composition (i.e., higher 176Hf/177Hf, and 143Nd/144Nd with lower 87Sr/86Sr and 208Pb*/206Pb*) and trace element concentrations (i.e., much lower concentrations of highly incompatible elements) than all other depleted Hawaiian basalts younger than the bend, including NWHR rejuvenated basalts. The strongly depleted source for the oldest Emperor Seamounts (〉70 Ma) was likely related to interaction with the Kula-Pacific-Izanagi mid-ocean ridge spreading system active near the Hawaiian plume in the Late Cretaceous. In contrast, the incompatible trace element ratios of NWHR rejuvenated basalts require a distinct source in the Hawaiian mantle plume that was imprinted by ancient (〉1 Ga) partial melting, likely ancient recycled oceanic lithosphere. This review of the geochemistry of Hawaiian depleted components documents the need for the sampling of multiple distinctive depleted compositions, each preferentially melted during specific periods of Hawaiian plume activity. This suggests that the composition of depleted components can evolve during the lifetime of the mantle plume, as observed for enriched components in the Hawaiian mantle plume. Changes in the composition of depleted components are dominantly controlled by the upper mantle tectonic configurations at the time of eruption (i.e., proximity to a mid-ocean ridge), as this effect overwhelms the signal imparted by potentially sampling different lower mantle components through time.

Description: Along the Norwegian coasts and margins, extensive reefs of the stony coral Lophelia pertusa act as hotspots for local biodiversity. Climate models project that the temperature of Atlantic deep waters could rise by 1–3°C by 2100. In this context, understanding the effects of temperature on the physiology of cold-water species will help in evaluating their resilience to future oceanic changes. We investigated the response of L. pertusa to stepwise short-term increases in temperature. We sampled corals from four reefs, two located north of the Arctic circle and two at the mid-Norwegian shelf (boreal). In on-board experiments (one per reef), the sampled fragments were exposed to increasing temperatures from 5 to 15°C over 58 h. Respiration increased linearly by threefold for a 10°C increase. The short-term temperature increase did not induce mortality, cellular (neutral red assay for lysosome membrane stability; but one exception) or oxidative stress (lipid peroxidation assay) – to a few exceptions. However, the variability of the respiration responses depended on the experiment (i.e., reef location), possibly linked to the genetic structure of the individuals that we sampled (e.g., clones or siblings). The corals from the Arctic and boreal regions appear to have a high tolerance to the rapid temperature fluctuations they experience in the field. Over extended periods of time however, an increased metabolism could deplete the energy stored by the corals, if not met by an increased food availability and/or uptake. Empirical data on organisms’ thermal performance curves, such as the one presented in this study for L. pertusa, will be useful to implement predictive models on the responses of species and populations to climate change.

Description: Highlights • The syntectonic Otjimbingwe alkaline complex (Namibia) is ca. 545 Ma old. • Metasomatized mantle-derived melts are modified by AFC and accumulation processes. • The alkaline melts intruded during extensional tectonics during flat subduction. The ~545 Ma-old syn-collisional Otjimbingwe alkaline complex is composed of pyroxene-amphibole-biotite-bearing, mildly nepheline-normative to quartz-normative rocks ranging in composition from monzogabbro to monzonite, syenite and granite. The alkaline rocks have moderate to high SiO2 (50.5–73.0 wt%) and Na2O + K2O (5.1–11.5 wt%) and moderate to low MgO (6.6–0.2 wt%) concentrations. All samples have high large ion lithophile element (LILE: Ba up to 4600 ppm) and high-field-strength element contents (HFSE; Zr: 155–1328 ppm; Nb: 16–110 ppm; Ta: 1.4–7.1 ppm and Hf: 4–24 ppm) and have strongly fractionated LREE patterns ((La/Yb)N = 14–51). The most primitive members lack significant negative Eu anomalies. Mantle-normalized multi-element diagrams show depletion in Ba, Rb, Nb (Ta), P and Ti. The alkaline rocks have moderate radiogenic initial 87Sr/86Sr ratios (0.7061–0.7087) and unradiogenic initial ɛNd values (−3.9 to −6.1). This isotope signature, associated with high LREE/HFSE ratios indicates that the parental melts were generated in enriched portions of the shallow lithospheric mantle, which was probably affected by previous subduction zone processes. In addition, correlations between Sr and Nd isotopes indicate that some of these variations result from combined crustal assimilation and fractional crystallization (AFC) processes. A new model of flat subduction is presented that explains most of the unsolved problems in the orogenic evolution of the Damara orogen, namely (i) the absence of early intrusive rocks with a clear subduction zone setting, (ii) the absence of high-pressure rocks such as blueschists and eclogites, (iii) the unusual distribution of igneous rocks with a clear predominance of granite and granodiorite and (iv) the need for a asthenospheric window during a classical subduction to explain the high T/moderate P granulite facies conditions in the overriding plate.

Description: Glacial meltwater is an important source of bioessential trace elements to high latitude oceans. Upon delivery to coastal waters, glacially sourced particulate trace elements are processed during early diagenesis in sediments and may be sequestered or recycled back to the water column depending on local biogeochemical conditions. In the glaciated fjords of Svalbard, large amounts of reactive Fe and Mn (oxyhydr)oxides are delivered to the sediment by glacial discharge, resulting in pronounced Fe and Mn cycling concurrent with microbial sulfate reduction. In order to investigate the diagenetic cycling of selected trace elements (As, Co, Cu, Mo, Ni, and U) in this system, we collected sediment cores from two Svalbard fjords, Van Keulenfjorden and Van Mijenfjorden, in a transect along the head-to-mouth fjord axis and analyzed aqueous and solid phase geochemistry with respect to trace elements, sulfur, and carbon along with sulfate reduction rates. We found that Co and Ni associate with Fe and Mn (oxyhydr)oxides and enter the pore water upon reductive metal oxide dissolution. Copper is enriched in the solid phase where sulfate reduction rates are high, likely due to reactions with H2S and the formation of sulfide minerals. Uranium accumulates in the solid phase likely following reduction by both Fe- and sulfate-reducing bacteria, while Mo adsorbs to Fe and Mn (oxyhydr)oxides in the surface sediment and is removed from the pore water at depth where sulfidization makes it particle-reactive. Arsenic is tightly coupled to Fe redox cycling and its partitioning between solid and dissolved phases is influenced by competition with FeS for adsorption sites on crystalline Fe oxides. Differences in trace element cycling between the two fjords suggest delivery of varying amount and composition of tidewater glacier (Van Keulenfjorden) and meltwater stream (Van Mijenfjorden) material, likely related to oxidative processes occurring in meltwater streams. This processing produces a partially weathered, more reactive sediment that is subject to stronger redox cycling of Fe, Mn, S, and associated trace elements upon delivery to Van Mijenfjorden. With climate warming, the patterns of trace element cycling observed in Van Mijenfjorden may also become more prevalent in other Svalbard fjords as tidewater glaciers retreat into meltwater stream valleys.

Description: Nitric oxide (NO) is a short-lived intermediate of the oceanic nitrogen cycle. However, our knowledge about its production and consumption pathways in oceanic environments is rudimentary. In order to decipher the major factors affecting NO photochemical production, we irradiated several artificial seawater samples as well as 31 natural surface seawater samples in laboratory experiments. The seawater samples were collected during a cruise to the western tropical North Pacific Ocean (WTNP, a N-S section from 36 to 2 degrees N along 146 to 143 degrees E with 6 and 12 stations, respectively, and a W-E section from 137 to 161 degrees E along the Equator with 13 stations) from November 2015 to January 2016. NO photoproduction rates from dissolved nitrite in artificial seawater showed increasing trends with decreasing pH, increasing temperature, and increasing salinity. In contrast, NO photoproduction rates (average: 0.5 +/- 0.2 x 10(-12) mol L-1 s(-1)) in the natural seawater samples from the WTNP did not show any correlations with pH, water temperature, salinity, or dissolved inorganic nitrite concentrations. The flux induced by NO photoproduction in the WTNP (average: 13 x 10(-12) mol M-2 S-1) was significantly larger than the NO air-sea flux density (average: 1.8 x 10(-12) Mol M-2 S-1), indicating a further NO loss process in the surface layer.

Description: Highlights • Highly variable sea-ice conditions off eastern North Greenland during the Holocene. • The mid to late Holocene is characterized by seasonal to marginal sea-ice conditions. • Seasonal formation of the Northeast-Water (NEW) Polynya during the last 1 ka. Understanding the processes controlling the natural variability of sea ice in the Arctic, one of the most dynamic components of the climate system, can help to constrain the effects of future climate change in this highly sensitive area. For the first time, a high-resolution biomarker study was carried out to reconstruct past sea-ice variability off eastern North Greenland. This area is strongly influenced by cold surface waters and drift ice transported via the East Greenland Current, meltwater pulses from the outlet glaciers of the Northeast Greenland Ice Stream and the build-up of landfast ice. The well-dated Holocene sedimentary section of Core PS93/025 provides insights into variations of the sea-ice conditions (regional and local sea-ice signal), oceanic and atmospheric circulation and the biotic response to these changes. These biomarker records show a reduced to variable sea-ice cover during the early Holocene between 10.2 and 9.3 ka, followed by a steady increase in sea-ice conditions during the mid Holocene. During the last 5–6 ka, sea-ice conditions remained more stable representing a seasonal to marginal sea-ice situation. Based on our biomarker records, stable sea-ice edge conditions, with a fully developed polynya situation occurred since the last 1 ka.

Description: Variations of the solar spectral irradiance (SSI) with the 11-year sunspot cycle have been shown to have a significant impact on temperatures and the mixing ratios of atmospheric constituents in the stratosphere and mesosphere. Uncertainties in modelling the effects of SSI variations arise from uncertainties in the empirical models reconstructing the prescribed SSI data set as well as from uncertainties in the chemistry-climate model (CCM) formulation. In this study CCM simulations with the ECHAM MESSy Atmospheric Chemistry (EMAC) model and the Community Earth System Model 1 (CESM1) – Whole Atmosphere Chemistry Climate Model (WACCM) have been performed to quantify the uncertainties of the solar responses in chemistry and dynamics that are due to the usage of five different SSI data sets or the two CCMs. We apply a two-way analysis of variance (ANOVA) to separate the influence of the SSI data sets and the CCMs on the variability of the solar response in shortwave heating rates, temperature and ozone. The ANOVA identifies the SSI data set with the strongest influence on the variability of the solar signal in shortwave heating rates in the upper mesosphere and in the upper stratosphere/lower mesosphere. The strongest influence on the variability of the solar signal in ozone and temperature is identified in the upper stratosphere/lower mesosphere. The largest influence of the CCMs on variability of the solar responses can be identified in the upper mesosphere. The solar response in the lower stratosphere also depends on the CCM used, especially in the tropics and northern hemispheric subtropics and mid latitudes, where the model dynamics modulate the solar responses.

Description: Volcán Antuco (37°24′ S, 71°22′W; 2979 m asl) is the 13th ranked high threat volcano in Chile with 27 recorded historical eruptions, mostly (~96%) with volcanic explosivity indices (VEI) of ~1–2. An older eruptive record has been reconstructed from sections exposed on the western flank and is intimately related to a well-documented catastrophic sector collapse at ~7.2 cal ka BP. However, very little is known about Antuco's post-collapse eruptive history in other sectors, especially on the eastern flanks where prevalent westerly winds favor optimal eastward tephra transport and deposition. Our study reveals a more complete record of activity that has already been indicated from previous work with at least 23 tephra-forming explosive eruptions, most of them within the last c. 7.2 ka, including 4 events that have generated pyroclastic density currents that have widely inundated the lower eastern flanks. Tephra from these eruptive events are typically composed of scoria, free crystals and lithics, with occasional pumice. The composition of juvenile fragments varies between basalt and trachyandesite (50.2–62.2 wt% SiO2) and show phenocrysts of plagioclase, olivine and pyroxene. Our results show that most of the eruptions of Antuco (c. 79%) are Strombolian to violent Strombolian. These eruptions have an estimated longer repose times (c. 200 year) and are likely higher in magnitude than those registered during historical times. This study also shows that the composition, style and magnitude may change from one eruptive episode to the next. This eruptive variability seems in complete accord with recent findings from other centers in the Southern Volcanic Zone exhibiting similar temporal eruptive diversity and ultimately, has significant implications with respect to hazard assessment.

Description: Drill sites in the southern Bay of Bengal at 3°N 91°E (International Ocean Discovery Program Expedition 362) have sampled for the first time a complete section of the Nicobar Fan and below to the oceanic crust. This generally overlooked part of the Bengal–Nicobar Fan System may provide new insights into uplift and denudation rates of the Himalayas and Tibetan Plateau. The Nicobar Fan comprises sediment gravity‐flow deposits, mostly turbidites, that alternate with hemipelagite drapes and pelagite intervals of varying thicknesses. The decimetre‐thick to metre‐thick oldest pre‐fan sediments (limestones/chalks) dated at 69 Ma are overlain by volcanic material and slowly accumulated pelagites (0.5 g cm−2 kyr−1). At Expedition 362 Site U1480, terrigenous input began in the early Miocene at ca 22.5 Ma as muds, overlain by very thin‐bedded and thin‐bedded muddy turbidites at ca 19.5 Ma. From 9.5 Ma, sand content and sediment supply sharply increase (from 1–5 to 10–50 g cm−2 kyr−1). Despite the abundant normal faulting in the Nicobar Fan compared with the Bengal Fan, it offers a better‐preserved and more homogeneous sedimentary record with fewer unconformities. The persistent connection between the two fans ceased at 0.28 Ma when the Nicobar Fan became inactive. The Nicobar Fan is a major sink for Himalaya‐derived material. This study presents integrated results of International Ocean Discovery Program Expedition 362 with older Deep Sea Drilling Project/Ocean Drilling Program/International Ocean Discovery Program sites that show that the Bengal–Nicobar Fan System experienced successive large‐scale avulsion processes that switched sediment supply between the Bengal Fan (middle Miocene and late Pleistocene) and the Nicobar Fan (late Miocene to early Pleistocene). A quantitative analysis of the submarine channels of the Nicobar Fan is also presented, including their stratigraphic frequency, showing that channel size/area and abundance peaked at ca 2 to 3 Ma, but with a distinct low at 3 to 7 Ma: the intervening stratigraphic [sub]unit was a time of reduced sediment accumulation rates.

Description: Vertebrates are recognized as sentient beings. Consequently, urgent priority is now being given to understanding the needs and maximizing the welfare of animals under human care. The general health of animals is most commonly determined by physiological indices e.g., blood sampling, but may also be assessed by documenting behavior. Physiological health assessments, although powerful, may be stressful for animals, time-consuming and costly, while assessments of behavior can also be time-consuming, subject to bias and suffer from a poorly defined link between behavior and health. However, behavior is recognized as having the potential to code for stress and well-being and could, therefore, be used as an indicator of health, particularly if the process of quantifying behavior could be objective, formalized and streamlined to be time efficient. This study used Daily Diaries (DDs) (motion-sensitive tags containing tri-axial accelerometers and magnetometers), to examine aspects of the behavior of bycaught loggerhead turtles, Caretta caretta in various states of health. Although sample size limited statistical analysis, significant behavioral differences (in terms of activity level and turn rate) were found between “healthy” turtles and those with external injuries to the flippers and carapace. Furthermore, data visualization (spherical plots) clearly showed atypical orientation behavior in individuals suffering gas emboli and intestinal gas, without complex data analysis. Consequently, we propose that the use of motion-sensitive tags could aid diagnosis and inform follow-up treatment, thus facilitating the rehabilitation process. This is particularly relevant given the numerous rehabilitation programs for bycatch sea turtles in operation. In time, tag-derived behavioral biomarkers, TDBBs for health could be established for other species with more complex behavioral repertoires such as cetaceans and pinnipeds which also require rehabilitation and release. Furthermore, motion-sensitive data from animals under human care and wild conspecifics could be compared in order to define a set of objective behavioral states (including activity levels) for numerous species housed in zoos and aquaria and/or wild species to help maximize their welfare.

Description: The generation of magmas in the East African Rift System (EARS) is largely the result of either: (A) melting of easily fusible compositions located within the lithospheric mantle due to thermobaric perturbations of the lithosphere, or (B) melting of the convecting upper mantle due to decompression caused by thinning of the plate during extension. Melt generated from amphibole- or phlogopite-bearing metasomes within the lithospheric mantle yields alkaline, silica-undersaturated lavas, while more silica-saturated lavas are primarily a function of melting material within the convecting upper mantle. Sourcing of silica-undersaturated melts within the lithospheric mantle is consistent with the observed tendency for initial melts within any given region to exhibit trace element characteristics consistent with melting of lithospheric metasomes, likely reflecting the initial destabilization and thinning of the lithospheric mantle. With continued lithospheric thinning, the trend towards more silica-saturated compositions coincides with a shift towards compositions interpreted as melting of the convecting upper mantle. Contributions from these two sources may oscillate where extension is pulsed – melts of the convecting upper mantle are favored during periods of plate thinning; melting of either existing or recently formed metasomes may be favored during periods of relative extensional quiescence. The isotopic systematics of East African magmatism reveals significant complexity as to the specific reservoirs that may participate in the melting processes noted above. The lithospheric mantle beneath East Africa has undergone enrichment through the percolation of sub-lithospheric derived melts and fluids over an extended interval, which close to the Tanzania craton, has resulted in a layered lithospheric mantle exhibiting extreme isotopic ratios. Elsewhere, the lithospheric mantle has also undergone enrichment but given the more juvenile age of this lithosphere, less extreme isotopic values have developed. Material rising from the African Large Low Shear Velocity Province (LLSVP) has also metasomatized the lithospheric mantle, and thus lavas exhibiting a trace element signature linked to melting within the lithospheric mantle may exist as any number of reservoirs or mixtures of the same. Material derived from the convecting upper mantle incorporates the Afar Plume endmember, a depleted mantle endmember, and some form of lithospheric endmember. The isotopic characteristics of magma suites from throughout the region form arrays that broadly converge on the composition of the Afar Plume, despite some complexity where the plume material has formed a hybrid plume-lithosphere component. The convergence of these arrays strongly supports a model whereby the prevalent composition of material rising from the African LLSVP beneath the EARS is broadly equivalent to the composition of the Afar Plume.

Description: The current increase in atmospheric CO2 concentration induces changes in the seawater carbonate system resulting in decreased pH and calcium carbonate saturation state, a phenomenon called ocean acidification (OA). OA has long been considered as a major threat to echinoderms because their extensive endoskeleton is made of high‑magnesium calcite, one of the most soluble forms of calcium carbonate. Numerous studies addressed this question in sea urchins, but very few questioned the impact of OA on the sea star skeleton, although members of this taxon do not compensate their extracellular pH, contrary to most sea urchins. In the present study, adults of the common sea star, Asterias rubens from Kiel Fjord, a site experiencing natural acidification events exceeding pCO2 levels of 2500 μatm, were chronically exposed to different levels of simulated ocean acidification (pHT-SW 8.0, 7.4, 7.2), encompassing present and future conditions, for the duration of 109 days. Corrosion and mechanical properties of skeletal elements were studied using scanning electron microscopy, three-point bending tests as well as nanoindentation. The spines were significantly corroded at pHT-SW 7.4 and below while the ambulacral plates were only affected at pHT-SW 7.2. Nanoindentation of newly formed spines and ambulacral plates did not reveal significant CO2-induced differences in skeleton hardness or elasticity across treatments. Results of three-point bending tests revealed significantly reduced characteristic strength and fracture force of ambulacral plates from the median arm segment at pHT-SW 7.4 and below. These plates are those supporting the tube feet involved in the opening of bivalves during feeding and in the animal attachment to the substrate. Under reduced seawater pH, this might result in fracture of sea star plates during predation on mussel. The present results predict a possible impact of ocean acidification on the skeletal integrity of a marine keystone predator.

Description: In this study, we conducted an experimental panel survey in Norway, Germany and Portugal to explore consumers' willingness to pay more for products that are certified microplastic free. This is placed within the context of private certification schemes and private governance as mechanisms to increase consumer conscientiousness, establish a higher environmental standard in terms of microplastic and reduce marine pollution. We find that consumers in general are very conscious about the issue, would generally prefer products that are microplastics free, but would seldom choose these when there is a price premium on the label. This had a geographical offset though, with the results aligning with that of political trust in the nation, with Norwegians being less likely to purchase items with price premiums for private governance labels, and Portugal being most likely to – even with a price premium.

Description: Slow slip events (SSEs) accommodate a significant proportion of tectonic plate motion at subduction zones, yet little is known about the faults that actually host them. The shallow depth (〈2 km) of well-documented SSEs at the Hikurangi subduction zone offshore New Zealand offers a unique opportunity to link geophysical imaging of the subduction zone with direct access to incoming material that represents the megathrust fault rocks hosting slow slip. Two recent International Ocean Discovery Program Expeditions sampled this incoming material before it is entrained immediately down-dip along the shallow plate interface. Drilling results, tied to regional seismic reflection images, reveal heterogeneous lithologies with highly variable physical properties entering the SSE source region. These observations suggest that SSEs and associated slow earthquake phenomena are promoted by lithological, mechanical, and frictional heterogeneity within the fault zone, enhanced by geometric complexity associated with subduction of rough crust.

Description: The generation of reliable age models for palaeoenvironmental and archaeological records in the Eurasian Arctic is often problematic when using conventional dating techniques. Tephrochronology can potentially improve the chronologies of such records and synchronise disparate sedimentary archives. However, to date, systematic tephra studies are lacking for this region. This paper presents the first cryptotephra data from the White Sea region (northwestern Russia) based on a peat core spanning the past ~1800 years. We identify seven geochemical glass populations that derive from six Icelandic volcanoes and correlate four of them to north European tephra isochrons; these include Askja ad 1875, the basaltic component of the ad 877 Landnám tephra, and tephras BTD‐15 (c. ad 1750–1650) and SL‐2/SB‐2 (ad 803–767) from unknown eruptions of Katla and Snæfellsjökull, respectively. The remaining three populations originate from Grímsvötn, Hekla and Katla; however, their attribution to individual eruptions remains ambiguous. These findings highlight the potential to extend the Late Holocene tephrochronological framework of northern Europe to the west Eurasian Arctic. The detection of at least three basaltic tephras in the core suggests that basaltic shards can be transported over larger distances than previously known and that peatlands are well suited to preserve such components.

Description: The 1888 Ritter Island volcanic sector collapse triggered a regionally damaging tsunami. Historic eyewitness accounts allow the reconstruction of the arrival time, phase and height of the tsunami wave at multiple locations around the coast of New Guinea and New Britain. 3D seismic interpretations and sedimentological analyses indicate that the catastrophic collapse of Ritter Island was preceded by a phase of deep-seated gradual spreading within the volcanic edifice and accompanied by a submarine explosive eruption, as the volcanic conduit was cut beneath sea level. However, the potential impact of the deep-seated deformation and the explosive eruption on tsunami genesis is unclear. For the first time, it is possible to parameterise the different components of the Ritter Island collapse with 3D seismic data, and thereby test their relative contributions to the tsunami. The modelled tsunami arrival times and heights are in good agreement with the historic eyewitness accounts. Our simulations reveal that the tsunami was primarily controlled by the displacement of the water column by the collapsing cone at the subaerial-submarine boundary and that the submerged fraction of the slide mass and its mobility had only a minor effect on tsunami genesis. This indicates that the total slide volume, when incorporating the deep-seated deforming mass, is not directly scalable for the resulting tsunami height. Furthermore, the simulations show that the tsunamigenic impact of the explosive eruption energy during the Ritter Island collapse was only minor. However, this relationship may be different for other volcanogenic tsunami events with smaller slide volumes or larger magnitude eruptions, and should not be neglected in tsunami simulations and hazard assessment.

Description: Seamount phosphates are increasingly regarded as potential resources for rare earth elements (REE) and plus yttrium (REY). Carbonate fluorapatite (CFA) formed within seamount ferromanganese (FeMn) crusts is the most common seamount phosphate mineral. However, reports on the mineralogy and geochemistry of CFA are few and thus its origin and acquisition of trace elements are not well understood. In this study, we analyzed the major and trace elements of CFA in FeMn crusts collected from Western and Central Pacific seamounts to investigate the genesis of trace elements in the CFA. This is the first study to use in situ analytical techniques such as electron microprobe analyzer (EPMA) and laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) to analyze seamount CFA. We found that the CFA hosts abundant minor and trace elements and propose that ionic substitutions are responsible for the high contents of SO3, SiO2, REY, Sr, Na, Fe, and Mn in the CFA veins found in the FeMn crusts, i.e., SiO32− and SO42− substitute for PO42−, while REE3+, Y3+, Na+, Fe2+, and Mn2+ substitute for Ca2+. REE3+ substitutions for Ca2+ in the CFA are charge-compensated by Na+ substitution for Ca2+. Fourier transform infrared spectroscopy (FTIR) analysis shows that CO32– mainly substitutes for PO42− in the CFA crystal structure, and there is a minor substitution of PO42− by CO3F3−. Ocean water is the major source of the P and REY, which when precipitated as seamount CFA is characterized by high ∑REE (345 to 6016 ppm) and heavy-REE (HREE) enrichments. Monazite grains dispersed in the seamount CFA contribute trace amount of REY. These results shed light on the composition and element mobility of seamount CFA with economic potential, which also provides valuable insights into global ocean chemical cycling (e.g. REE).

Description: The desiccation tolerance of the intertidal seagrass Zostera japonica has been demonstrated in a number of studies; however, the factors limiting expansion of intertidal seagrass species into subtidal zones remain controversial. We transplanted Z. japonica shoots from the intermediate intertidal zone into the plots with and without Z. marina shoots in both the lower intertidal and shallow subtidal zones to investigate the factors controlling Z. japonica growth in these zones. Daily photon flux density at the Z. japonica canopy level was attenuated by both water depth and coexisting Z. marina shoots but more strongly by Z. marina shoots than water depth in the transplant plots. The shoot density and biomass of Z. japonica transplants were significantly lower in transplant plots in the subtidal zone than in the lower intertidal zone. Although the photon flux density was significantly lower in transplant plots containing Z. marina shoots, the growth of Z. japonica transplants did not differ significantly between plots with and those without Z. marina shoots. Z. japonica transplants exhibited photoacclimatory responses such as increased shoot height and chlorophyll content under the lower-light conditions, offsetting the reduced light availability so that no significant differences in transplant growth occurred between plots with and those without Z. marina shoots. As the growth of Z. japonica transplants decreased significantly in the subtidal zone, the interactive effects of environmental stresses associated with tidal inundation and reduced light availability may restrict penetration of the intertidal seagrass Z. japonica into the subtidal zone. The persistence of high photosynthetic performance after air exposure and a regular arrangement of the densely overlapped leaves atop wet sediments may be desiccation tolerance mechanisms for Z. japonica in the intertidal zone.

Description: Iron (Fe) biogeochemistry in marine sediments is driven by redox transformations creating Fe(II) and Fe(III) gradients. As sediments are physically mixed by wave action or bioturbation, Fe gradients re-establish regularly. In order to identify the response of dissolved Fe(II) (Fe2+) and Fe mineral phases toward mixing processes, we performed voltammetric microsensor measurements, sequential Fe extractions, and Mössbauer spectroscopy of 12 h light-dark cycle incubated marine coastal sediment. Fe2+ decreased during 7 days of undisturbed incubation from approximately 400 to 60 μM. In the first 2-4 days of incubation, Fe2+ accumulated up to 100 μM in the top 2 mm due to Fe(III) photoreduction. After physical perturbation at day 7, Fe2+ was re-mobilized reaching concentrations of 320 μM in 30 mm depth, which decreased to below detection limit within 2 days afterward. Mössbauer spectroscopy showed that the relative abundance of metastable iron-sulfur mineral phases (FeSx) increased during initial incubation and decreased together with pyrite (FeS2) after perturbation. We show that Fe2+ mobilization in marine sediments is stimulated by chemical changes caused by physical disturbances impacting the Fe redox distribution. Our study suggests that, in addition to microbial and abiotic Fe(III) reduction, including Fe(III) photoreduction, physical mixing processes induce chemical changes providing sediments and the inhabiting microbial community with Fe2+.

Description: Enrichment of the oceans with CO2 may be beneficial for some marine phytoplankton, including harmful algae. Numerous laboratory experiments provided valuable insights into the effects of elevated pCO(2) on the growth and physiology of harmful algal species, including the production of phycotoxins. Experiments close to natural conditions are the next step to improve predictions, as they consider the complex interplay between biotic and abiotic factors that can confound the direct effects of ocean acidification. We therefore investigated the effect of ocean acidification on the occurrence and abundance of phycotoxins in bulk plankton samples during a long-term mesocosm experiment in the Gullmar Fjord, Sweden, an area frequently experiencing harmful algal blooms. During the experimental period, a total of seven phycotoxin-producing harmful algal genera were identified in the fjord, and in accordance, six toxin classes were detected. However, within the mesocosms, only domoic acid and the corresponding producer Pseudo-nitzschia spp. was observed. Despite high variation within treatments, significantly higher particulate domoic acid contents were measured in the mesocosms with elevated pCO(2). Higher particulate domoic acid contents were additionally associated with macronutrient limitation. The risks associated with potentially higher phycotoxin levels in the future ocean warrants attention and should be considered in prospective monitoring strategies for coastal marine waters.

Description: Climate engineering (CE) measures are increasingly discussed when dealing with the adverse impacts of climate change. While much research has focused on individual methods, few studies attempt to compare and rank the effectiveness of these measures. Furthermore, model uncertainties are seldom acknowledged and lesser still, estimated when CE scenarios are assessed. In this work, we quantify the variance in outcomes due to poorly constrained model parameters under several idealized CE scenarios. The four scenarios considered are (1) warming under the high emission scenario Representative Concentration Pathway 8.5 without CE applied and the same emission scenario with (2) afforestation,(3) solar radiation management, and (4) artificial ocean alkalinization. By considering the parametric uncertainty in model outputs, we demonstrate the problems with comparing these scenarios using a single parameter setting. Using statistical emulation, we estimate the probability distributions of several model outcomes. Based on such distributions, we suggest an approach to ranking the effectiveness of the scenarios considered according to their probability of avoiding climate thresholds.

Description: A new estimate of Agulhas leakage transport is calculated using profiling floats and drifters. Since Richardson's seminal estimate of 15 Sv in 2007, the number of floats and drifters passing through the Agulhas Current has quadrupled. Within uncertainties we find the same leakage percentages as Richardson, with 34% of drifters leaking at the surface and 21% of floats leaking at 1,000 m depth. We find that the drifters tend to follow a northward leakage pathway via the Benguela Current compared to the northwestward leakage pathway of the floats along the Agulhas Ring corridor. We simulate the isobaric and profiling behavior of the floats and drifters using two high resolution models and two offline Lagrangian tracking tools, quantifying for the first time the sampling biases associated with the observations. We find that the isobaric bias cannot be robustly simulated but likely causes an underestimate of observed leakage by one or two Sverdrups. The profiling behavior of the floats causes no significant bias in the leakage. Fitting a simulated vertical leakage profile to the observed leakage percentages from the floats and drifters and using the mean Agulhas transport observed by a moored array at 34°S we find an improved Agulhas leakage transport of 21.3 Sv, with an estimated error of 4.7 Sv. Our new leakage transport is higher primarily because we account for leakage at depths down to 2,000 m, while Richardson considered only the top 1,000 m of the water column.

Description: Upwelling ocean currents associated with oxygen minimum zones (OMZs) supply nutrients fuelling intense marine productivity. Perturbations in the extent and intensity of OMZs are projected in the future, but it is currently uncertain how this will impact fluxes of redox‐sensitive trace metal micronutrients to the surface ocean. Here we report seawater concentrations of Fe, Mn, Co, Cd, and Ni alongside the redox indicator iodide/iodate in the Peruvian OMZ during the 2015 El Niño event. The El Niño drove atypical upwelling of oxygen‐enriched water over the Peruvian Shelf, resulting in oxidized iodine and strongly depleted Fe (II), total dissolved Fe, and reactive particulate Fe concentrations relative to non‐El Niño conditions. Observations of Fe were matched by the redox‐sensitive micronutrients Co and Mn, but not by non‐redox‐sensitive Cd and Ni. These observations demonstrate that oxygenation of OMZs significantly reduces water column inventories of redox‐sensitive micronutrients, with potential impacts on ocean productivity. Plain Language Summary Some trace metals, including iron, are essential micronutrients for phytoplankton growth. However, the solubility of iron is very low under oxygenated conditions. Consequently, restricted iron availability in oxygen‐rich seawater can limit phytoplankton growth in the ocean, including in the Eastern Tropical South Pacific. Under typical conditions, depleted oxygen on the South American continental shelf is generally thought to enhance iron supply to the ocean, fuelling phytoplankton productivity in overlying waters. However, the impact of changes in oxygenation, which are predicted to occur in the future, are not known. The 2015 El Niño event led to unusually high oxygen on the Peruvian shelf, offering a system‐scale test on how oxygen influences seawater iron concentrations. We show that El Niño‐driven oxygenation resulted in marked decreases in iron and other metals sensitive to oxygen (cobalt and manganese), whilst metals not sensitive to oxygen (cadmium and nickel) were unaffected. The measured reductions in iron may have led to decreased phytoplankton productivity.

Description: The earliest part of the Holocene, from 11.5k to 7k (k = 1000 years before present), is a critical transition period between the relatively cold last deglaciation and the warm middle Holocene. It is marked by more pronounced seasonality and reduced greenhouse gases (GHGs) than the present state, as well as by the presence of the Laurentide Ice Sheet (LIS) and glacial meltwater perturbation. This paper performs experiments under pre-industrial and different early-Holocene regimes with AWI-ESM (Alfred Wegener Institute–Earth System Model), a state-of-the-art climate model with unstructured mesh and varying resolutions, to examine the sensitivity of the simulated Atlantic meridional overturning circulation (AMOC) to early-Holocene insolation, GHGs, topography (including properties of the ice sheet), and glacial meltwater perturbation. In the experiments with early-Holocene Earth orbital parameters and GHGs applied, the AWI-ESM simulation shows a JJA (June–July–August) warming and DJF (December–January–February) cooling over the mid and high latitudes compared with pre-industrial conditions, with amplification over the continents. The presence of the LIS leads to an additional regional cooling over the North America. We also simulate the meltwater event around 8.2k. Big discrepancies are found in the oceanic responses to different locations and magnitudes of freshwater discharge. Our experiments, which compare the effects of freshwater release evenly across the Labrador Sea to a more precise injection along the western boundary of the North Atlantic (the coastal region of LIS), show significant differences in the ocean circulation response, as the former produces a major decline of the AMOC and the latter yields no obvious effect on the strength of the thermohaline circulation. Furthermore, proglacial drainage of Lakes Agassiz and Ojibway leads to a fast spin-down of the AMOC, followed, however, by a gradual recovery. Most hosing experiments lead to a warming over the Nordic Sea and Barents Sea of varying magnitudes, because of an enhanced inflow from lower latitudes and a northward displacement of the North Atlantic deep convection. These processes exist in both of our high- and low-resolution experiments, but with some local discrepancies such as (1) the hosing-induced subpolar warming is much less pronounced in the high-resolution simulations; (2) LIS coastal melting in the high-resolution model leads to a slight decrease in the AMOC; and (3) the convection formation site in the low- and high-resolution experiments differs, in the former mainly over northeastern North Atlantic Ocean, but in the latter over a very shallow subpolar region along the northern edge of the North Atlantic Ocean. In conclusion, we find that our simulations capture spatially heterogeneous responses of the early-Holocene climate.

Description: Massive cyanobacteria blooms occur almost every summer in the Baltic Sea but the capability to quantitatively predict their extent and intensity is poorly developed. Here we analyse statistical relationships between multi-decadal satellite-derived time series of the frequency of cyanobacteria surface accumulations (FCA) in the central Baltic Sea Proper and a suite of environmental variables. Over the decadal scale (∼5-20 years) FCA was highly correlated (R2 ∼ 0.69) with a set of biogeochemical variables related to the amount of phosphorus and hypoxia in bottom layers. Water temperature in the surface layer was also positively correlated with FCA at the decadal scale. In contrast, the inter-annual variations in FCA had no correlation with the biogeochemical variables. Instead, significant correlations were found with the solar shortwave direct flux in July and the sea-surface temperature, also in July. It thus appears that it is not possible to predict inter-annual fluctuations in cyanobacteria blooms from water chemistry. Moreover, environmental variables could only explain about 45% of the inter-annual variability in FCA, probably because year-to-year variations in FCA are significantly influenced by biological interactions.

Description: Studies integrating mangrove in-situ observations and remote sensing analysis for specific sites often lack precise estimates of carbon stocks over time frames that include disturbance events. This study quantifies change in mangrove area from 1985 to 2018 with Landsat time series analysis, estimates above and belowground stored carbon using field data, and evaluates aboveground carbon stock changes after the 2004 Category 4, Hurricane Charley, in J.N. “Ding” Darling National Wildlife Refuge. Two allometric equation methods yielding similar results were used to estimate aboveground carbon content in three mangrove species found in the refuge. Aboveground carbon contained 67 (SE = 2) MgC ha−1 with a total refuge estimate of 74,504 MgC in 2018. Sediment contained 259 (SE = 28) MgC ha−1 for a total of 288,008 MgC in the refuge. The initial reduction in mangrove area caused by Hurricane Charley was between 0.6% and 5.3%, equivalent to between 427 MgC and 3,599 MgC under three different scenarios of carbon loss. As a result of the hurricane, approximately 61 ha of mangroves were disturbed, of which 24 ha had recovered by 2018, with 37 ha (~3% of the pre-hurricane mangrove area) still not recovered 14 years after the event. The 37 ha of mangroves that have not recovered are located in a tidally restricted area of the refuge. A longer recovery time in this area will likely result in a greater loss of carbon storage than in the rest of the refuge.

Description: Highlights • Geochemically diverse Late Cretaceous small-volume magmatism in the Sava-Vardar Zone. • Late Cretaceous ultrapotassic lava, equivalent of minette and kersantite. • Magma derivation from a LREE and K enriched, garnet-bearing anciently metasomatized mantle source. • Magmatism occurred either in a fore-arc setting or is associated with transtensional tectonics. Abstract Late Cretaceous global plate reorganization associated with the inception of counterclockwise rotation of Africa relative to Europe initiated in the Balkan region small-volume magmatism of diverse geochemical signature along the enigmatic Sava-Vardar Zone. We study a Late Cretaceous lamprophyric sill in Ripanj village near Belgrade to constrain this magmatic episode. The lamprophyre is characterized by high contents of Na, P, Fe and Al, and low contents of K, Ca and Mg. Its original nature (Na, K, Ca and Mg) is concealed by intense alteration (albitization of feldspar and partial chloritization of phlogopite) that erased the ultrapotassic affinity of the rocks and resulted in extremely low K/Na ratios. The recalculated chemical composition demonstrates that the rocks are ultrapotassic, with K2O and MgO 〉3 wt % and K2O/Na2O 〉 2, and belong to the durbachite-vaugnerite series, i. e., the plutonic equivalents of minettes and kersantites. Two phlogopite concentrates gave Ar–Ar ages of 86.80 ± 0.5 Ma and 86.90 ± 0.5 Ma. Our combined elemental and Sr–Nd–Pb isotope data (87Sr/86Sr 0.70667–0.70677, 143Nd/144Nd 0.512426–0.512429, 206Pb/204Pb 18.82–19.13, 207Pb/204Pb 15.67–15.68, 208Pb/204Pb 38.92–39.19) for representative lamprophyric samples suggests magma derivation from a light rare earth elements (LREE) and K enriched, metasomatized mantle source. The content of LREE of the rocks is enriched, whereas heavy rare earth elements (HREE) is depleted. Rare earth elements (REE) of the whole rock and REE of diopside all indicate that garnet was present in their source. There are two viable and mutually-excluding geodynamic scenarios for the Late Cretaceous magmatism in the Balkans: (i) If the Sava-Vardar ocean still existed in the Late Cretaceous and was subducted under the European plate with arc volcanism along the Apuseni-Banat-Timok-Panagyurishte-Srednjogorje belt, coeval magmatism in the Sava-Vardar Zone occurred in a fore-arc setting, and may be related to ridge subduction; (ii) If the Mesozoic ocean closed already during the Upper Jurassic or Lower Cretaceous, the Late Cretaceous volcanism within the Sava-Vardar Zone represents intracontinental volcanism associated with transtensional tectonics.

Description: The Hikurangi Margin off the east coast of the North Island (Te Ika-a-Māui) is a tectonically active subduction zone and the location of New Zealand’s largest gas hydrate province. Faults are internally complex volumetric zones that may play a significant role in the migration of fluids beneath the seafloor. The combined processes of deformation and fluid migration result in the formation of concentrated hydrate accumulations along accretionary ridges. It is not fully understood to what extent faults control fluid migration along the Hikurangi Margin, and whether deep-seated thrust faults provide a pathway for thermogenic gas to migrate up from sources at depth. Using 2D models based on seismic data from the region we investigated the role of thrust faults in facilitating fluid migration and contributing to the formation of concentrated gas hydrates. By altering permeability properties of the fault zones in these transient state models we can determine whether faults are required to act as fluid flow pathways. In this study we focus on two study sites offshore southern Wairarapa, using realistic yet simplified fault geometries derived from 2D seismic lines. The results of these models allow us to start to disentangle the complex relationship between fault zone structure, permeability, geometry, fluid migration and gas hydrate formation. Based on the model outputs we propose that faults act as primary pathways facilitating fluid migration and are critical in the formation of concentrated gas hydrate deposits.

Description: The causes of the seasonal cycle of vertical turbulent cooling at the base of the mixed layer are assessed using observations from moored buoys in the tropical Atlantic Intertropical Convergence Zone (ITCZ) (4°N, 23°W) and trade wind (15°N, 38°W) regions together with mixing parameterizations and a one-dimensional model. At 4°N the parameterized turbulent cooling rates during 2017–2018 and 2019 agree with indirect estimates from the climatological mooring heat budget residual: both show mean cooling of 25–30 W m (Formula presented.) during November–July, when winds are weakest and the mixed layer is thinnest, and 0–10 W m (Formula presented.) during August–October. Mixing during November–July is driven by variability on multiple time scales, including subdiurnal, near-inertial, and intraseasonal. Shear associated with tropical instability waves (TIWs) is found to generate mixing and monthly mean cooling of 15–30 W m (Formula presented.) during May–July in 2017 and 2019. At 15°N the seasonal cycle of turbulent cooling is out of phase compared to 4°N, with largest cooling of up to 60 W m (Formula presented.) during boreal fall. However, the relationships between wind speed, mixed layer depth, and turbulent mixing are similar: weaker mean winds and a thinner mixed layer in the fall are associated with stronger mixing and turbulent cooling of SST. These results emphasize the importance of seasonal modulations of mixed layer depth at both locations and shear from TIWs at 4°N.

Description: Coastal areas contribute significantly to the emissions of methane (CH4) from the ocean. In order to decipher its temporal variability in the whole water column, dissolved CH4 was measured on a monthly basis at the Boknis Eck Time-series Station (BE) located in the Eckernförde Bay (SW Baltic Sea) from 2006 to 2017. BE has a water depth of about 28 m and dissolved CH4 was measured at six water depths ranging from 0 to 25 m. In general CH4 concentrations increased with depth, indicating a sedimentary release of CH4. Pronounced enhancement of the CH4 concentrations in the bottom layer (15–25 m) was found during February, May–June and October. CH4 was not correlated with Chlorophyll a or O2 over the measurement period. Unusually high CH4 concentrations (of up to 696 nM) were sporadically observed in the upper layer (0–10 m) (e.g. in November 2013 and December 2014) and were coinciding with Major Baltic Inflow (MBI) events. Surface CH4 concentrations were always supersaturated throughout the monitoring period, indicating that the Eckernförde Bay is an intense but highly variable source of atmospheric CH4. We did not detect significant temporal trends in CH4 concentrations or emissions, despite of ongoing environmental changes such as warming and deoxygenation in the Eckernförde Bay. Overall, the CH4 variability at BE is driven by a complex interplay of various biological and physical processes.

Description: The extracellular concentration of H2O2 in surface aquatic environments is controlled by a balance between photochemical production and the microbial synthesis of catalase and peroxidase enzymes to remove H2O2 from solution. In any kind of incubation experiment, the formation rates and equilibrium concentrations of reactive oxygen species (ROSs) such as H2O2 may be sensitive to both the experiment design, particularly to the regulation of incident light, and the abundance of different microbial groups, as both cellular H2O2 production and catalase–peroxidase enzyme production rates differ between species. Whilst there are extensive measurements of photochemical H2O2 formation rates and the distribution of H2O2 in the marine environment, it is poorly constrained how different microbial groups affect extracellular H2O2 concentrations, how comparable extracellular H2O2 concentrations within large-scale incubation experiments are to those observed in the surface-mixed layer, and to what extent a mismatch with environmentally relevant concentrations of ROS in incubations could influence biological processes differently to what would be observed in nature. Here we show that both experiment design and bacterial abundance consistently exert control on extracellular H2O2 concentrations across a range of incubation experiments in diverse marine environments. During four large-scale (〉1000 L) mesocosm experiments (in Gran Canaria, the Mediterranean, Patagonia and Svalbard) most experimental factors appeared to exert only minor, or no, direct effect on H2O2 concentrations. For example, in three of four experiments where pH was manipulated to 0.4–0.5 below ambient pH, no significant change was evident in extracellular H2O2 concentrations relative to controls. An influence was sometimes inferred from zooplankton density, but not consistently between different incubation experiments, and no change in H2O2 was evident in controlled experiments using different densities of the copepod Calanus finmarchicus grazing on the diatom Skeletonema costatum (〈1 % change in [H2O2] comparing copepod densities from 1 to 10 L−1). Instead, the changes in H2O2 concentration contrasting high- and low-zooplankton incubations appeared to arise from the resulting changes in bacterial activity. The correlation between bacterial abundance and extracellular H2O2 was stronger in some incubations than others (R2 range 0.09 to 0.55), yet high bacterial densities were consistently associated with low H2O2. Nonetheless, the main control on H2O2 concentrations during incubation experiments relative to those in ambient, unenclosed waters was the regulation of incident light. In an open (lidless) mesocosm experiment in Gran Canaria, H2O2 was persistently elevated (2–6-fold) above ambient concentrations; whereas using closed high-density polyethylene mesocosms in Crete, Svalbard and Patagonia H2O2 within incubations was always reduced (median 10 %–90 %) relative to ambient waters.

Description: Submarine groundwater discharge (SGD) into coastal areas is a common global phenomenon and is rapidly gaining scientific interest due to its influence on marine ecology, the coastal sedimentary environment and its potential as a future freshwater resource. We conducted an integrated study of hydroacoustic surveys combined with geochemical porewater and water column investigations at a well‐known groundwater seep site in Eckernförde Bay (Germany). We aim to better constrain the effects of shallow gas and SGD on high frequency multibeam backscatter data and to present acoustic indications for submarine groundwater discharge. Our high‐quality hydroacoustic data reveal hitherto unknown internal structures within the pockmarks in Eckernförde Bay. Using precisely positioned sediment core samples, our hydroacoustic‐geochemical approach can differentiate intra‐pockmark regimes that were formerly assigned to pockmarks of a different nature. We demonstrate that high‐frequency multibeam data, in particular the backscatter signals, can be used to detect shallow free gas in areas of enhanced groundwater advection in muddy sediments. Intriguingly, our data reveal relatively small (typically 〈15 m across) pockmarks within the much larger, previously mapped, pockmarks. The small pockmarks, which we refer to as “intra‐pockmarks”, have formed due to the localized ascent of gas and groundwater; they manifest themselves as a new type of ‘eyed’ pockmarks, revealed by their acoustic backscatter pattern. Our data suggest that, in organic‐rich muddy sediments, morphological lows combined with a strong multibeam backscatter signal can be indicative of free shallow gas and subsequent advective groundwater flow.

Description: A major surface circulation feature of the Arctic Ocean is the Transpolar Drift (TPD), a current that transports river‐influenced shelf water from the Laptev and East Siberian Seas toward the center of the basin and Fram Strait. In 2015, the international GEOTRACES program included a high‐resolution pan‐Arctic survey of carbon, nutrients, and a suite of trace elements and isotopes (TEIs). The cruises bisected the TPD at two locations in the central basin, which were defined by maxima in meteoric water and dissolved organic carbon concentrations that spanned 600 km horizontally and ~25‐50 m vertically. Dissolved TEIs such as Fe, Co, Ni, Cu, Hg, Nd, and Th, which are generally particle‐reactive but can be complexed by organic matter, were observed at concentrations much higher than expected for the open ocean setting. Other trace element concentrations such as Al, V, Ga, and Pb were lower than expected due to scavenging over the productive East Siberian and Laptev shelf seas. Using a combination of radionuclide tracers and ice drift modeling, the transport rate for the core of the TPD was estimated at 0.9 ± 0.4 Sv (106 m3 s‐1). This rate was used to derive the mass flux for TEIs that were enriched in the TPD, revealing the importance of lateral transport in supplying materials beneath the ice to the central Arctic Ocean and potentially to the North Atlantic Ocean via Fram Strait. Continued intensification of the Arctic hydrologic cycle and permafrost degradation will likely lead to an increase in the flux of TEIs into the Arctic Ocean.

Description: Cichlid fishes’ famous diversity in body coloration is accompanied by a highly diverse and complex visual system. Although cichlids possess an unusually high number of seven cone opsin genes, they express only a subset of these during their ontogeny, accounting for their astonishing interspecific variation in visual sensitivities. Much of this diversity is thought to have been shaped by natural selection as cichlids inhabit a variety of habitats with distinct light environments. Also, sexual selection might have contributed to the observed visual diversity, and sexual dimorphism in coloration potentially co‐evolved with sexual dimorphism in opsin expression. We investigated sex‐specific opsin expression of several cichlids from Africa and the Neotropics and collected and integrated datasets on sex‐specific body coloration, species‐specific visual sensitivities, lens transmission and habitat light properties for some of them. We comparatively analyzed this wide range of molecular and ecological data, illustrating how integrative approaches can address specific questions on the factors and mechanisms driving diversification, and the evolution of cichlid vision in particular. We found that both sexes expressed opsins at the same levels ‐ even in sexually dimorphic cichlid species – which argues against coevolution of sexual dichromatism and differences in sex‐specific visual sensitivity. Rather, a combination of environmental light properties and body coloration shaped the diversity in spectral sensitivities among cichlids. We conclude that although cichlids are particularly colorful and diverse and often sexually dimorphic, it would appear that natural rather than sexual selection is a more powerful force driving visual diversity in this hyper‐diverse lineage.

Description: The marine sulphur cycle is driven by the reduction of sulphate to sulphide coupled to microbial decomposition of organic matter. The sulphide produced by sulphate reduction may either react with Fe or organic matter to be buried as pyrite or organic sulphur, respectively; or may be oxidised through different pathways and intermediates. The amount of sulphide that is oxidised in marine sediments is not well constrained, yet oxidative sulphur cycling has critical implications for hypoxic coastal waters and oxygen minimum zones, carbon mineralisation, microbial metabolism and the interpretation of ancient and modern stable isotope signatures. Here, we present an experimental method to directly determine sulphide oxidation rates in undiluted marine sediment incubations. We find that sulphide oxidation rates in the top two centimetres of organic-rich coastal sediments were greater than rates of sulphide production through sulphate reduction and calculate that in the top 6 centimetres, up to 92 % of sulphide produced during sulphate reduction was reoxidised. The rates decreased steeply with depth, however, and sulphide oxidation to sulphate could no longer be quantified 10 cm below the seafloor. Fe oxides were the primary oxidant for sulphide and the sulphide oxidation rate was related to the amount and reactivity of the Fe minerals. These results provide important insights into the magnitude and processes of the sulphur cycle in marine sediments.

Description: Marine food webs form the major component of the biological pump and play a central role in the global carbon (C) cycle. Understanding the response of particular processes in marine food webs to changing environments is a prerequisite to predict changes in ecological functioning in the future ocean. Here, we experimentally assessed the effects of nitrogen:phosphorus (N:P) supply ratios (the molar ratios 10:1, 24:1, and 63:1) on elemental and biochemical quality of marine phytoplankton Rhodomonas sp., and the interactions between food quantity and quality on stoichiometric C:N:P, fatty acids (FAs) and reproductions in copepods Acartia tonsa. Overall, the stoichiometry of A. tonsa was to some extent homeostatic in response to the changing algal C:N and C:P ratios, with significant changes in C:N ratios of A. tonsa observed, especially under higher food quantities. The relative gross growth efficiencies (GGEs) for C and N (and P) were analyzed, revealing that copepods may achieve homeostasis by lowering the GGE for C while increasing it for the limiting nutrient. Egg production rates in A. tonsa were lowest on nutrient deficient diets under low food quantities. Reduced egg production rates may be attributed to the lowered GGEs for C and reduced transfer efficiency of essential FAs between phytoplankton and copepods, indicating interactive-essential effects of elements and FAs on copepod production. Our results highlight that nutrient deficiency in the environments may reduce energy transfer efficiency at the base of food webs by altering phytoplankton chemical composition, which can interact with food quantity and have implications on food web dynamics in the changing ocean.

Description: A comprehensive database of paleoclimate records is needed to place recent warming into the longer-term context of natural climate variability. We present a global compilation of quality-controlled, published, temperature-sensitive proxy records extending back 12,000 years through the Holocene. Data were compiled from 679 sites where time series cover at least 4000 years, are resolved at sub-millennial scale (median spacing of 400 years or finer) and have at least one age control point every 3000 years, with cut-off values slackened in data-sparse regions. The data derive from lake sediment (51%), marine sediment (31%), peat (11%), glacier ice (3%), and other natural archives. The database contains 1319 records, including 157 from the Southern Hemisphere. The multi-proxy database comprises paleotemperature time series based on ecological assemblages, as well as biophysical and geochemical indicators that reflect mean annual or seasonal temperatures, as encoded in the database. This database can be used to reconstruct the spatiotemporal evolution of Holocene temperature at global to regional scales, and is publicly available in Linked Paleo Data (LiPD) format.

Description: Mantle convection is the principal mechanism by which heat is transferred from the deep Earth to the surface. Cold subducting slabs sink into the mantle and steadily warm, whilst upwelling plumes carry heat to the base of lithospheric plates where it can subsequently escape by conduction. Accurate estimation of the total heat carried by these plumes is important for understanding geodynamic processes and Earth's thermal budget. Existing estimates, based upon swell geometries and velocities of overriding plates, yield a global heat flux of ∼2 TW and indicate that plumes play only a minor role in heat transfer. Here, we revisit the Icelandic and Hawaiian plumes to show that their individual flux estimates are likely to be incorrect due to the assumption that buoyancy is mainly produced within the lithosphere and therefore translates at plate velocities. We develop an alternative methodology that depends upon swell volume, is independent of plate velocities, and allows both for decay of buoyancy through time and for differential motion between asthenospheric buoyancy and the overlying plate. Reanalysis of the Icelandic and Hawaiian swells yields buoyancy fluxes of Mg s−1 and Mg s−1, respectively. Both swells are used to calibrate a buoyancy decay timescale of ∼45 Myr for the new volumetric approach, which enables buoyancy fluxes to be estimated for a global inventory of 53 swells. Estimates from magmatic hotspots yield a cumulative lower bound on global plume flux of 2 TW, which increases to 6 TW if amagmatic swells are also included and if all buoyancy is assumed to be thermal in origin. Our results suggest that upwelling plumes play a significant role in the transfer of heat into the uppermost mantle.

Description: Key Points: - The Kamchatka arc lavas show across-arc variations in chalcophile elements, suggesting that the amount of fluid decreases with depth - Slab-derived fluids have a negligible contribution to the Li budget of the Kamchatka arc lavas - CKD lavas have high U/Th, Li/Y, La/Sm and B/Nb ratios, indicating that lawsonite breakdown reaction dominates the water release Chalcophile elements and lithium (Li) isotopes were measured on lavas from a 220 km transect across the Kamchatka arc in order to investigate the fluid variations below arc volcanoes and to trace the geochemical behaviour of Li in convergent plate margins. From the Eastern Volcanic Front (EVF), through the Central Kamchatka Depression (CKD), into the Sredinny Range (SR) volcanic zones, chalcophile element ratios (e.g., As/Ce and Sb/Ce) show clear across‐arc variations, decreasing (e.g., As/Ce: 0.20 to 0.03 and Sb/Ce: 0.013 to 0.002) with increasing depth above the slab (110 to 400 km). This clearly indicates a gradually decreasing influx of slab‐derived fluids added to the mantle wedge as the slab subducts below Kamchatka. In addition, the anomalously high U/Th, La/Sm and B/Nb ratios in the CKD lavas suggest lawsonite breakdown reaction dominates the fluid release in this area. However, Li/Y (0.07 to 1.78) and δ7Li (+1.8 to +5.4‰, with an exception of +8.6‰ in CKD) show limited variations and values similar to the MORB mantle. A dehydration model suggests that slab‐derived fluids, which are characterized by high Li concentration and high δ7Li, do not control the Li budget in Kamchatka arc lavas. Therefore, the isotopic heavy Li from slab‐derived fluids likely equilibrates in the sub‐arc mantle, which acts as a buffer for Li systematics. In addition, based on the Li isotopic signatures of Klyuchevskoy volcano, our study demonstrates insignificant Li isotopic fractionation during mantle melting and subsequent differentiation.

Description: Continental shelves in arid tropical settings present particular challenges to 210Pb-based analysis of sedimentation rates and surface mixing owing to the combination of coarse sediment, deep and year-round bioturbation, and lower atmospheric flux of 210Pb. The modern continental shelf at the northern terminus of the hyper-arid Gulf of Eilat/Aqaba (GOE) receives flood-runoff of siliciclastics, producing a mixed seabed with ~20% carbonate that is dominated by larger benthic foraminifera and mollusks. Focusing analysis on only the fine-fraction of deep-penetrating cores (≥70 cm) from 15 to 40 m water depths yields reliable 210Pb profiles, in contrast to analysis of bulk sediment (graphical abstract). Sedimentation rates increase offshore five-fold, from 0.01–0.04 cm/y in 15 m water depth to 0.21–0.27 cm/y in 30–40 m depths, reflecting offshore redistribution of flood-delivered siliciclastic sediments away from the wadi mouth, a result also supported by an offshore increase in the inventory of excess 210Pb. In contrast, the thickness of the surface mixed layer (SML) decreases from 〉30 cm to ~20 cm with proximity to anthropogenic stressors (channelized flood runoff, historic release of sewage and operation of fish cages), which we attribute to the suppression of macrobenthic burrowers. The rate of sedimentation on the Gulf shelf –away from dynamic bypassing in the 15 m shoreface – is comparable to other tropical carbonate shelves rich in large benthic foraminifera, and is higher than rates documented on the adjacent slope, increasing confidence in this approach to 210Pb analysis using only the fine fraction. Analysis of the fine fraction rather than bulk sediment would be a useful adjustment to 210Pb methodology in any area with scarce fine-grained sediment.

Description: Diverse microbial ecosystems underpin life in the sea. Among these microbes are many unicellular eukaryotes that span the diversity of the eukaryotic tree of life. However, genetic tractability has been limited to a few species, which do not represent eukaryotic diversity or environmentally relevant taxa. Here, we report on the development of genetic tools in a range of protists primarily from marine environments. We present evidence for foreign DNA delivery and expression in 13 species never before transformed and for advancement of tools for eight other species, as well as potential reasons for why transformation of yet another 17 species tested was not achieved. Our resource in genetic manipulation will provide insights into the ancestral eukaryotic lifeforms, general eukaryote cell biology, protein diversification and the evolution of cellular pathways.

Description: New and compiled geochemical, isotopic and geochronological data allow us to propose a new explanation for Paleogene oceanicmagmatic rocks alongtheIran–Iraqborder.These rocks are represented byathick pile(〉1000 m) ofpillow lavas and pelagic sediments and underlying plutonic rocks. These are sometimes argued to represent a Paleogene ophiolite but there are no associated mantle rocks. Integrated zircon U–Pb ages, bulk rock major and trace element and radiogenic isotope data indicate that these rocks are more likely related to forearc rifting due to extreme extension during Late Paleogene time whichalsotriggeredhigh-fluxmagmatismintheUrumieh–DokhtarMagmaticBeltandexhumationofcorecomplexesinIran. These observations are most consistent with formation of the Paleogene oceanic igneous rocks in a 〉220 km long forearc rift zone.

Description: Deep-water volcanoes are emplaced in water depths 〉1.0 km and are widespread along continental margins and in ocean basins. Whilst the external morphology of deep-water volcanoes can be mapped using bathymetric surveys, their internal structure and true volume remain enigmatic. It is thus difficult to determine how deep-water volcanoes grow. We investigate 13 Late Miocene-to-Quaternary, deep-water volcanoes that are imaged in 3D by seismic reflection data from the northern South China Sea, which allow us to quantify their external morphology and examine their internal structure. These deep-water volcanoes were emplaced in water depths 〉1.5 km, are relatively small (〈3.0 km diameter, 〈0.56 km tall, and 〈0.92 km3 in volume), and have steep slopes (up to 42°). Most of the volcanoes have erosional, ‘crater-like’ bases, infilled with sub-horizontal seismic reflections. These crater-like bases are overlain by downward-converging, conical seismic reflections delineating the classical volcano morphology. We suggest the crater-like bases formed by excavation of cold, wet, and poorly consolidated near-seabed sediment during expulsion of hydrothermal fluid, and not by explosive magmatic eruptions or gravitational subsidence. Erupted igneous material infilled the precursor craters with the observed sub-horizontal layers, likely comprising hyaloclastites. After this initial phase of volcanism, the buildup of volcanic material produced layers that are now represented by the flank-parallel or downward-converging, conical seismic reflections. We suggest high hydrostatic pressures of 〉15 MPa, which are typical of water depths 〉1.5 km, inhibited degassing and fragmentation of ascending magma and thus erupted lava. This lack of degassing and fragmentation permitted effusive eruptions during the latter stages of volcanism. Our models for volcano growth in the deep submarine realm demonstrate the power of using 3D seismic data when investigating the internal structure and total volume of deep-water volcanoes.

Description: In the autumn of 2014, nine large mesocosms were deployed in the oligotrophic subtropical North-Atlantic coastal waters off Gran Canaria (Spain). Their deployment was designed to address the acidification effects of CO2 levels from 400 to 1,400 mu atm, on a plankton community experiencing upwelling of nutrient-rich deep water. Among other parameters, chlorophyll a (chl-a), potential respiration (Phi), and biomass in terms of particulate protein (B) were measured in the microplankton community (0.7-50.0 mu m) during an oligotrophic phase (Phase I), a phytoplankton-bloom phase (Phase II), and a post-bloom phase (Phase III). Here, we explore the use of the Phi/chl-a ratio in monitoring shifts in the microplankton community composition and its metabolism. Phi/chl-a values below 2.5 mu L O-2 h(-1) (mu g chl-a)(-1) indicated a community dominated by photoautotrophs. When Phi/chl-a ranged higher, between 2.5 and 7.0 mu L O-2 h(-1) (pg chl-a)(-1) , it indicated a mixed community of phytoplankton, microzooplankton and heterotrophic prokaryotes. When Phi/chl-a rose above 7.0 mu L O-2 h(-1) (mu g chl-a)(-1), it indicated a community where microzooplankton proliferated (〉10.0 mu L O-2 h(-1) (mu g chl-a)(-1)), because heterotrophic dinoflagellates bloomed. The first derivative of B, as a function of time (dB/dt), indicates the rate of protein build-up when positive and the rate of protein loss, when negative. It revealed that the maximum increase in particulate protein (biomass) occurred between 1 and 2 days before the chl-a peak. A day after this peak, the trough revealed the maximum net biomass loss. This analysis did not detect significant changes in particulate protein, neither in Phase I nor in Phase III. Integral analysis of Phi/chl-a and B, over the duration of each phase, for each mesocosm, reflected a positive relationship between 4) and pCO(2) during Phase II [alpha = 230.10-5 mu L O-2 h(-1) L-1 (patm CO2)(-1) (phase-day)(-1), R-2 = 0.30] and between chl-a and pCO(2) during Phase III [alpha = 100.10(-5) Ag chl-a L-1 (mu atmCO(2))(-1) (phase-day)(-1), R-2 = 0.84]. At the end of Phase II, a harmful algal species (HAS), Vicicitus globosus, bloomed in the high pCO(2) mesocosms. In these mesocosms, microzooplankton did not proliferate, and chl-a retention time in the water column increased. In these V globosus-disrupted communities, the (Phi/chl-a ratio [4.1 +/- 1.5 /mu L O-2 h(-1) (mu g chl-a)(-1)] was more similar to the Phi/chl-a ratio in a mixed plankton community than to a photoautotroph-dominated one.

Description: Arctic fjord sediments of Svalbard receive terrestrial material from glacial runoff and organic matter from marine primary productivity. Organic carbon mineralization proceeds primarily through sulfate and iron reduction in the fjord sediment. The ongoing retreat of glaciers in the high Arctic is altering the input of glacial material to the fjords, with unknown consequences for the iron and sulfur cycles in the fjord sediments. We measured sulfate reduction rates in sediment cores and analyzed porewater geochemistry, then compared these results to long-term sediment incubations to determine the rates of iron reduction and sulfide oxidation in three glacially influenced fjords on the west coast of Spitsbergen, Svalbard. Despite an abundance of glacially-sourced Fe(III)-oxide minerals, active sulfate reduction took place throughout the sediment. Analyses of the sulfur and oxygen isotopic composition of porewater sulfate and sulfate concentrations suggest that sulfide produced from biological sulfate reduction is reoxidized to sulfate. Long-term sediment incubations indicated sulfide oxidation at all three stations. The rate of sulfide oxidation was controlled by both the rate of sulfate reduction and the quantity and reactivity of Fe(III)-oxides. In our experimental incubations, we detected a decrease in Fe(III) content of the 0.5 M HCl and ascorbate-extractable fractions, but not in the 6 M HCl fraction, indicating that the highly reactive Fe(III) fraction is utilized by microorganisms and serves as the oxidant for sulfide oxidation. Our results show that sulfide oxidation in glacially-influenced fjord sediments is a wide-spread geochemical process. Further warming will drive glacial retreat onto land, where sediment-laden glacial meltwater will be altered during flow through proglacial streams and lakes before entering the marine environment. Fjord sediments will likely become more sulfidic, as glaciers deliver less particulate, highly-reactive metal oxides to the marine environment.

Description: The fungal genus Pyrenochaetopsis is commonly found in soil, terrestrial, and marine environments, however, has received little attention as a source of bioactive secondary metabolites so far. In a recent work, we reported the isolation and characterization of three new anticancer decalinoyltetramic acid derivatives, pyrenosetins A-C, from the Baltic Fucus vesiculosus-derived endophytic fungus Pyrenochaetopsis sp. FVE-001. Herein we report a new pentacyclic decalinoylspirotetramic acid derivative, pyrenosetin D (1), along with two known decalin derivatives wakodecalines A (2) and B (3) from another endophytic strain Pyrenochaetopsis FVE-087 isolated from the same seaweed and showed anticancer activity in initial screenings. The chemical structures of the purified compounds were elucidated by comprehensive analysis of HR-ESIMS, FT-IR, [a]D, 1D and 2D NMR data coupled with DFT calculations of NMR parameters and optical rotation. Compounds 1-3 were evaluated for their anticancer and toxic potentials against the human malignant melanoma cell line (A-375) and the non-cancerous keratinocyte cell line (HaCaT). Pyrenosetin D (1) showed toxicity towards both A-375 and HaCaT cells with IC50 values of 77.5 and 39.3 μM, respectively, while 2 and 3 were inactive. This is the third chemical study performed on the fungal genus Pyrenochaetopsis and the first report of a pentacyclic decalin ring system from the fungal genus Pyrenochaetopsis.

Description: Habitat heterogeneity and species diversity are often linked. On the deep seafloor, sediment variability and hard-substrate availability influence geographic patterns of species richness and turnover. The assumption of a generally homogeneous, sedimented abyssal seafloor is at odds with the fact that the faunal diversity in some abyssal regions exceeds that of shallow-water environments. Here we show, using a ground-truthed analysis of multibeam sonar data, that the deep seafloor may be much rockier than previously assumed. A combination of bathymetry data, ruggedness, and backscatter from a trans-Atlantic corridor along the Vema Fracture Zone, covering crustal ages from 0 to 100 Ma, show rock exposures occurring at all crustal ages. Extrapolating to the whole Atlantic, over 260,000 km2 of rock habitats potentially occur along Atlantic fracture zones alone, significantly increasing our knowledge about abyssal habitat heterogeneity. This implies that sampling campaigns need to be considerably more sophisticated than at present to capture the full deep-sea habitat heterogeneity and biodiversity.

Description: Highlights • Nd isotope data reflect advection and dilution of Mediterranean Outflow Water on its way north in the Bay of Biscay. • Combined Hf and Nd isotopes are a sensitive indicator of inputs from land as well as long distance advection and mixing. • Nd isotope results of this and earlier studies demonstrate the temporally variable flow path of Mediterranean Sea Water. We present dissolved neodymium and hafnium concentrations and isotope compositions of surface and deep-water masses from the Bay of Biscay. Neodymium isotope signatures in surface waters of the Bay of Biscay are mostly dominated by local weathering inputs from the surrounding continental margin. Subsurface Eastern North Atlantic Central Water (ENACW) shows a distinct Nd isotope signature (εNd ≅ −12) at the southwestern-most station and is significantly diluted by mixing with more radiogenic waters or shifted by inputs of relatively radiogenic particulate Nd on its way north along the European margin. Furthermore, the Nd isotope data clearly show a declining fraction of Mediterranean Sea Water (MSW) at intermediate depths on its way north indicating that only 40% to 60% of MSW still present in the mixture at the Galician margin arrive at the stations further north in the Bay of Biscay. An interannual variability of the flow path of MSW is identified when comparing the results of the Nd isotope compositions and salinity data of this study with those of earlier studies from the area. In agreement with Nd isotope and concentration analyses the Hf isotope composition of MSW is set by large-scale inputs of terrigenous material into the Mediterranean as can be deduced from elevated Hf concentrations still observable at the Galician margin. Hf isotope signatures of all water masses of the Bay of Biscay, moreover, are overprinted by local weathering inputs and do not reflect water mass mixing. However, combined dissolved Nd and Hf isotopes serve as indicators of local weathering influences on signatures expected from long distance water mass mixing.

Description: Communities are shaped by scale dependent processes. To study the diversity and variation of microbial communities across scales, the invasive and widespread seaweed Agarophyton vermiculophyllum presents a unique opportunity. We characterized pro‐ and eukaryotic communities associated with this holobiont across its known distribution range, which stretches over the northern hemisphere. Our data reveal that community composition and diversity in the holobiont vary at local but also larger geographic scales. While processes acting at the local scale (i.e., within population) are the main structuring drivers of associated microbial communities, changes in community composition also depend on processes acting at larger geographic scales. Interestingly, the largest analysed scale (i.e., native and non‐native ranges) explained variation in the prevalence of predicted functional groups, which could suggest a functional shift in microbiota occurred over the course of the invasion process. While high variability in microbiota at the local scale supports A. vermiculophyllum to be a generalist host, we also identified a number of core taxa. These geographically independent holobiont members imply that cointroduction of specific microbiota may have additionally promoted the invasion process.

Description: Highlights: • Feeding overlap was highly expressed between native and non-native oyster. • Differences were recorded in zooplankton but not in phytoplankton consumption. • O. edulis larvae in C. gigas stomach content was confirmed by DNA analysis. • O. edulis had broader isotopic niche than C. gigas. Abstract: In order to detect the possible regulatory effect of non-native C. gigas on the native O. edulis, under aquaculture conditions, feeding interactions between them were investigated in a highly productive environment of Lim Bay (Adriatic Sea). The present study uses a multi-methodological approach, including stomach content, DNA barcoding and stable isotope analysis to elucidate the feeding ecology of two oyster species. The research confirmed a high overlap throughout the year in the feeding traits among native and non-native oyster species. Competition for food was not the only relationship that exists between the investigated species as the presence of O. edulis larvae in C. gigas stomach content was confirmed by DNA analysis. Findings are not in favour of introducing C. gigas to commercial aquaculture in any new areas in the Adriatic Sea and support the need to improve the existing O. edulis aquaculture and conserve its wild stocks.

Description: Highlights • The SUGAR project has developed and tested various methods for gas production from marine gas hydrates from micro to field scale. • Numerical simulations improved the understanding of processes on molecular to reservoir scale. • Depressurization is a promising technology for exploiting gas hydrate deposits in the Danube Delta. • The injection of CO2 or CO2–N2 is not a suitable method for the exploitation of gas hydrate deposits in the Danube Delta. Abstract One important scientific objective of the national research project SUGAR – Submarine Gas Hydrate Reservoirs was the development, improvement, and test of innovative concepts for the production of methane from natural gas hydrate reservoirs. Therefore, different production methods, such as the thermal stimulation using in situ combustion, the chemical stimulation via injection of CO2 as a gaseous, liquid or supercritical phase and depressurization were tested alone or in combination at different scales. In the laboratory experiments these ranged from pore and hydrate grain scale to 425-L reactor volume, whereas numerical models were applied to describe the related processes from molecular to reservoir scale. In addition, the numerical simulations also evaluated the feasibility and efficiency of the application of these methods in selected areas, such as the Danube Paleodelta in the Black Sea, addressing the two dominant methane hydrate reservoir settings, buried channel-levee and turbidite systems. It turned out, that the injection of CO2 or a CO2–N2 gas mixture is not applicable for the Danube Paleodelta in the Black Sea, because the local pressure and temperature conditions are too close to the equilibrium conditions of both, the CO2 hydrate and a CO2–N2 mixed hydrate stability fields. Experiments using thermal stimulation and depressurization showed promising results but also some issues, such as sufficient heat transfer. In summary it can be said that the applicability and efficiency of each method has to be proven for each specific hydrate reservoir conditions. Based on the results obtained by numerical simulations the most promising and safe method for the production of CH4 from hydrate bearing sediments in the Danube Paleodelta would be the depressurization technique. This study summarizes the main experimental and modeling results.