ALBERT

Description: Addressing climate change and reducing greenhouse gas emissions are critical global challenges. As a substantial contributor to emissions, animal-based products are under increasing scrutiny. Animal-free dairy products provide a potential. Although understanding consumer acceptance of these products is crucial, the literature on this topic is scant. This study investigates the perception and acceptance of animal-free dairy among German consumers (N = 1,487) using an online survey with five information treatments (general and topic-specific information about animal-free cheese, gene-modified organisms, animal welfare, environmental concerns, and farmer existence). The acceptance of animal-free dairy was measured by the respondents' willingness to try, substitute, buy, and regularly buy animal-free cheese. Acceptance was found to be comparatively lower than in past studies, although still prevalent among 45.65 % of consumers. Notably, there were significant variances in consumers' perspectives toward animal-free cheese, causing an irregular distribution in their willingness statements. Multi-group analysis using partial least squares structural equation modeling showed that consumer acceptance did not significantly differ between treatment groups. However, individual analysis revealed that the willingness to buy animal-free cheese was positively influenced by perceived benefits and perceived sustainability. Conversely, perceived risks decreased this willingness. Positive attitudes toward farming and knowledge about farming increased perceived risks, while high social trust lowered them. Attitudes toward animal welfare and social trust positively influenced perceived benefits. These findings can be applied to inform and facilitate market introduction strategies of animal-free dairy products for producers and policy makers, providing insights into consumer acceptance of these products in Germany.

Description: The oceans play a major role in moderating atmospheric CO2 levels. Enhanced CO2 uptake into ocean waters can be achieved by the provision of appropriate cations to the surface ocean, an approach known as ocean alkalinity enhancement (OAE). Here, we present a calcium ion battery approach that enhances alkalinity via electrochemical manipulation of seawater calcium concentrations. We demonstrate the efficacy of this approach using a potassium barium iron cyanide [K2BaFe(CN)6] (PBFC) electrode, a Prussian blue analogue, to move calcium ions from one reservoir of seawater to another. Using material and electrochemical characterization of the Ca2+ ion insertion and expulsion properties of PBFC in synthetic seawater, we determine the repeatability of Ca2+ ion insertion and expulsion from the PBFC electrode. Our analyses prove a 2.75 % increase in seawater alkalinity via the PBFC electrode, which yields 2.64 mg CO2 (0.72 mg C) uptake per liter of seawater. This proof-of-concept method offers a unique, low-cost, energy efficient electrochemical approach for atmospheric carbon dioxide removal that can combine with marine-based renewable energy to enable a new family of effective, scalable climate change solutions.

Description: Seismic data represent one of the most valuable resources for investigating the internal structure and composition of the earth. One of the first people to deduce earth structure from seismic records was Mohorovičić, a Serbian seismologist who, in 1909, observed two distinct traveltime curves from a regional earthquake. He determined that one curve corresponded to a direct crustal phase and the other to a wave refracted by a discontinuity in elastic properties between crust and upper mantle. This worldwide discontinuity is now known as the Mohorovičić discontinuity or Moho for short. On a larger scale, the method of Herglotz and Wiechart (see, for example, Gubbins, 1992) was first implemented in 1910 to construct a 1-D whole earth model. The method uses the relationship between angular distance and ray parameter to determine velocity as a function of radius within the earth.

Description: Over the past 50 years, our understanding of the role of trace elements in animals and humans has significantly expanded. Some elements have been recognized as essential for vital body functions. Since the 1950s, with advances in histochemical and spectrometric methods, the distribution of trace elements in different structures of the brain has been studied. Scientific knowledge about the effects of trace elements on brain function has accumulated tremendously as well. Essential trace elements are considered as micronutrients, which are not produced in the body and mainly come from food. Different brain regions such as the cortex, white matter, basal ganglia, and the limbic system have various developmental trajectories and the so-called “critical periods.” The correctness of development is determined by the course of various processes (proliferation, migration, myelination, differentiation, etc.). Thus, it could be assumed that an imbalance of essential trace elements in critical periods of brain maturation can lead to detrimental morphofunctional consequences and impaired brain development. In this chapter, we have reviewed the most studied trace elements that are involved in neurogenesis, such as Fe, Zn, I, Se, Cu, and Mn, and their possible contribution to the manifestation of neurological disorders.

Description: Sponges are ecologically important benthic organisms with many important functional roles. However, despite increasing global interest in the functions that sponges perform, there has been limited focus on how such functions will be impacted by different anthropogenic stressors. In this review, we describe the progress that has been made in our understanding of the functional roles of sponges over the last 15 years and consider the impacts of anthropogenic stressors on these roles. We split sponge functional roles into interactions with the water column and associations with other organisms. We found evidence for an increasing focus on functional roles among sponge-focused research articles, with our understanding of sponge-mediated nutrient cycling increasing substantially in recent years. From the information available, many anthropogenic stressors have the potential to negatively impact sponge pumping, and therefore have the potential to cause ecosystem level impacts. While our understanding of the importance of sponges has increased in the last 15 years, much more experimental work is required to fully understand how sponges will contribute to reef ecosystem function in future changing oceans.

Description: Spatially variable basal conditions are thought to govern how ice sheets behave at glacial time scales (〉1000 years) and responsible for changes in dynamics between the core and peripheral regions of the Laurentide and Fennoscandian ice sheets. Basal motion is accomplished via the deformation of unconsolidated sediments, or via sliding of the ice over an undeformable bed. We present an ice sheet sliding module for the Parallel Ice Sheet Model (PISM) that takes into account changes in sediment cover and incorporates surface meltwater. This model routes meltwater, produced at the surface and base of the ice sheet, toward the margin of the ice sheet. Basal sliding is accomplished through the deformation of water saturated sediments, or sliding at the ice-bed interface. In areas with continuous, water saturated sediments, sliding is almost always accomplished through sediment deformation. In areas with incomplete cover, sliding has a stronger dependence on the supply of water. We find that the addition of surface meltwater to the base is a more important factor for ice sheet evolution than the style of sliding. In a glacial cycle simulation, our model causes a more rapid buildup of the Laurentide Ice Sheet.

Description: This literature review presents major environmental indicators and their optimum variation ranges for the prevalence of Vibrio parahaemolyticus in the marine environment by critically reviewing and statistically analyzing more than one hundred studies from countries around the world. Results of this review indicated that the prevalence of Vibrio parahaemolyticus in the marine environment is primarily responsive to favorable environmental conditions that are described with environmental indicators. The importance of environmental indicators to the prevalence of Vibrio parahaemolyticus can be ranked from the highest to lowest as Sea Surface Temperature (SST), salinity, pH, chlorophyll a, and turbidity, respectively. It was also found in this study that each environmental indicator has an optimum variation range favoring the prevalence of Vibrio parahaemolyticus. Specifically, the SST range of 25.67 ± 2 °C, salinity range of 27.87 ± 3 ppt, and pH range of 7.96 ± 0.1 were found to be the optimum conditions for the prevalence of Vibrio parahaemolyticus. High vibrio concentrations were also observed in water samples with the chlorophyll a range of 16–25 μg/L. The findings provide new insights into the importance of environmental indicators and their optimum ranges, explaining not only the existence of both positive and negative associations reported in the literature but also the dynamic associations between the Vibrio presence and its environmental drivers.

Description: The present worldwide study of 31 off-shore back-arc basins and subbasins (BABs) identifies their principal characteristics based on a broad spectrum of geophysical and subduction-related parameters. This synthesis is next used to identify trends in evolution of the back-arc basins for improving our understanding of subduction systems in general. The analysis, based on the present plate configuration, demonstrates that geophysical characteristics and fate of the back-arc basins are essentially controlled by the nature of the overriding plate, which controls lithosphere thermo-compositional structure and rheology. The plate nature governs the length of the extensional zone in back-arc settings along the trench, the efficiency of lithosphere stretching, BAB crustal structure, its buoyancy and bathymetry. Subduction dip angle apparently controls the location of slab melting zone and the efficiency of slab roll-back with feedback link to other parameters. By tectonic nature of the overriding plate (the downgoing plate is always oceanic) the back-arc basins are split into active BABs formed by ocean-ocean, arc-ocean, and continent-ocean convergence, and extinct back-arc basins. By geophysical characteristics, BABs formed on continental plates are subdivided into active BABs with and without seafloor spreading, and extinct BABs are subdivided to Pacific, possibly formed on oceanic plates, and non-Pacific with reworked continental or arc fragments. Six types of BABs are distinctly different. Extension of the overriding oceanic plate above a steeply dipping old oceanic plate, preferentially subducting nearly westwards, forms large deep back-arc basins with a thin oceanic-type crust. In contrast, BABs on the overriding continental or arc plates form at small opening rates and often by shallow subduction of younger oceanic plates with random subduction orientation; these BABs have small size, shallow bathymetry, and hyperextended or transitional ~20 km thick arc- or continental-type crust typical of passive margins. The presence of a 2–5 km thick high-Vp lowermost crustal layer, characteristic of BABs in all settings, indicates the importance of magmatic underplating in their crustal growth. Conditions required for the initiation of a back-arc basin and transition from stretching to seafloor opening depend on the nature of the overriding plate. BABs formed on oceanic plates always evolve to seafloor spreading. BABs formed on continental or arc plates require a long spreading duration with large (〉8 cm/y) opening rates and crustal thinning factor 2.8–5.0 to progress from crustal extension to seafloor spreading; such transition does not happen in back-arc basins formed behind a shallow subduction (〈45o) of a young (〈40 My) oceanic plate. The nature of the overriding plate also determines the fate of back-arc basins after termination of lithosphere extension: extinct Pacific back-arc basins with oceanic-type crust evolve towards deep old “normal” oceans, while shallow non-Pacific BABs with low heat flow and thick crust are likely to preserve their continental or arc affinity. BABs do not follow oceanic cooling plate model predictions. Distinctly different geophysical signatures for spreading at mid-ocean ridges and for back-arc seafloor spreading are caused by a principally different nature of their dynamics.

Description: Highlights • The hydrothermal fluids were sampled from a neovolcanic ridge within a non-transform offset. • Serpentinization has been involved on the pathway of hydrothermal circulation • The fluids are strongly affected by phase separation with extremely high Cl content in brine phase • A hybrid model of hydrothermal circulation controlled by tectonic and magmatic activities simultaneously was proposed. The Daxi Vent Field (DVF) is located on a neovolcanic ridge within a non-transform offset at water depths of ∼3500 m, on the Carlsberg Ridge, northwest Indian Ocean. In 2017, we investigated this site using the submersible Jiaolong and collected two fluid samples from orifices of chimneys named “Buddha's Hands” and “A1”, about 37 m apart. Their in-situ measured temperatures are 273 °C and 272 °C, respectively. The Buddha's Hands fluid is highly Cl-enriched (928 mM), while the A1 fluid is Cl-depleted (303 mM). This indicates that they have undergone phase separation. The segregated phases must have remixed during the ascent because the vapor and brine phases sampled cannot be produced by the same phase separation history without other processes. Olivine-rich and/or ultramafic mantle rocks must have been involved during the hydrothermal circulation as evidenced by high dissolved H2 (7.07 mM) and methane (0.884 mM) concentrations, a depletion in B relative to seawater, high Ca and low K, and large positive Eu anomalies. The Fe content in Buddha's Hands fluid is extremely high (11,900 μM) as a result of phase separation, while the Cu concentrations in both fluids are relatively low due to entrainment of seawater which results in precipitation of Cu-rich sulfides in the subseafloor. The concentrations of Zn, Ag, Ga, Sn, Sb, and Cd in A1 vent fluid are significantly elevated due to generation of acidity and remobilization of these elements as Cu-rich sulfides are deposited. The subseafloor processes and associated geochemistry of hydrothermal fluids at the DVF are distinct from other mid-ocean ridge hydrothermal systems due to the specific geologic setting. Hence a hybrid model of hydrothermal circulation is proposed. This study broadens our understanding of the hydrothermal processes occurring in areas of NTO setting and provides more information on mass fluxes discharging from hydrothermal systems and the formation of sulfide deposits.

Description: Since the 1980s, the Common Fisheries Policy (CFP) has shaped European fisheries. It has often been criticised for being too prescriptive and, above all, for failing to protect either fishermen or ecosystems. The last reform dates back to the early 2010 s and has led to a slight but slow improvement in the state of ecosystems. Given that the CFP is in the process of evaluation, a group of French fishery scientists set up an initiative to add to the debate on what should be retained, reinforced or added to a possible new reform. This initiative came 10 years after a previous manifesto that presented their vision for fisheries in Europe. Four major issues emerged from the current initiative: (1) a need for transparency and simplification in fisheries management, (2) a need for more consultation and dialogue between stakeholders, (3) the urgency of the situation in the Mediterranean Sea, and (4) the necessity of putting into practice all research developments for an ecosystem approach to fisheries. Compared to 10 years ago, the response of scientists shows that the focus is no longer on achieving the maximum sustainable yield, but rather on the following steps to protect ecosystems and fisheries. An ecosystem approach to fisheries remains indispensable for both ecosystems and fishing activities. To this end, scientists put forward numerous proposals to improve the CFP, acknowledging that the final solutions should emerge from consultation with stakeholders. Climate change, an issue raised much more than in the manifest, reinforces the need to act.

Description: Highlights: • Trematodes can affect gastropods' biochemical condition and grazing rates • L. littorea fed more on invasive G. vermiculophylla than on native F. vesiculosus • Trematode-infected snails fed on average 18 % more than uninfected snails • An increase in temperature induced the mobilization of energy reserves • Trematode-induced glycogen decrease might reduce gastropod heat stress tolerance Abstract: Marine bioinvasions are of increasing attention due to their potential of causing ecological and economic loss. The seaweed Gracilaria vermiculophylla has recently invaded the Baltic Sea, where, under certain conditions, it was found to outcompete the native alga Fucus vesiculosus. Parasites of grazers and temperature are among the potential factors which might indirectly modulate the interactions between these co-occurring algae through their single and combined effects on grazing rates. We tested the temperature and parasitism effects on the feeding of the gastropod Littorina littorea on F. vesiculosus vs. G. vermiculophylla. Uninfected and trematode-infected gastropods were exposed to 10, 16, 22, and 28 center dot C for 4 days while fed with either algae. Faeces production was determined as a proxy for grazing rate, and HSP70 expression, glycogen and lipid concentrations were used to assess the gastropod's biochemical condition. Gracilaria vermiculophylla was grazed more than F. vesiculosus. Trematode infection significantly enhanced faeces production, decreased glycogen concentrations, and increased lipid concentrations in the gastropod. Warming significantly affected glycogen and lipid concentrations, with glycogen peaking at 16 center dot C and lipids at 22 center dot C. Although not significant, warming and trematode infection increased HSP70 levels. Increased faeces production in infected snails and higher faeces production by L. littorea fed with G. vermiculophylla compared to those which fed on F. vesiculosus, suggest parasitism as an important indirect modulator of the interaction between these algae. The changes in the gastropod's biochemical condition indicate that thermal stress induced the mobilization of energy reserves, suggesting a possible onset of compensatory metabolism. Finally, glycogen decrease in infected snails compared to uninfected ones might make them more susceptible to thermal stress.

Description: Highlights: • Higher representation of picophytoplankton in land-terminating glacier fjord. • Smaller phytoplankton cells associated with glacial retreat. • Intermediate baroclinic circulation influences phytoplankton distribution. • Glacial retreat likely to have major implications for summer productivity. Abstract: Along Greenland's coastline, the magnitude and timing of primary production in fjords is influenced by meltwater release from marine-terminating glaciers. How local ecosystems will adapt as these glaciers retreat onto land, forcing fundamental changes in hydrography, remains an open question. To further our understanding of this transition, we examine how marine- and land-terminating glaciers respectively influence fjord bloom phenology. Between spring and autumn 2019, we conducted along-fjord transects of hydrographic variables, biogeochemical properties and pico- and nanophytoplankton counts to illustrate the contrasting seasonal bloom dynamics in the fjords Nuup Kangerlua and Ameralik. These fjords are in the same climatic region of west Greenland but influenced by different glacial structures. Nuup Kangerlua, a predominantly marine-terminating system, was differentiated by its sustained second summer bloom and high Chl a fluorescence in summer and autumn. In Ameralik, influenced by a land-terminating glacier, we found higher abundances of pico- and nanophytoplankton, and high cyanobacteria growth in autumn. The summer bloom in Nuup Kangerlua is known to be coincident with subglacial freshwater discharge sustaining renewed nutrient supply to the fjord. We observe here that the intermediate baroclinic circulation, which creates an inflow at subsurface depths, also plays an important role in increasing nutrient availability at shallower depths and potentially explains the distribution of primary producers. Our observations suggest that the retreat of marine-terminating glaciers onto land, with consequent increases in surface water temperature and stratification, and reduced light availability, may alter the magnitude, composition, and distribution of summer productivity.

Description: Highlights: • Networks indicators reveal structure of the food webs depicted by ecosystem models. • Fishing mortality affects the structure and functioning of the food webs. • Increasing fishing mortality of all fish groups triggers strong indicator response. • Overfishing endangers ecosystem resilience. Marine ecosystems are exposed to multiple stressors, mainly fisheries that, whenever mismanaged, may cause irreversible damages to whole food webs. Ecosystem models have been applied to forecast fisheries impact on fish stocks and marine food webs. These impacts have been studied through the use of multiple indicators that help to understand ecosystem responses to stressors. This study focused on a category of ecological indicators derived from the network theory to quantify energy flows inside the food web. These indicators were computed using two ecosystem models applied to the Eastern English Channel (i.e. Atlantis and OSMOSE). This work aimed at investigating how several ecological network indicators respond to different levels of fishing pressure and evaluating their robustness to model structure and fishing strategies. We applied a gradient of fishing mortality using two ecosystem models and carried out ecological network analysis to obtain network-derived indicators. The results revealed that the indicators response is highly driven by the food web structure, although the model assumptions buffered some results. The indicators computed from OSMOSE outputs were more sensitive to changes in fishing pressure than those from Atlantis. However, once the food web from Atlantis was simplified to mimic the structure of OSMOSE model, the indicators of the modified Atlantis became more sensitive to the intensity of fishing pressure. The indicators related to amount of energy flow and to the organization of the flows in the food web were sensitive to the increase of fishing mortality for all fishing strategies. These indicators suggested that increasing fishing mortality jeopardizes the amount of energy mobilized by the food webs and simplifies the ecological interactions, which has implications for the resilience of marine ecosystems. The study shed light on the trophic networks structure and functioning of the ecosystems whenever exposed to distur-bances. Furthermore, these indicators might be adequate for whole ecosystem assessments of health and contribute to ecosystem management.

Description: Highlights • Oceanic nutrient supply from seabird guano is poorly constrained by field observations. • This was assessed for guano from caught-and-released North Atlantic seabirds. • Guano released nutrients and relieved in situ phytoplankton nutrient limitation. • Guano was modelled to potentially be a major nutrient supply term in summer. • Declining pelagic seabird populations will impact this function. Abstract Nutrients supplied via seabird guano increase primary production in some coastal ecosystems. A similar process may occur in the open ocean. To investigate this directly, we first measured bulk and leachable nutrient concentrations in guano sampled in the North Atlantic. We found that guano was strongly enriched in phosphorus, which was released as phosphate in solution. Nitrogen release was dominated by reduced forms (ammonium and urea) whilst release of nitrate was relatively low. A range of trace elements, including the micronutrient iron, were released. Using in-situ bioassays, we then showed that supply of fresh guano to ambient seawater increases phytoplankton biomass and photochemical efficiencies. Based on these results, modelled seabird distributions, and known defecation rates, we estimate that on annual scales guano is a minor source of nutrients for the surface North Atlantic. However, on shorter timescales in late spring/summer it could be much more important: Estimates of upper-level depositions of phosphorus by seabirds were three orders of magnitude higher than modelled aerosol deposition and comparable to diffusion from deeper waters.

Description: Precipitation chemistry data provide important information for environmental studies on large-scale element cycling and anthropogenic impacts on our atmosphere, but also for hydrochemical models and groundwater recharge estimations via the Chloride Mass Balance method. Such recharge data play a crucial role in groundwater management, particularly in (semi-)arid areas. Unfortunately, precipitation analyses are often scarce in such regions. This also applies to the Arabian Peninsula, including southern Oman. To overcome this lack of rain chemistry data, we developed a strategy for automatic weekly bulk precipitation sampling, using recently designed automatic rainwater samplers. The integral samples were gathered along an elevation gradient from the Salalah coast to the Dhofar mountains during the Indian Ocean Monsoon seasons 2017 and 2018. Our major ion analyses of the rainwater samples revealed considerable temporal and spatial heterogeneity, in terms of ion proportions and absolute concentrations. Samples from the coast were relatively salty (EC mostly 〉3000 μS cm−1) and rich in Na+ and Cl−, reflecting small rain amounts and a sea spray effect. Further inland, solute concentrations were lower, partly due to more precipitation, and ions such as Ca2+ and SO42− gained importance, probably due to calcite and gypsum dust. This pattern reflects the interplay between solute availability (influenced by regional geology, wind direction at different altitudes, and wind speed) and precipitation amounts. Cl−/Br− ratios were fairly uniform and scattered around the seawater value. Combining ion concentrations and rain amounts yielded bulk depositions that showed an erratic pattern along the elevation gradient, i.e., depositions did not decrease steadily in inland direction, as one may assume. This suggests that the occasionally reported approach of collecting a few opportunistic grab samples at a single site is unlikely to yield data that are representative for a larger coastal study area.

Description: Cold-water corals (CWCs) are considered vulnerable to environmental changes. However, previous studies have focused on adult CWCs and mainly investigated the short-term effects of single stressors. So far, the effects of environmental changes on different CWC life stages are unknown, both for single and multiple stressors and over long time periods. Therefore, we conducted a six-month aquarium experiment with three life stages of Caryophyllia huinayensis to study their physiological response (survival, somatic growth, calcification and respiration) to the interactive effects of aragonite saturation (0.8 and 2.5), temperature (11 and 15 °C) and food availability (8 and 87 μg C L−1). The response clearly differed between life stages and measured traits. Elevated temperature and reduced feeding had the greatest effects, pushing the corals to their physiological limits. Highest mortality was observed in adult corals, while calcification rates decreased the most in juveniles. We observed a three-month delay in response, presumably because energy reserves declined, suggesting that short-term experiments overestimate coral resilience. Elevated summer temperatures and reduced food supply are likely to have the greatest impact on live CWCs in the future, leading to reduced coral growth and population shifts due to delayed juvenile maturation and high adult mortality.

Description: Marine ecosystem dynamics in the context of climate change is a growing scientific, political and social concern requiring regular monitoring through appropriate observational technologies and studies. Thus, a wide range of tools comprising chemical, biogeochemical, physical, and biological sensors, as well as other platforms exists for marine monitoring. However, their high acquisition and maintenance costs are often a major obstacle, especially in low-income developing countries. We designed an advanced low-cost synoptic marine ecosystem observation system that operates at relatively high temporal frequencies, named PlasPi TDM. This instrument is an improved version of the camera system (PlasPI marine cameras) developed in 2020 by Autun Purser from the Alfred Wegener Institute Helmholtz Center for Polar and Marine Research (Germany), and collaborators. It incorporates several innovative developments such as multispectral (records the spectrum of any object photographed), temperature and pressure sensors. The PlasPi TDM operates to a depth of 200 m. The various field deployments demonstrate the operational capability of the PlasPi TDM for different applications and illustrate its considerable potential for in-situ observations and marine surveillance in Africa. This device is intended as an open-source project and its continued development is encouraged for a more integrated, sustainable and low-cost ocean observing system.

Description: Potential temporal and causal connections among various geologic events have long been discussed in the geological literature. More recently, signs of common periodicities in these episodes have been reported. In this study of correlation and cyclicity of geologic occurrences, we review and synthesize previous work, and utilize the newest data for various major events over the the last 260 My. These include, 1) high-quality radio-isotopic age determinations (U-Pb zircon and 40Ar/39Ar) for continental flood-basalt (CFB) eruptions; 2) the dates of widespread intervals of ocean anoxia; 3) the latest published dates of marine and non-marine extinction events, 4) hyper-thermal climate intervals and 5) the occurrences of stratigraphic Hg anomalies, and non-radiogenic Os-isotope anomalies as potential proxies for large-scale basaltic volcanism. Times of at least 13 of 17 intervals of anoxic oceans are marked by stratigraphic Hg-anomalies, pointing to contemporaneous LIP eruptions, and 5 anoxic intervals in the warm Cretaceous Period are correlated with marine Os-isotope ratios suggesting potential LIP hydrothermal activity. Nine of the ocean-anoxic intervals are thus far correlated with times of marine-extinction episodes, and 8 of those anoxia/extinction co-events are significantly correlated with the ages of the well-dated CFB eruptions. Seven of the marine-extinction events and associated CFB volcanism are coeval with extinctions of non-marine vertebrates, supporting global catastrophic volcano-climatic episodes devastating both marine and terrestrial environments. New digital circular spectral analyses revealed significant underlying cycles of ∼32.5 My and ∼ 26.2 My in the ages of the anoxic events and marine extinctions. Spectral analysis of the latest high-quality ages of the CFBs resulted in similar significant periodicities of 32.8 My and 12.9 My (∼26.2/2 My harmonic). High-frequency periods at various harmonics appear at ∼6.4 My, 8.4 My and 9.7 My in each of the three spectra. These findings support a multi-factor extinction scenario in which release of massive amounts of CO2 and perhaps CH4 mostly from CFB magmas (and in some cases sub-volcanic intrusions into carbon-rich deposits), led to very warm climate intervals with near-lethal to lethal hyper-thermal conditions on land and in the sea. Concurrent release of halogens from CFB eruptions could also have decimated the global ozone layer. In many cases, the warm oceans became acidic, and developed anoxic to euxinic conditions, even up to the ocean surface, contributing to the causes of the marine extinctions. Additionally, four extinction events (late Eocene, end-Cretaceous, end-Jurassic and mid-Norian) correlate closely with the ages of the 4 largest impacts (craters ≥100 km in diameter) over the same period, capable of producing severe climatic effects and extinctions. The potential dominant underlying ∼33-My and 26-My cycles, reported in these and other correlated tectonic, climatic, and biotic events over the last 260 My and beyond, are likely related to the Earth's tectonic-volcanic rhythms, but the similarities with known Milankovitch Earth orbital periods and their amplitude modulations, and with known Galactic cycles, suggest that, contrary to conventional wisdom, the geological events and cycles may be paced by astronomical factors.

Description: We analyse reflection seismic profiles across the outer accretionary wedge at the convergent New Zealand Hikurangi margin. We identify several, in some case stacked, bottom simulating reflections (BSRs). We interpret these multiple BSRs to record changes in gas hydrate stability. With the aid of gas hydrate systems modelling, we identify two geological drivers that affect gas hydrate stability: (1.) rapid sedimentation in trough basins and (2.) uplift and erosion of thrust ridges. Rapid sedimentation in trough basins buries gas hydrates that formed above the former base of gas hydrate stability (BGHS). Locally, we observe a remnant BSR from this process, likely due to residual gas and possibly gas hydrate. The combined effects of uplift and erosion, in contrast, result in the preservation of a remnant BSR within the gas hydrate stability zone, whilst a new BSR forms locally at the present-day BGHS. However, the limited occurrence of double BSRs in seismic data and the model both suggest that the formation of a deeper BSR is limited by gas supply. Formation of significant gas hydrate at this deeper level only occurs in areas of focused gas migration. This slow formation of gas hydrate also has implications for the response to glacio-eustatic sea-level rise: gas hydrates are more likely to accumulate above the BGHS corresponding to the last glacial maximum, whereas only small amounts formed above the deeper present-day BGHS. Hence, future bottom water warming will, at least initially, not lead to significant methane release from dissociating gas hydrates in deep water.

Description: The heterogenous magma supply at ultraslow spreading ridges creates diverse seafloor morphologies and lithospheric structures, which in turn generate a large variability in marine magnetic anomalies. The variability brings difficulties to interpret the evolution of oceanic lithosphere. On the other hand, different magnetic signatures of different seafloors provide an opportunity to identify the modes of seafloor spreading on the ultraslow spreading ridges. Here, we modeled several across-axis magnetic profiles selected from the Gakkel Ridge, Southwest Indian Ridge and Mid-Cayman Spreading Center to explore the lithospheric structure and seafloor spreading processes. Considering conjugate flanks, we observed three modes of seafloor spreading, Magmatic vs Magmatic, Magmatic vs Tectonic, and Tectonic vs Tectonic, on the three ultraslow spreading ridges. These three spreading modes reflect a strong, intermediate, and starved magma supply, respectively. Furthermore, four alternances of the different spreading modes were identified including the Magmatic vs Magmatic to Magmatic vs Tectonic, Magmatic vs Tectonic to Tectonic vs Magmatic, Tectonic vs Tectonic to Magmatic vs Magmatic, and Mixed. These alternances of spreading modes in across-axis direction suggest oscillations of the magma supply at different levels. Variation in the modes of seafloor spreading on four nearby profiles over the Mid-Cayman Spreading Center reveals the evolution of magma supply along the axis of this short ridge.

Description: Farming on hillslopes often affects the accumulation and loss of soil organic matter (SOM) depending on slope position and cropping patterns. Most hillslope studies focus on soil movement to characterize SOM turnover under erosive conditions. In this study, we trace erosion and characterize agronomic practices erosive impacts on SOM translocation and transformation along geomorphic positions. To achieve this, we assessed the horizontal distribution (upper 15 cm) and vertical distribution (to 100 cm profiles) of soil δ15N and δ13C isotope abundance individually. We mapped the spatial distribution of δ13C, δ15N, and SOM turnover indices as a novel approach to tracing erosion and degradation of SOM in the field. Except for tillage (conventional vs. reduced tillage), other individual agricultural practices (residue removal with no cover crop vs. retaining residuals, cover cropping, and fertilizer 0, 40, and 80 kg ha-1 nitrogen) caused no significant shifts in δ15N and δ13C values in topsoil (0–15 cm). Among the evaluated factors, topography and depth predicted soil δ15N and δ13C profiles. Trends in δ13C vs. δ15N showed a wider range of δ13C values in topsoil of upslope plots under reduced tillage, while in the depositional location, conventional tillage had the same effect. This suggests erosion under reduced tillage occurred. Erosion and accelerated decomposition gradually slowed δ13C enrichment with soil depth. Digital soil mapping approach depicted low continuity of δ13C vs. high continuity of δ15N with geomorphic position We attributed the intermediate δ13C values, and steeper slope of δ13C against logarithm of soil organic carbon (SOC) across the slope to erosion and high SOM turnover, particularly of recently added plant inputs. Current results support the prediction of intensive vs. conservation practices’ effects on upslope soil stability and the fate of SOM in both topsoil and at depth of sloping farmlands.

Description: Highlights • Closure of the Tethyan Seaway led to precipitation increase in South Asia but decrease in North Africa. • Closure of the Tethyan Seaway led to enhanced moisture transport from North Africa to South Asia. • Global cooling led to precipitation decrease in North Africa and South Asia during the MMCT. Abstract The Middle Miocene was a period of prominent climatic change, marked by the Mid-Miocene Climatic Optimum (MMCO) and the subsequent global cooling due to a decline of the atmospheric CO2 concentrations (pCO2). In addition to this, the closure of the Tethyan Seaway driven by the Arab-Eurasia collision also had an important effect on the paleoclimatic changes during this period. In this study, we use the Community Earth System Model 1.2.2 (CESM 1.2.2) to simulate the effects of global cooling (i.e. pCO2 decline) and the closure of the Tethyan Seaway on the North African and South Asian climates. Our results show that the global cooling led to a precipitation decrease over both North Africa and South Asia, whereas the closure of the Tethyan Seaway resulted in a precipitation decrease over North Africa but an increase over South Asia. The opposite effects over North Africa and South Asia are due to an increased moisture transport from North Africa to South Asia induced by stronger summer atmospheric circulation when the Tethyan Seaway is closed. We further show that the reconstructed records of drying conditions over North Africa during the warming period from the late Early Miocene to the early Middle Miocene from previous studies can be partly explained by the narrowing of the Tethyan Seaway and its climatic continuing deterioration due to the subsequent final closure and global cooling. Both are precursory conditions for the formation of the Sahara desert. The stronger South Asian monsoon during the Middle Miocene transient cooling period found in previous studies can be partially attributed to the final closure of the Tethyan Seaway.

Description: The beginning of the Mid-Pleistocene Transition (MPT) ~920 ka BP marked the expansion of northern hemisphere ice shields and caused a significant climate change in NW Europe. The MPT ended with the establishment of the 100 kyr ice age cyclicity at ~640 ka BP, due to orbital eccentricity changes. Previous studies explained the northern hemisphere cooling by cooling of sea-surface temperatures, increased sea-ice cover and/or changes in the Atlantic Meridional Overturning Circulation (AMOC) strength. We here discuss very-high resolution parametric echosounder (Parasound) imagery and sediment core analytics from a plastered drift at the eastern Campeche Bank (southern Gulf of Mexico), which was deposited under the influence of the Loop Current (LC). The LC transports warm tropical waters from the Caribbean into the Gulf via the Yucatan Channel. It is a key component of the Gulf Stream system, driving the ocean heat, salinity, and moisture transport towards the N Atlantic. The joint interpretation of reflection patterns, age constraints from color-scanning, foraminiferal stable oxygen isotopes, Sr isotope ratios (87Sr/86Sr) and core-seismic integration led to consistent conclusions about changes in LC strength across the MPT, thereby modulating the deep base level and the deposition of the plastered drift. The development of offlapping or onlapping plastered drifts, or the transition between the two termination patterns is best explained by changes in the depth of the relative deep base level and interpreted by changes in the flow regime.Initially, the Middle Miocene to Pliocene closure of the Central American Seaway caused the onset and intensification of the LC and hence a deep base level fall. The sedimentary deposits from this phase have an offlapping prograding clinoform configuration, resembling a forced regression systems tract as is known from shelf areas. The deep base level fall caused sediment truncation above 500 m present day water depth. Below 500-550 m, the offlapping succession is overlain by sigmoidal and onlapping, transgressive systems tract like clinoforms. The transition from deep base level fall prior to the MPT to deep base level rise documents the weakening of the LC during the early MPT. After the MPT, the LC continued to weaken. The related reduction of heat transport from the Western Atlantic Warm Water Pool into the North Atlantic contributes to the further cooling of the northern hemisphere. Generally, the development of offlapping or onlapping plastered drifts or the transition between the two termination patterns can be explained by changes in the depth of the relative deep base level and interpreted by changes in the flow regime.

Description: Highlights: - Microbiota manipulation has been used to improve the health and performance of several eukaryotes (e.g., humans, agricultural plants, and aquaculture animals), yet until recently remained unexplored for seaweeds. - Seaweed cultivation is the largest aquaculture industry by volume and is rapidly expanding. Technological innovations are needed to improve productivity and meet future global demands. - Bacteria are known to promote growth, assist reproduction, and improve disease resistance in seaweeds. - Knowledge of seaweed–bacterial symbioses has recently been applied to manipulate host microbiota with demonstrated benefits to seaweeds at the laboratory scale. This provides a realistic and practical opportunity to use these at the scale required for seaweed aquaculture and environmental restoration. Eukaryotic hosts are associated with microbial communities that are critical to their function. Microbiota manipulation using beneficial microorganisms, for example, in the form of animal probiotics or plant growth-promoting microorganisms (PGPMs), can enhance host performance and health. Recently, seaweed beneficial microorganisms (SBMs) have been identified that promote the growth and development and/or improve disease resistance of seaweeds. This knowledge coincides with global initiatives seeking to expand and intensify seaweed aquaculture. Here, we provide a pathway with the potential to improve commercial cultivation of seaweeds through microbiota manipulation, highlighting that seaweed restoration practices can also benefit from further understanding SBMs and their modes of action. The challenges and opportunities of different approaches to identify and apply SBMs to seaweed aquaculture are discussed.

Description: The economics of biodiversity is gaining traction and with it the economic valuation of ecosystem services (ESS). Most current developments neglect microbial diversity, although microbial communities provide ecosystem services of great importance. Here we argue that microbial biodiversity (hereafter microbiodiversity) translates into considerable economic value which is usually not explicitly included in quantitative valuation of ecological functions to date. This omission may result in inaccurate values, potentially entailing substantial economic losses, both in private and in public decision-making, due to external effects that arise as microbiodiversity is horizontally and vertically transferred between hosts and natural environments. Microbiodiversity, an important part of biodiversity in general, occupies an irreplaceable position as a natural resource in ecosystems, because of option values derived from the evolutionary potential of microbes, especially if host-associated, and also because of their additional insurance value within changing environments. We illustrate our arguments with specific examples (microbiomes associated with humans, soil, and corals), all of which are jeopardized through anthropogenic pressure. We conclude that the consideration of microbiodiversity in economic valuation will help to find essential assets and guide decision-makers to conserve and protect the economic value of highly diverse microbial communities for future generations.

Description: Highlights • Role of salt leaching in seafloor stability is assessed via experiments and models. • Undrained cohesive strength of clayey silt subjected to leaching decreased by 50%. • Failure occurs when flushed layer is 〉3.5 m thick and slope gradient is 〉3°. Abstract Offshore freshened groundwater (OFG) has been documented in many continental margins worldwide. OFG systems are dynamic, expanding and contracting with falling and rise sea-levels. OFG has long been thought to be an important geomorphic agent in continental margins, either via active discharge at the seafloor, which can erode depressions, or the generation of excess pore pressure, which can deform sediments and cause slope failure. It has also been proposed that OFG flow can drive the loss of sediment shear strength via salt leaching, when seawater in pores is replaced by freshwater. Here, we measure changes in the geotechnical properties of seafloor clayey silt due to salt leaching using flushing experiments, and assess the implications of these changes on the stability of siliciclastic continental margins with 2D limit equilibrium modelling. We document a ~ 50% decrease in undrained cohesive strength of seafloor sediment after flushing, as well as a decrease in its shear strength, bulk density, and moisture content, which is similar to that reported for subaerial quick clays undergoing salt leaching. When applied to a theoretical submarine domain 300 m wide by 100 m high, we estimate that salt leaching can trigger slope failure when the thickness of the flushed layer is 〉3.5 m or when the slope gradient is 〉3°. Such conditions are primarily satisfied on the continental slope or the shallow seafloor close to the shoreline. Salt leaching by OFG flow merits consideration as a potential mechanism destablising submarine sedimentary slopes.

Description: Knowledge of temporal patterns of past explosive eruptions is necessary to understand possible future eruptive behavior. However, volcanic records based on geological reconstructions remain incomplete. This inference is true not only for remote and sparsely populated areas like the Aleutian or Kurile-Kamchatka arcs, but also for Europe, where past large explosive events are continuously recognized in the geological record. Here we report the first age and geochemical data on the violent middle to late Pleistocene explosive eruptions from the Elbrus volcanic center (Greater Caucasus), which towers over the densely populated regions in southern Russia and Georgia. We attribute six disparate ash deposits found in the terrestrial and marine sediments along the SE European margin to the Elbrus volcanic center based on major and trace element compositions of individual shards of volcanic glass and radiogenic Sr-Nd-Pb isotope compositions of bulk tephra. We suggest that these deposits represent products of five different eruptions that were dispersed over distances of more than 150–560 km from their source. Three of four eruptions are dated at 522 ± 36, 258 ± 13, and 84.6 ± 7.4 ka by a combined zircon U–Th–Pb and (U–Th)/He approach. One sample revealed an overdispersed spectrum of single crystal (U–Th)/He dates with an average of 176 ± 40 ka. Zircon characteristics and statistical deconvolution of the geochronology data suggest that this sample contains zircon crystals from two different eruptions tentatively dated at 156.5 ± 7.7 ka and 222.8 ± 13 ka. These eruption ages represent the first recognition of a suite of large pumiceous eruptions from the Elbrus volcanic center postdating the previously known explosive activity, documented by ∼800 ka old welded tuffs. These data also provide the first geochemical and geochronological characterization of both proximal and distal Elbrus tephra glasses and contribute to the global tephra database, permitting the identification of Elbrus tephras in distal terrestrial and marine paleoenvironmental archives and hence their use as paleoclimate and archaeological markers. We consider the significance of the identified tephras for paleoenvironmental research and show their potential for tephrochronological studies in the East European Plain and adjacent areas.

Description: Highlights: • First abundance of MPs in offshore sediments along South-Eastern Mediterranean • Mean MPs ranged between 1126 ± 1363 MPs/kg. • Most abundant shapes were fibers and films. • Most abundant polymer types were PP and PE. • Coastal landfills and wastewater discharges shaped spatial distribution of MPs. Few studies on microplastics (MPs) in the marine environment have been conducted along the Eastern part of the Mediterranean Sea and even fewer along the Lebanese coast. This study aims to determine MPs contamination for the first-time in coastal and continental shelf sediments collected along the Lebanese shores, South-Eastern Mediterranean Sea. Sediments were collected as transects in 10 sites with a total of 23 samples between 2 and 120 m depth and suspected MPs were assessed by moving farther from land-based sources. Microplastics concentrations ranged between 0 and 4500 MPs/kg of dry sediment (1126 ± 1363 MPs/kg). Polypropylene, polyethylene, polyethylene terephthalate and polystyrene were the polymers identified on micro-Raman. Coastal landfills and raw sewage effluents were identified as the main sources and routes for MPs into the Lebanese coastal marine environment. This study serves as the first database reporting MPs in continental shelf sediments in the South-Eastern Mediterranean

Description: Highlights: • The fate of PS microbeads in an exposure experiment was assessed over 50 h. • Targeted and realized MP concentrations can differ largely in controlled laboratory experiments. • Clearance rates of mussels were significantly decreased in the presence of MP. • Reduction of clearance rates was more pronounced in mussels that had recently spawned. Abstract: The fate of microplastic particles (MP) in exposure experiments is mostly unclear. We measured the recovery of polystyrene (PS) microbeads, which were applied in various concentrations from 0.07 to 47.47 beads/ml, from the different compartments of an experimental system with mussels (Mytilus spp.). At the end of the experiment, we detected a significant loss of MP indicating that the mussels were exposed to less particles than intended. If such a discrepancy remains un-recognized by the experimenter, observed effects are related to an inaccurate particle concentration. Additionally, we observed reduced clearance rates of the mussels in the presence of MP and the effect size increased with increasing particle concentration. This effect was more pronounced in mussels that had recently spawned than in mussels that still had mature gonads. This is a hint that effects of MP may depend on the reproductive status of an organism.

Description: Highlights • Zinc and copper isotope characterization of metalliferous sediments formed by brine pool deposition in the Atlantis II Deep. • Enrichments of light zinc and copper isotopes in sediments when compared to the hydrothermal inputs to the basin. • Isotopic data are consistent with metal sulfide precipitation and lesser adsorption of metals onto Si-Fe-OOH particles. • Increase of δ66Zn with increasing distance from hydrothermal metal release due to uptake of light isotopes by metal sulfides. • Zinc isotope patterns due to metal sulfide precipitation could be of interest in mineral exploration. Abstract This study provides a zinc and copper stable isotope characterization (δ66Zn, δ68Zn, and δ65Cu) of metalliferous seafloor sediments from the Atlantis II Deep, a hydrothermally influenced brine basin in the Red Sea. Samples collected from box cores that capture the entire stratigraphy in the Deep have δ66Zn and δ65Cu values of −0.31 to 0.34 ‰ (0.02 ‰ median) and − 1.81 to 1.02 ‰ (−0.34 ‰ median) relative to the JMC-Lyon and NIST SRM 976 standards, respectively. These results suggest enrichments of light stable isotopes in sediments compared to the hydrothermal inputs to the basin, which likely overlap the mantle-like isotopic signatures of basalts beneath the Deep. Such shifts to lower δ66Zn and δ65Cu values are consistent with widespread metal sulfide deposition from the brines because sulfide anions preferentially consume the light stable isotopes of zinc and copper. However, this interpretation contrasts with observations in the open ocean, where the fractionation of zinc and copper stable isotopes is strongly influenced by biological utilization and organic matter. Previous studies proposed that metal deposition in the Atlantis II Deep is also driven by adsorption onto iron oxides/hydroxides and their weakly crystalline (Si-)Fe-OOH precursor phases within the brines. However, because this process should accumulate heavy zinc and copper stable isotopes, its influence on isotopic fractionation is likely limited. Controls by metal sulfide precipitation are also indicated by spatial covariations between δ66Zn and concentrations of zinc and copper, that is, δ66Zn values increase whereas metal contents decrease with distance away from hydrothermal venting. Comparable trends are lacking for copper isotopes, perhaps because of additional influence by redox processes or, compared to zinc, a much stronger influence by adsorption onto (Si-)Fe-OOH phases, particularly in areas distal to hydrothermal venting where reduced sulfur could be scarce. Collectively, our results from the Atlantis II Deep indicate that zinc and copper stable isotopes could provide information about base and precious metals deposits from similar paleoenvironments. Firstly, zinc and copper stable isotopes shed light on metal sourcing and accumulation processes. Secondly, mineral precipitation in hydrothermally influenced brine pools produces zinc stable isotope patterns that, at least theoretically, could be of interest in mineral exploration at sub-basin and deposit scales.

Description: The subduction of seamounts and basement ridges affects the structure, morphology, and physical state of a convergent margin. To evaluate their impact on the seismo-tectonic setting of the subduction zone and the tectonic development of the lower subducting and upper overriding plate, it is essential to know the precise location of subducted topographic features under the marine forearc. Offshore Northern Chile, the Iquique Ridge represents a broad zone of complex and heterogeneous structure of variable width on the oceanic Nazca Plate, which complicates attempts to project it beneath the forearc of the Chilean subduction zone. Here we use a state-of-the-art seismic reflection data processing approach to map structures related to ridge subduction under the marine forearc with unprecedented accuracy and resolution and evaluate their impact on the deformation of both the plate boundary and the upper plate. We show that significant ridge-related topography is currently subducting south of 20.5 °S and that the combined effect of horst and graben subduction with subduction of Iquique ridge-related thickened and elevated crust causes an upward bulging of the entire upper plate from the plate interface up to the seafloor as well as the presence of kilometer-scale anticlinal structures observed in multibeam bathymetric data that are approximately aligned with horsts seaward of the trench. In the area affected by the subducting ridge, a frontal prism is absent, which may relate to frontal subduction erosion caused by the excess lower plate topography. In contrast farther towards the north, where only isolated seamounts subduct, a small frontal prism and a slope/apron sediment cover down to 3000 m water depth are found.

Description: Highlights • Probeebei mirabilis with or without anemone as indicator of changed environment. • 26 years after disturbance population densities changed significantly. • Possible delayed response to anthropogenic disturbance experiment. • Need for long-term (〉30 yrs) monitoring surveys post-disturbance in the abyss. The deep Peru Basin is characterised by a unique abyssal scavenging community featuring large numbers of hermit crabs (Probeebei mirabilis, Decapoda, Crustacea). These are atypical hermit crabs, not carrying a shell, but on some occasions carrying an anemone (Actiniaria). The reason why some hermit crabs carry or not carry anemones is thought to be indicative of a changed environment, outweighing the cost/benefit of their relationship. Here we present the temporal variation of abundances of P. mirabilis with and without anemones, spanning more than two decades, following a benthic impact experiment. An overall decrease in hermit crab densities was observed, most noticeable and significant after 26 years and characterised by a loss of Actiniaria on the Probeebei mirabilis' pleon. Whether this is a delayed response to the benthic impact experiment carried out 26 years’ prior or a natural variation in the population remains to be corroborated by an extension of the time-series. Attention is drawn to the limitations of our knowledge over time and space of the abyssal community dynamics and the urgent necessity to fill in these gaps prior to any type of deep-sea exploitation.

Description: Most continental arcs are built up over a long time (≥100 myr), and while subduction may be ongoing throughout this interval, magmatism appears to be highly episodic. This episodic behaviour is characterized by high-flux magmatic events but an overall low rate of magmatism. The causes of high-flux magmatic events (“flare-ups”) are enigmatic in many continental arcs. Bulk-rock Sr, Nd, and Pb isotopes, as well as zircon O and Hf isotopes, imply that the mantle and the continental crust can be involved in magmatic flare-ups. However, the relative contributions of mantle vs. crust with changes in eruption rates can differ from arc to arc. The Cenozoic magmatic arcs of Iran, built on mature continental crust, are an excellent candidate for studying the geochemical-isotopic feedback of magmatic pulses to understand the triggers for a flare-up. Our new data constrain the timing of the flare-up in NE Iran to the Early to Middle Eocene (51–43 Ma). This flare-up is characterized by the outpouring of high-K calc-alkalic to shoshonitic magmas at ∼110 ± 8 km3/myr - km. Geochemical modelling using the “Arc Basalt Simulator version 3″ shows that the high-K trachybasalts, moderately to extremely depleted in high-field strength elements, can be derived from the shallower (3.0 GPa; 870 °C) to deeper parts (5.0–5.4 GPa; 965–980 °C) of a subducting slab with ∼1.0 to 5.5 % slab melt flux. Mixing modelling using Sr, Nd, and Pb isotope data indicates that the Torud mafic-intermediate magmatic rocks can be generated by adding ∼ 1% to 〈6% of slab components (50% AOC: 50% sediment) to an Indian MORB-like mantle. Our results suggest that the high magmatic fluxes in NE Iran were instigated mainly by Eocene slab steepening after Paleocene flat-slab subduction, resulting in enhanced upwelling and melting of a volatile-enriched asthenospheric mantle.

Description: A genetic link between the Georgia-Islas Orcadas and Meteor guyots on opposite sides of the South Atlantic was proposed based on seafloor morphology and tectonic reconstructions. Here we test this model with geochemistry. We present new major and trace element and Sr, Nd, Pb, Hf radiogenic isotope data from volcanic and sedimentary rocks from Meteor Rise (ODP Site 703) and Georgia-Islas Orcadas Rise (ODP Sites 698, 699, and 701). Site 698, 699 and 703 volcanic rocks have largely overlapping initial Sr-Nd-Pb-Hf isotope ratios ((87Sr/86Sr)i = 0.70278–0.70660; (143Nd/144Nd)i = 0.51217–0.51283; (206Pb/204Pb)i = 18.09–18.75; (176Hf/177Hf)i = 0.28246–0.28299), extending from the Shona Hotspot track field (consisting of Richardson guyot, Agulhas Ridge and Meteor guyot samples) towards Proterozoic continental crust. Site 701 samples have slightly depleted isotopic compositions similar to southern Mid-Atlantic Ridge (SMAR) basalts, representing the upper mantle. These data support derivation from a common mantle plume, having formed contemporaneously as a single continuous hotspot track, which was subsequently divided by a ridge jump. Modelling of the isotope data show that binary mixing between an average Shona anomaly composition and an upper continental crustal component with a composition similar to the Site 698 sandstones can explain the data by 10–30% upper crustal assimilation to generate the composition of the Site 698, 699 and 703 volcanic rocks. Therefore, our geochemical data confirm the dismemberment of the Shona Hotspot track by a ridge jump and its subsequent seafloor spreading.

Description: Seaweed (macroalgae) has attracted attention globally given its potential for climate change mitigation. A topical and contentious question is: Can seaweeds' contribution to climate change mitigation be enhanced at globally meaningful scales? Here, we provide an overview of the pressing research needs surrounding the potential role of seaweed in climate change mitigation and current scientific consensus via eight key research challenges. There are four categories where seaweed has been suggested to be used for climate change mitigation: 1) protecting and restoring wild seaweed forests with potential climate change mitigation co-benefits; 2) expanding sustainable nearshore seaweed aquaculture with potential climate change mitigation co-benefits; 3) offsetting industrial CO2 emissions using seaweed products for emission abatement; and 4) sinking seaweed into the deep sea to sequester CO2. Uncertainties remain about quantification of the net impact of carbon export from seaweed restoration and seaweed farming sites on atmospheric CO2. Evidence suggests that nearshore seaweed farming contributes to carbon storage in sediments below farm sites, but how scalable is this process? Products from seaweed aquaculture, such as the livestock methane-reducing seaweed Asparagopsis or low carbon food resources show promise for climate change mitigation, yet the carbon footprint and emission abatement potential remains unquantified for most seaweed products. Similarly, purposely cultivating then sinking seaweed biomass in the open ocean raises ecological concerns and the climate change mitigation potential of this concept is poorly constrained. Improving the tracing of seaweed carbon export to ocean sinks is a critical step in seaweed carbon accounting. Despite carbon accounting uncertainties, seaweed provides many other ecosystem services that justify conservation and restoration and the uptake of seaweed aquaculture will contribute to the United Nations Sustainable Development Goals. However, we caution that verified seaweed carbon accounting and associated sustainability thresholds are needed before large-scale investment into climate change mitigation from seaweed projects.

Description: Highlights: • The cold-water coral Desmophyllum pertusum from reefs off Angola showed the same respiration rates at hypoxic and normoxic oxygen concentration. • The respiration rates measured are in the same order of magnitude as those previously observed for the species under normoxic conditions in other areas. Abstract: Large, well-developed and flourishing reefs dominated by the cold-water coral Desmophyllum pertusum have recently been discovered along the Angola margin in the southeastern Atlantic Ocean living under very low oxygen concentrations (0.6–1.5 mL L−1). This study assessed the respiration rates of this coral in a short-term (10 days) aquarium experiment under naturally low oxygen concentrations (1.4 ± 0.5 mL L−1) as well as under saturated oxygen concentrations (6.1 ± 0.6 mL L−1). We found no significant difference in respiration rates between the two oxygen concentrations. Furthermore, the respiration rates of D. pertusum were in the same order of magnitude as those of the same species living under normoxic conditions in other areas. This work expands the current knowledge on the metabolic activity of cold-water corals under hypoxic conditions, evidencing that low oxygen conditions are not a general limiting factor for the overall distribution of D. pertusum.

Description: Highlights • Detailed analysis of temperature, salinity and oxygen variations in the Baltic Sea for the period 1950 to 2020. • Linear trend of SST of 0.4°C per decade. • Trend in SST follows closely the air temperature variation. • Accumulated river runoff explains 70% of the variability of the mean salinity. • Decreasing oxygen concentrations are anti-correlated with temperature development. Variations of temperature, salinity and oxygen of the Baltic Sea on interannual to decadal timescales were studied for the period from 1950 to 2020. Both observational data and the output of a numerical circulation model of the Baltic Sea were analyzed. In addition, we investigated the influence of atmospheric parameters and river runoff on the observed hydrographic variations. Variability of sea surface temperature (SST) closely follows that of air temperature in the Baltic on all timescales examined. Interannual variations of SST are significantly correlated with the North Atlantic Oscillation in most parts of the sea in winter. The entire water column of the Baltic Sea has warmed over the period 1950 to 2020. The trend is strongest in the surface layer, which has warmed by 0.3–0.4°C decade−1, noticeably stronger since the mid-1980s. In the remaining water column, characterized by permanent salinity stratification in the Baltic Sea, warming trends are slightly weaker. A decadal variability is striking in surface salinity, which is highly correlated with river runoff into the Baltic Sea. Long-term trends over the period 1950–2020 show a noticeable freshening of the upper layer in the whole Baltic Sea and a significant salinity increase below the halocline in some regions. A decadal variability was also identified in the deep layer of the Baltic Sea. This can be associated with variations in saltwater import from the North Sea, which in turn are influenced by river runoff: fewer strong saltwater inflows were observed in periods of enhanced river runoff. Furthermore, our results suggest that changes in wind speed have an impact on water exchange with the North Sea. Interannual variations of surface oxygen are strongly anti-correlated with those of SST. Likewise, the positive SST trends are accompanied by a decrease in surface oxygen. In greater depths of the Baltic Sea, oxygen decrease is stronger, which is partly related to the observed increase of the vertical salinity gradient.

Description: Nutrients and nutrient-like dissolved trace metals (dTMs) are essential for the functioning of marine organisms and therefore form an important part of ocean biogeochemical cycles. Here, we report on the seasonal distributions of dissolved zinc (dZn), nickel (dNi), copper (dCu), cadmium (dCd), aluminum (dAl), and nutrients on the Northeast Atlantic continental margin (Celtic Sea), which is representative for temperate shelf seas globally. Variations in surface water dTM and nutrient concentrations were mainly regulated by seasonal changes in biological processes. The stoichiometry of dTMs (especially for dCu and dZn) and nutrients on the continental shelf was additionally affected by fluvial inputs. Nutrients and dTMs at depth on the continental slope were determined by water mass mixing driven by ocean circulation, without an important role for local remineralization processes. The Mediterranean Outflow Waters are especially important for delivering Mediterranean-sourced dTMs to the Northeast Atlantic Ocean and drive dTM:nutrient kinks at a depth of ~1000 m. These results highlight the importance of riverine inputs, seasonality of primary production and ocean circulation on the distributions of nutrients and nutrient-like dTMs in temperate continental margin seas. Future climate related changes in the forcing factors may impact the availability of nutrients and dTMs to marine organisms in highly productive continental shelf regions and consequently the regional carbon cycle.

Description: This study investigates the seasonal variability of the cloud radiative effects (CREs) over Congo Basin (CB) using 15-year observations from Clouds and the Earth's Radiant Energy System (CERES) Energy Budget and Filled (EBAF) Ed4.1 level 3b dataset involving CERES and Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on board Terra and Aqua satellites. The relationships between CREs and cloud properties such as total cloud fraction (TCF), cloud top height (CTH), cloud top temperature (CTT) and cloud optical thickness (COT) are checked. An evaluation of Coupled Model Intercomparison Project (CMIP) Phase 6 in capturing the seasonal cycle of CREs as well as the magnitudes of the CREs along the seasonal cycle is also performed. This study shows a net cloud cooling effect of −8.4 W/m2 and − 43.9 W/m2 respectively at the top of the atmosphere (TOA) and at the surface, leading to a net warming effect of 35.67 W/m2 in the atmosphere. This value implies a large energy source over the Central Africa (CA) atmospheric column. The associated relationships between CREs and cloud properties show that the shortwave CRE is more sensitive to TCF and optical thickness whereas its longwave counterparts is more sensitive to CTH, CTT and COT at the TOA and in the atmosphere. All of the four CMIP6 models used in this study can capture the spatial pattern of CREs as well as their seasonal cycle but misrepresent intensity of CREs. Results also show that a better-simulated TCF considerably reduces the intensity of the annual mean underestimation in both longwave and shortwave CRE for some CMIP6 models, but not for models with overestimated shortwave CRE.

Description: The sources, distribution, and fate of particulate organic matter (POM) in estuaries are dynamic and complex, influenced by highly intensive human activities and high productivity. In this study, water samples were collected along the Changjiang Estuary salinity gradient and adjacent sea (CEAS) in February and May 2017. Particulate organic carbon (POC), particulate nitrogen (PN), the δ13C isotope values and major biochemical constituent (total particulate amino acids, TPAA) were measured. The concentrations of POC, PN, and TPAA showed an overall decreasing trend from the river end-member to the open sea; however, their maximum always occurred around the turbidity maximum zone (TMZ). Concentrations of POC and TPAA showed a negative correlation with salinity and a positive correlation with chlorophyll a, indicating that the variation in POM concentrations and composition was mainly controlled by both terrigenous input and in situ phytoplankton production. The δ13C values gradually increased from the river mouth to the open sea in both winter and spring, in contrast to the molar C/N, reflecting the transition from terrestrial POC to phytoplankton-derived fresh POC with increasing salinity. Major biochemical indicators of TPAA/POC (%) and the degradation index (DI), showed a gradual shift towards more bioactive POM with increasing salinity in spring, although low TPAA/POC (%) values appeared within the TMZ. In spring, POC reactivity was higher than in winter. The proportions of glycine (Gly) and serine (Ser) were higher in winter, indicating that POM had suffered extensive degradation. Based on a two end-member mixing model, the contribution of marine POC in spring (53 ± 14%) was significantly greater than in winter (39 ± 19%), indicating that phytoplankton-derived POM was dominant in spring, associated with the increase in phytoplankton biomass from winter to spring. Based on mass balance, a box model showed evidence of a net POC sink over the Changjiang estuary and its adjacent East China Sea shelf in both winter and spring, with a net POC budget of 20.49 ± 7.01 and 15.87 ± 6.57 kmol s−1, respectively. Results illustrate that the spatio-temporal distribution of POM varies distinctively and will further affect the variability in its composition and reactivity in the CEAS.

Description: We present textural and chemical analyses of minerals from a 150 m thick sequence of submarine mid-ocean ridge basalts from the South China Sea in order to showcase the effect of variations in magma cooling rates on mineral texture and mineral composition. Groundmass plagioclase and clinopyroxene show gradual changes in texture and composition as flows grade from slowly cooled, meter-thick massive flows to more rapidly cooled dm-thick pillow lobes with quenched glassy margins. The corresponding change in cooling-rate is estimated to vary from 〈1 to ≥100 °C/h. With increasing cooling rate, plagioclase forms elongated, sector-zoned swallow-tail crystals. Sector zoning is associated with increasing FeO (up to 1.5 wt%) and MgO (up to 0.6 wt%) abundances at near-constant anorthite (An), related to a two orders of magnitude increase in growth rate. Sr, Ba, Li and Ti abundances remain constant and appear unaffected by kinetic factors at such growth rates. With increasing cooling rate clinopyroxene becomes dendritic, and its composition is sensitive to changes in crystallization conditions. Increasing cooling rate (〈1 to ≥100 °C/h) leads to increasing Al2O3 (average of 3.2 to 4.3 wt%), TiO2 (1.3 to 2.8 wt%) and Na2O (0.37 to 0.44 wt%) and a decrease in SiO2 (50.1 to 46.4 wt%) and Mg#Fetot, i.e., molar MgO/(MgO + FeOtot), from 71.3 to 53.1. Trace element abundances (Y, Zr, Ce, V, Sr) in clinopyroxene increase by up to an order of magnitude at cooling rates ≥100 °C/h and become more heterogeneous spatially. These results support experimental evidence that rapid crystal growth leads to significant departure of mineral compositions from equilibrium, in particular for clinopyroxene. Although plagioclase composition remains relatively insensitive to changes in growth conditions at the studied cooling rates, the sensitivity of clinopyroxene composition to growth rates imply that it should be used with caution as a tool to infer magmatic crystallization conditions.

Description: Highlights: • The dust storm led to new record-low visibility observations in Chinese cities. • Taklamakan dust emissions linked to Mongolian cyclone via NLLJs for the first time. • Gobi dust affected most cities, while Taklamakan dust influenced the West of China. Abstract: In mid-March 2021, one of the strongest dust storms of the last decade hit East Asia with adverse impacts on socio-economic activities and loss of life. The aim of this study is to assess the atmospheric dynamics involved in the temporal evolution of the Mongolian extra-tropical cyclone driving the dust event in different dust source regions in East Asia and to quantify to what extent the event was unusual for the first time. To that end, we use observation and model data from different sources. We identify that dust aerosols of the event primarily originated in the Gobi Desert. The anomalously strong dust-emitting winds were here associated with the passage of a cold front and exceeded the 99th percentile of the near-surface wind climatology for March 1992–2021 by far. Over the Loess Plateau, the dust deposition mostly exceeded the regional dust emission, indicative of the region being a net sink for dust aerosols, even during a high-impact event like in mid-March 2021. The formed dust aerosol layer of thousands of kilometers in extent led to sharp decreases in the air quality across China with record-high urban particulate matter concentrations, poor air quality, and low atmospheric visibility. Our results highlight that also the Taklamakan Desert contributed to the dust outbreak in the Western part of China. The dust emissions in the Taklamakan Desert were associated with nocturnal low-level jets that were favored by the cold air intrusion. It provides the first evidence for a link between different dust-emission mechanisms across East Asian Deserts during synoptic-scale dust outbreaks.

Description: Calcium (Ca) isotopes (δ44/42Ca) in serum and urine have been suggested as novel sensitive markers of bone calcification. The response of δ44/42Ca to acute changes in Ca homeostasis, has not yet been demonstrated. We measured serum Ca and δ44/42Ca in rats maintained on a standard and a 50% Ca reduced diet for 4 weeks, and after injection of 1 mg/kg of the calcimimetic AMG-416, 24 h prior to sacrifice. AMG-416 decreased serum Ca by a maximum of 0.38 ± 0.10 and 0.53 ± 0.35 mmol/l after 12 and 6 h, respectively, in the standard and low-Ca diet groups (p = 0.0006/0.02), while serum δ44/42Ca did not change over 24 h in both groups. Urinary Ca concentrations were higher 24 h after AMG-416 injection in both groups (p = 0.03/0.06), urine δ44/42Ca was not different compared to the untreated control groups. Our data does not show acute changes in δ44/42Ca in response to a single dose of AMG-416 within 24 h after injection, possibly due to a lack of bone calcification.

Description: Stable barium (Ba) isotopes are emerging as tracers for the recycling of crustal material into the mantle. Small but significant Ba isotope variations have been found in global MORB (δ138/134Ba values of −0.04‰ to 0.15‰), but the processes causing these Ba isotope variations remain poorly understood. In addition, uncertainties still exist in the estimate of the Ba isotope composition of the depleted upper mantle. Here, we present a systematic study of Ba isotopes for well-characterized MORB glass samples from the South Mid-Atlantic Ridge (SMAR) between 5 and 11°S, which span a wide range of radiogenic isotope ratios and trace element contents. Our results show that the northernmost segment A0 basalts with highly depleted radiogenic isotope compositions have δ138/134Ba values ranging from −0.02 to 0.05‰. In comparison, the δ138/134Ba values of the isotopically enriched basalts from the A1-A4 segments vary from 0.02 to 0.11‰. Thus, while small, the enriched components involved can be observed to modify the Ba isotope composition of the mantle source beneath A1-A4 segments. Combining our new measurements with literature data, this study places new constraints on the Ba isotope composition of the depleted upper mantle, as well as the origin of Ba isotope heterogeneity in MORB. The Ba isotope composition of the depleted upper mantle in the absence of recycled components is estimated to have a δ138/134Ba value of 0.03 to 0.05‰, which can be adopted as the baseline for using Ba isotope ratios as a tracer of mass transfer processes between the crust and mantle. In comparison, global MORB have δ138/134Ba values ranging from −0.04‰ to 0.15‰. No global correlation is observed between Ba isotope ratios and geochemical parameters that record mantle enrichment, indicating that the Ba isotope variations in MORB cannot be simply ascribed to the addition of some single component, such as sediment. Models for melting and mixing between recycled materials and depleted mantle suggest that the variable Ba isotope compositions of the enriched MORB require a contribution from recycled altered oceanic crust and crustal sedimentary materials. Therefore, these recycled components both play important roles in the chemical budget of the convecting upper mantle, especially for incompatible elements such as Ba.

Description: Sedimentary molybdenum (Mo) and uranium (U) enrichments have been widely used as a proxy for redox conditions in oxygen-depleted marine paleo-environments. However, in a dynamic upwelling system the seasonal fluctuations from oxic to completely anoxic-sulfidic bottom waters and lateral sediment transport can modify the primary Mo and U signal of the sediment, which in turn may impact paleo-redox interpretations. In this study we present pore water and solid phase data collected at two cross shelf transects during the ‘more oxygenated’ austral winter and ‘anoxic’ austral summer to study the influence of spatially and seasonally contrasting redox conditions on the formation of authigenic Mo and U enrichments in organic carbon (TOC) rich mud belt sediments on the Namibian shelf. A mass balance was established for each element based on diffusive fluxes and element mass accumulation rates to evaluate the respective mechanisms of trace metal delivery, accumulation and recycling. Mo is delivered to the sediment in its dissolved form via diffusion across the sediment–water interface, especially during austral summer when bottom waters are anoxic and surface sediments are highly sulfidic. In the center of the inner shelf mud belt, the benthic Mo fluxes of up to 37 nmol cm−2 yr−1 into sulfidic surface sediments are the highest ever reported for reducing sulfidic systems and agree with the rate of Mo accumulation in the solid phase. Concurrently, high sedimentation rates and low terrigenous input limit solid phase Mo accumulation on the Namibian shelf. In ancient marine sediments, this mode of Mo cycling can be identified by low Mo/TOC ratios of ∼2 similar to those found in sediments deposited below the perennial oxygen minimum zone on the Peruvian shelf and to those found in deposits of the Cretaceous Oceanic Anoxic Event 2. Diffusive U fluxes into the sediment are generally too low to account for the sedimentary enrichment leading to the conclusion that U is delivered mainly in particulate form. In areas with anoxic bottom water, shallow dissolved U maxima directly below the sediment water interface and rather low sedimentary U content indicate that particulate U is recycled and largely released back into the bottom water. At sites where bottom water oxygen concentrations vary from anoxic to completely oxic on seasonal timescales, the depth at which Mo and U are removed from pore waters moves vertically within the sediment column thus defining a layer between the sediment surface and ∼20 cm depth, in which Mo and U accumulate in the solid phase. Our results emphasize the importance of short-term redox fluctuations in the bottom waters and underlying sediments, as well as lateral sediment transport for the authigenic enrichment of redox-sensitive trace metals in reducing shelf sediments. The relative enrichment patterns identified might be useful for the reconstruction of open marine anoxia in the geological past.

Description: Extensive and protracted volcanism in the Carpathian-Pannonian Region climaxed during the Early to Middle Miocene with series of major ignimbrite-forming eruptions with their products dispersed across the Alpine-Mediterranean Region. The spatial and temporal dispersion of these volcanic horizons make them potentially important stratigraphic markers throughout the region, allowing better understanding of temporal and spatial changes in depositional environments and paleoclimate. Several of these Middle Miocene volcaniclastic layers are preserved in stratigraphically and environmentally variable sedimentary facies on Mt. Medvednica, located in the North Croatian Basin. In order to decipher the age, depositional environment and provenance of two volcaniclastic horizons intercalated within Central Paratethys marine sediments on Mt. Medvednica, we applied an integrated approach of volcanological, geochronological, and paleontological analyses. New high-precision zircon geochronology and volcanic glass geochemistry data allow to distinguish two primary rhyolitic volcaniclastic horizons derived from distinct eruptions, “Plaz“, and the “Bidrovec“, dated at 14.937 ± 0.012 Ma and 14.835 ± 0.012 Ma. Distinguished mineralogical and geochemical data enabled the correlation of the older (“Plaz”) horizon on Mt. Medvednica with the Demjén eruption, one of the six major Early–Middle Miocene ignimbrite-forming eruptions of the Carpathian-Pannonian Region. However, a correlation of the younger (“Bidrovec“) horizon and assignment to a specific eruption could not be established due to a lack of compositional data from coeval eruption products throughout the region. The newly gathered data establishes both “Plaz” and “Bidrovec” pyroclastic deposits as valuable marker horizons for regional reconstructions, and enable a better understanding of the eruption chronology and tephrostratigraphy of the Carpathian-Pannonian Region.

Description: For the first time we used lab and wind-wave tank experiments to prove the concept of using Mg(OH)2 for the ocean alkalinity enhancement and carbon dioxide removal approach (OAE-CDR). Experiment results showed up to 370 μmol kg−1 seawater total alkalinity (TA) increase without precipitation, stable enhanced TA, and OAE-CDR efficiency (ΔDIC/ΔTA) consistent with theoretical calculation. Based on the experimental results, we calculated the global Mg(OH)2 OAE-CDR efficiency and CO2 sink from this approach. The efficiency is in favor of lower initial DIC to TA ratio, lower temperature, and higher atmospheric CO2, and therefore is the lowest at the equator (0.7–0.8) and increases with latitude (1.0–1.2 above 70 N/S). However, factoring in the ocean's surface area, low latitude regions can absorb more atmospheric CO2. We conservatively estimate that 44. 4 × 109 ton of CO2 (∼ 3.3 times of current annual CO2 sink in the ocean) could be removed from the atmosphere with 175 μmol kg−1 Mg(OH)2 (equivalent to 350 μmol kg−1 of TA) added to the top 10 m of the ocean.

Description: The presence of gas hydrates is well known in the marine realm southwest off Taiwan due to the widespread distribution of bottom simulating reflectors in seismic records. To learn more about gas hydrate systems and their dynamics at passive and active margins, we drilled boreholes with MARUM-MeBo200 seafloor drill rig at areas where geophysical indications for gas hydrates have been detected in the past. Several gas hydrate proxies like negative chloride anomalies in the pore water, cold spots detected by infrared thermal scans on cores, increased resistivity, and lithological parameters clearly showed the presence of hydrates in the drilled sections. However, gas hydrate was not recovered by MeBo most likely because of small crystal sizes which dissociated during recovery from the seafloor. Three holes were drilled at southern summit of Formosa Ridge down to 126 m below seafloor (mbsf) and recovered sediments from which in situ hydrate saturation values were estimated between 1 and 10% at 15–42 mbsf and even higher values of up to 38% below 100 mbsf. The latter are probably related to the sealing effect of carbonate precipitation which occur at 85–95 mbsf directly above the hydrate-enriched layer. Four holes were drilled at Four-Way Closure Ridge where a maximum drilling depth of 143.90 m was reached. Hydrate presence starts in 65 mbsf continuing down-core with a range of 1–29% gas hydrate saturation in fine-grained homogenous clay. An abrupt change to higher gas hydrate saturation values of up to 80% occurs below 109 mbsf where silty and sandy turbidite layers are often intercalated. Such high gas hydrate contents only occur in the sand layers and not in the fine-grained sediments intercalated to the sand deposits.

Description: Disposal of munitions at dumpsites in coastal seas was conducted after WW I and II. Also, large amounts of unexploded munitions from wartime activities litter the seafloor. Corrosion of munition shells causes release of toxic munition compounds (MCs). Furthermore, explosion risks increase due to large-scale economic developments in coastal waters. Seafloor munition clearance by commercial and military entities form an ongoing task to eliminate environmental and security risks. Munition detection primarily relies on geophysical techniques. However, these methods do not provide unequivocal signatures for ordnance and suffer from false positives. Here we assess chemical approaches using spectroscopic and spectrometric methods for ordnance detection in seawater with a primary focus on MCs, but also including chemical warfare agents. We discuss novel analytical techniques suitable for near real-time munition detection at sea, incorporating pre-concentration and matrix removal steps of seawater samples. We also describe emerging real-time technologies for on-site MC detection in coastal waters.

Description: Highlights: • Riverine DOC and POC dynamics reflect sub-basin land use and climate conditions. • Semi-distributed mass balance models show spatial and temporal changes. • An open source QGIS plug-in allows for scenario analysis of alternative land uses. • Future climate scenarios show major reductions of riverine DOC and POC export. Abstract: Dissolved organic carbon (DOC) and particulate organic carbon (POC) play a fundamental role in biogeochemical cycles of freshwater ecosystems. However, the lack of readily available distributed models for carbon export has limited the effective management of organic carbon fluxes from soils, through river networks and to receiving marine waters. We develop a spatially semi-distributed mass balance modeling approach to estimate organic carbon flux at a sub-basin and basin scales, using commonly available data, to allow stakeholders to explore the impacts of alternative river basin management scenarios and climate change on riverine DOC and POC dynamics. Data requirements, related to hydrological, land-use, soil and precipitation characteristics are easily retrievable from international and national databases, making it appropriate for data-scarce basins. The model is built as an open-source plugin for QGIS and can be easily integrated with other basin scale decision support models on nutrient and sediment export. We tested the model in Piave river basin, in northeast Italy. Results show that the model reproduces spatial and temporal changes in DOC and POC fluxes in relation to changes in precipitation, basin morphology and land use across different sub-basins. For example, the highest DOC export were associated with both urban and forest land use classes and during months of elevated precipitation. We used the model to evaluate alternative land use scenarios and the impact of climate on basin level carbon export to Mediterranean.

Description: Highlights • A fiber optic strain cable is used to monitor a fault offshore Catania, Sicily. • Brillouin laser reflectometry detects 2.5 cm of cable elongation on the seafloor. • The cable elongation may be caused by fault slip or by seabottom currents. • Submarine telecom cables are likely suitable to detect deformation on the seafloor. Abstract Oceans cover more than 70 percent of the Earth's surface making it difficult and costly to deploy modern seismological instruments here. The rapidly expanding global network of submarine telecom cables offers tremendous possibilities for seismological monitoring using laser light. Recent pioneer studies have demonstrated earthquake detection using lasers in onland and submarine fiber optic cables. However, permanent strain at the seafloor has never before been measured directly as it happens. With this aim, we deployed a dedicated 6-km-long fiber optic strain cable, offshore Catania Sicily, in 2000 m water depth, and connected it to a 29-km long electro-optical cable for science use. We report here that deformation of the cable equivalent to a total elongation of 2.5 cm was observed over a 21-month period (from Oct. 2020 to Jul. 2022). Brillouin laser reflectometry observations over the first 10 months indicate significant strain (+25 to +40 microstrain) at two locations where the cable crosses an active strike-slip fault on the seafloor, with most of the change occurring between 19 and 21 Nov. 2020. The cause of the strain could be fault slip or seabottom currents. During the following 11 months, the strain amplitude increased to +45 to +55 microstrain, affecting a longer portion of the cable up to 500 m to either side of the first fault crossing. A sandbag experiment performed on the distal portion of the cable (3.2–6.0 km) starting Sept. 2021 demonstrates how the fiber optic cable deforms in response to an applied load and how the deformation signal partially dissipates over time due to the elastic properties of the cable. These preliminary results are highly encouraging for the use of BOTDR (Brillouin Optical Time Domain Reflectometry) laser reflectometry as a technique to detect strain at the seafloor in near real time and to monitor the structural health of submarine cables.

Description: Growing demands for high-tech uses of rare earth elements (REE) result in their releases into the aquatic environment, but local anthropogenic sources and water chemistry reactions may vary in aquatic systems. In this study, we quantified the yttrium and REEs (REY) in the surface waters of the Pearl River Delta (PRD), Southern China, and investigated their sources and processes controlling the dissolved REY distributions from rivers towards the sea. Spatial variations of dissolved REY concentrations (〈0.4 μm) were observed in the surface water due to both natural and anthropogenic sources. Salt-induced flocculation removed colloidal REY from water during estuarine mixing, particularly at low salinity. In contrast, a significant increase of dissolved REY concentration with salinity suggested the occurrence of REY desorption from particles during estuarine mixing. The PAAS-normalized REE patterns (i.e., filtrates 〈0.4 μm and 〈3 kDa) showed a significant light REE (LREE) depletion relative to heavy REE (HREE) in dissolved fractions, indicating reactive LREE adsorption onto particles. Positive Gd anomalies in most waters revealed significant impacts from human activities, such as effluents from wastewater treatment plants in the PRD. In particular, the anthropogenic Gd contributed 90 % of the total dissolved Gd along the Pearl River and was conservatively mixed with saltwater in the estuary via the Humen outlet. Positive Sm anomalies were also observed in the PRD, indicating other point sources related to industrial activity. With the increase of urbanization and high demand for green technology, the REY anomalies could be a good indicator of human activities on assessing their fluxes and impacts on the aquatic systems.

Description: The Mahoney Seamount is a recently discovered volcanic edifice located 4 km north of the ultra-slow spreading Southwest Indian Ridge (SWIR). The SWIR is one of the slowest spreading ridges worldwide with a full spreading rate of ∼14 mm/year and low magmatic productivity. We report that highly vesicular basalts from the Mahoney Seamount have unradiogenic Nd-Hf together with radiogenic Sr isotopic compositions. Their distinct low 206Pb/204Pb isotope signature combined with high 207Pb/204Pb and 208Pb/204Pb is best explained by melting of a mantle that has been strongly influenced by stranded lower continental crust. The geographic distribution of the isotopic variability favors the idea of shallow recycling of lower continental crust isolated for a longer period contributing to melts forming Mahoney Seamount through off-axis fault systems. The isotopic composition of Mahoney Seamount lavas shares many characteristics with EM-1 sources and the DUPAL signature. Previous isotopic studies of the SWIR basalts proposed recycling of ancient subcontinental lithospheric mantle (SCLM) or pelagic sediments with oceanic crust to be responsible for this enriched isotopic signature. Lu/Hf and Sm/Nd ratios of pelagic sediments would result in decoupled 143Nd/144Nd and 176Hf/177Hf ratios. This decoupling is also observed in Ejeda-Bekily dikes from Madagascar, but those are believed to sample the SCLM dispersed in the Indian Ocean. However, Mahoney Seamount shows no decoupling in those isotopic systems and the restricted occurrence of the extreme lower continental crustal signature at Mahoney Seamount implies that the enriched isotopic signature has a different origin.

Description: In this study, we highlight the importance of permeability anisotropy on the hydrogeological regime of a ridge-flank hydrothermal system. Our study site, North Pond, is a marine sediment pond on ∼8 Ma seafloor in the North Atlantic, and represents a low-temperature, end-member ridge-flank hydrothermal system. Previous simulations of North Pond elucidated long-standing hypotheses concerning hydrothermal fluid and heat transport in the upper volcanic crust but failed to fully explain observed patterns of seafloor heat flux in this area. Here we use variography, a geostatistical method, to quantify relations between seafloor heat-flux measurements, and coupled numerical simulations of fluid and heat flow to simulate the hydrogeologic regime. Directional variography shows that heat-flux observations are correlated along-strike of the regional crustal fabric. Three-dimensional simulations that include permeability anisotropy are able to replicate seafloor heat-flux patterns across North Pond. The simulations that result in the best match to thermal data incorporate permeability anisotropy in the horizontal plane. We find that the feedback between permeability anisotropy and the asymmetric geometry of North Pond combine to promote advective removal of heat and mass within the crustal aquifer. These findings suggest that permeability anisotropy in the oceanic crust may influence ridge-flank hydrothermal circulation more broadly.

Description: Highlights • Submarine basaltic glasses from Pitcairn Island are uniformly high in δ98/95Mo. • Proterozoic pelagic sediments can explain radiogenic EM-1 and heavy Mo signatures. • Enriched “anoxic” signature found in both large low shear velocity provinces (LLSVPs). • Anoxic sediments buffer Precambrian subduction zone fluids to reducing conditions. • Subduction cycling of some redox sensitive metals to the mantle wedge was limited. Abstract Subduction redistributes elements between Earth's principal geochemical reservoirs, modifying the chemical composition of Earth's mantle, crust, atmosphere, and hydrosphere, and consequently having an impact on the evolution of life itself. Subduction of surface material that has been geochemically modified by low-temperature processes leads to mineralogical and chemical heterogeneities in mantle reservoirs over time and is recorded in modern ocean island basalts. One of the principal geochemical end members of the heterogeneous deep mantle, the enriched mantle 1 (EM-1) source of Pitcairn Island, has been attributed to the contribution of crustal material with vastly different chemical compositions and ages. The Mo isotope composition of lavas from Pitcairn Island constrains the nature of this recycled crustal component. Pitcairn lavas have elevated δ98/95Mo relative to the depleted mantle. The high δ98/95Mo is associated with high time-integrated 232Th/238U and 87Rb/86Sr, and low time-integrated 147Sm/144Nd and 238U/204Pb. These characteristics can be attributed to the recycling of nearly pristine pelagic sediments that were deposited in a Proterozoic anoxic deep-ocean into the sources of the Pitcairn Island lavas. The isotope composition of these lavas is similar to that of EM-1 hotspots from the South Atlantic, indicating the addition of reduced sediments in both of Earth's large low shear wave velocity provinces (LLSVPs). Consistent data from both locations imply that the subduction cycling of sedimentary redox-sensitive elements such as Mo, S, Se, and U into arc magmas was in these cases inefficient in the Precambrian and the chemical and isotopic signature of reduced sediments is preserved in the source of ocean island basalts bearing the EM-1 characteristics.

Description: he present study was undertaken to explore the effects of sulfamethazine (SMZ) dietary exposure on the enrichment of the intestine microbial structure, and antibiotic resistance gene (ARGs) transmission in marine medaka, with respect to antibiotic dose, duration, and sex. In male fish, a dietary exposure of 10 μg/L SMZ led to a heightened SMZ enrichment in the intestine, whereas metabolite (N-SMZ) levels were elevated at a higher exposure concentration (100 μg/L). Conversely, female fish exhibited stable levels of accumulation and metabolic rates across the exposure period. The composition of intestinal microorganisms revealed that exposure duration exerted a greater impact on the abundance and diversity of gut microbes, and microbial responses to SMZ varied across exposure time points. The expansion of Bacteroidetes and Ruegeria likely stimulated SMZ metabolism and contributed to the more balanced level of SMZ and N-SMZ observed in females. In males, short-term SMZ stress resulted in a disruption of intestinal homeostasis, while the rise in the abundance of the Fusobacteria and Propionigeniuma suggested a potential enhancement in intestinal anti-inflammatory capacity over time. Overall, female medaka exhibited greater adaptability to SMZ, and males appear to experience prolonged effects due to SMZ. A total of 11 ARGs and 5 mobile genetic elements (MGEs) were identified. Ruegeria is the main carrier of two types of MGEs (IS1247, ISSm2-Xanthob), and may serve as an indicator of ARG transmission. Therefore, it is rational to consider some fish breeding areas in natural waters as potential "reservoirs" of antibiotic resistance. This research will provide a valuable reference for the transmission of drug resistance along the food chain.

Description: Critical to the survival of island-based human societies is their resilience and adaptation to volcanic hazards. We here evaluate pre-Hispanic (before 15th century AD) land use patterns on the volcanic island of Tenerife, Canary Islands, Spain using obsidian hydration dating (OHD). The samples studied include archaeological artifacts and natural rock chips from multiple sites of different elevation and micro-climate settings. We systematically collected samples from the southern dry area around Barranco de las Monjas in the Bandas del Sur. These include a total of 28 isolated artifact scatters (here, a scatter is defined as a minimum spatial unit of artifacts distributed spatially limited range on the surveyed surface), one dwelling, and several pyroclastic deposits containing obsidian clasts. We also collected several artifacts adjacent to a large obsidian flow of Tabonal Negro in the Las Cañadas Caldera. Unsystematic surveys in north of Mt. Teide identified large obsidian outcrops located at Tabonal de los Guanches and Charco del Viento. Size differences among surface-derived obsidian artifacts (i.e., Bandas del Sur, Las Cañadas Caldera, Icod Valley) suggest that pre-Hispanic groups utilized obsidian from multiple outcrops over wide areas. Hydration analysis on 136 obsidian flakes collected from both surface and buried contexts showed only minor obsidian hydration rims (5% of total samples) and varied mean rim thicknesses (0.6–3.5μ). The low percentage of hydration rim formation may be caused by environmental factors such as wind erosion, thermal effects from volcanic or natural ground fires, or due to obsidian geochemistry (low SiO2 and water content of phonolitic obsidian). Surface-collected obsidian flakes from the southern dry area do contain hydration rims along internal fissure. The estimated hydration rates from these samples can provide an approximate age when compared to buried obsidian artifacts with associated radiocarbon dates.

Description: To examine the alteration of river-derived sediments through a large estuary and the implications for elemental cycling and global climate, this study analyses lithium (Li) isotopes and elemental concentrations (e.g., Li, Na, Mg, K, Ca, Fe and Al) of both the dissolved load and different phases of the sediment load (i.e., exchangeable, carbonate, oxide, clay and residue) in the Amazon estuary. The results show that river-derived sediments remove Li from the dissolved load, largely due to cation retention in secondary clays. By modelling the Li mass-balance and isotope fractionation, we estimate that the river-derived sediments gain 3–4 μg/g Li from the dissolved load in the Amazon estuary, with a Li isotope fractionation factor (αclay-solution) of approximately 0.975. Considering the whole Amazon estuary, the river-derived sediments remove around 3.6–4.8 × 109 g/yr of Li from the dissolved load. Specifically, around 1.0–1.7 × 108 g/yr of Li is removed from river water (∼1.8–3.0% of the dissolved Li discharge flux of the Amazon River) and around 3.5–4.7 × 109 g/yr of Li is removed from seawater, which represents a significant sink from the ocean. This estuarine Li sink is likely to be related to continental erosion rates; thus, continental weathering and erosion regimes could influence not only riverine Li input, but could also directly affect the Li sink, leading to a dual control on the Li budget and isotope composition in the ocean.

Description: Highlights • Comprida Volcanic System ∼3180 cal yr BP eruption was the latest at Flores Island. • Eruptive style shifted from Hawaiian-Strombolian to phreatomagmatic. • All five (maybe six) phreatomagmatic craters were formed during a single eruption. • CVS eruption is nearly contemporary with a large gravitational flank collapse. • Future hazard assessments should consider the hydrologic characteristics of Flores. Abstract The stratigraphy and eruptive history of a volcanic system are key to forecast the timing and style of future eruptions. Flores is a small volcanic island in the Azores Archipelago with no record of eruptions since its settlement in the 15th century, although at least six eruptions are known to have occurred during the Holocene. Thus, Flores must be considered potentially active, and its volcanic hazard should not be disregarded. The most recent eruptions clustered at two centres of activity: the Funda Volcanic System (FVS) and the Comprida Volcanic System (CVS). Here, we reconstruct for the first time the eruptive history of CVS, the youngest volcanic system of Flores. Based on detailed tephrostratigraphic and geomorphological work, combined with radiocarbon dating and glass shard geochemistry, we show that – despite featuring five (maybe six) phreatomagmatic craters – CVS was formed in a single volcanic eruption at ∼3180 cal yr BP. This eruption started with Hawaiian-style lava fountaining followed by Strombolian activity, dispersing tephra fallout across the central part of the island. Lava flows were also emitted during the initial phase, which drained to the west and cascaded over the older deposits of the massive slump of Fajãzinha–Fajã Grande, and possibly reached the coastline to form the Fajã Grande lava delta. The initial magmatic phase was followed by phreatomagmatic explosions that formed several maars and tuff rings. Hence, groundwater played an important role in the eruption by transforming a mild Hawaiian-Strombolian eruption into a highly explosive phreatomagmatic event, possibly due to oscillations in the eruption rate. The occurrence of a large landslide contemporary to the eruption, raises the possibility of a combined threat. A new and more robust volcanic hazard assessment for the island involving scientists and civil protection authorities is desirable.

Description: Submarine massive sulfide deposits on slow-spreading ridges are larger and longer-lived than deposits at fast-spreading ridges, likely due to more pronounced tectonic faulting creating stable preferential fluid pathways. The TAG hydrothermal mound at 26∘N on the Mid-Atlantic Ridge (MAR) is a typical example located on the hanging wall of a detachment fault. It has formed through distinct phases of high-temperature fluid discharge lasting 10s to 100s of years throughout at least the last 50,000 yrs and is one of the largest sulfide accumulations on the MAR. Yet, the mechanisms that control the episodic behavior, keep the fluid pathways intact, and sustain the observed high heat fluxes of possibly up to 1700 MW remain poorly understood. Previous concepts involved long-distance channelized high-temperature fluid upflow along the detachment but that circulation mode is thermodynamically unfavorable and incompatible with TAG's high discharge fluxes. Here, based on the joint interpretation of hydrothermal flow observations and 3-D flow modeling, we show that the TAG system can be explained by episodic magmatic intrusions into the footwall of a highly permeable detachment surface. These intrusions drive episodes of hydrothermal activity with vertical discharge and recharge along the detachment. The numerical simulations reveal that the high-temperature circulation system at TAG may be confined to a vertical zone of enhanced permeability that channelizes upflow and a recharge system that is hosted by the detachment surface with a high permeability of to . This revised flow regime reconciles problematic aspects of previously inferred circulation patterns and allows to identify the prerequisites for generating substantive seafloor mineral systems.

Description: Although parasitism is one of the most common species interactions in nature, the role of parasites in their hosts' thermal tolerance is often neglected. This study examined the ability of the trematode Podocotyle atomon to modulate the feeding and stress response of Gammarus locusta towards temperature. To accomplish this, infected and uninfected females and males of Gammarus locusta were exposed to temperatures (2, 6, 10, 14, 18, 22, 26, 30 °C) for six days. Shredding (change in food biomass) and defecation rates (as complementary measure to shredding rate) were measured as proxies for feeding activity. Lipid and glycogen concentrations (energy reserves), catalase (oxidative stress indicator), and phenoloxidase (an immunological response in invertebrates) were additionally measured. Gammarid survival was optimal at 10 °C as estimated by the linear model and was unaffected by trematode infection. Both temperature and sex influenced the direction of infection effect on phenoloxidase. Infected females presented lower phenoloxidase activity than uninfected females at 14 and 18 °C, while males remained unaffected by infection. Catalase activity increased at warmer temperatures for infected males and uninfected females. Higher activity of this enzyme at colder temperatures occurred only for infected females. Infection decreased lipid content in gammarids by 14 %. Infected males had significantly less glycogen than uninfected, while infected females showed the opposite trend. The largest infection effects were observed for catalase and phenoloxidase activity. An exacerbation of catalase activity in infected males at warmer temperatures might indicate (in the long-term) unsustainable, overwhelming, and perhaps lethal conditions in a warming sea. A decrease in phenoloxidase activity in infected females at warmer temperatures might indicate a reduction in the potential for fighting opportunistic infections. Results highlight the relevance of parasites and host sex in organismal homeostasis and provide useful insights into the organismal stability of a widespread amphipod in a warming sea.

Description: We interpret the crustal and upper mantle structure along ∼2500 km long seismic profiles in the northeastern part of the Sino-Korean Craton (SKC). The seismic data with high signal-to-noise ratio were acquired with a nuclear explosion in North Korea as source. Seismic sections show several phases including Moho reflections (PmP) and their surface multiple (PmPPmP), upper mantle refractions (P), primary reflections (PxP, PL, P410), exceptionally strong multiple reflections from the Moho (PmPPxP), and upper mantle scattering phases, which we model by ray-tracing and synthetic seismograms for a 1-D fine-scale velocity model. The observations require a thin crust (30 km) with a very low average crustal velocity (ca. 6.15 km/s) and exceptionally strong velocity contrast at the Moho discontinuity, which can be explained by a thin Moho transition zone (〈 5 km thick) with strong horizontal anisotropy. We speculate that this anisotropy was induced by lower crustal flow during delamination dripping. An intra-lithospheric discontinuity (ILD) at ∼75 km depth with positive velocity contrast is probably caused by the phase transformation from spinel to garnet. Delayed first arrivals followed by a long wave train of scattered phases of up to 4 s duration are observed in the 800–1300 km offset range, which are modelled by continuous stochastic velocity fluctuations in a low-velocity zone (LVZ) below the Mid-Lithospheric Discontinuity (MLD) between 120 and 190 km depth. The average velocity of this LVZ is about 8.05 km/s, which is much lower than the IASP91 standard model. This LVZ is most likely caused by rocks which are either partially molten or close to the solidus, which explains both low velocity and the heterogeneous structure.

Description: Europe has experienced a substantial increase in non-indigenous crayfish species (NICS) since the mid-20th century due to their extensive use in fisheries, aquaculture and, more recently, pet trade. Despite relatively long invasion histories of some NICS and negative impacts on biodiversity and ecosystem functioning, large spatio-temporal analyses of their occurrences are lacking. Here, we used a large freshwater macroinvertebrate database to evaluate what information on NICS can be obtained from widely applied biomonitoring approaches and how usable such data is for descriptions of trends in identified NICS species. We found 160 time-series containing NICS between 1983 and 2019, to infer temporal patterns and environmental drivers of species and region-specific trends. Using a combination of meta-regression and generalized linear models, we found no significant temporal trend for the abundance of any species (Procambarus clarkii, Pacifastacus leniusculus or Faxonius limosus) at the European scale, but identified species-specific predictors of abundances. While analysis of the spatial range expansion of NICS was positive (i.e. increasing spread) in England and negative (significant retreat) in northern Spain, no trend was detected in Hungary and the Dutch-German-Luxembourg region. The average invasion velocity varied among countries, ranging from 30 km/year in England to 90 km/year in Hungary. The average invasion velocity gradually decreased over time in the long term, with declines being fastest in the Dutch-German-Luxembourg region, and much slower in England. Considering that NICS pose a substantial threat to aquatic biodiversity across Europe, our study highlights the utility and importance of collecting high resolution (i.e. annual) biomonitoring data using a sampling protocol that is able to estimate crayfish abundance, enabling a more profound understanding of NICS impacts on biodiversity.

Description: Defining a precise timeline for past eruptions from explosive volcanoes in continental arcs is imperative to forecast future hazards and mitigate volcanic disasters in these often densely populated regions. However, establishing reliable ages for Quaternary eruptions in the Central American Volcanic Arc has been challenging due to the common lack or alteration of suitable K-rich phases for 40Ar/39Ar geochronology, but also from their position in time beyond the reach of 14C dating. This especially holds for the active Amatitlán caldera in Guatemala, from which at least six explosive silicic eruptions have produced tephra blanketing neighboring regions that are today inhabited by millions of people. Zircon, a common datable accessory mineral in Amatitlán caldera magmas, is used here to retrieve eruption ages by applying the novel zircon double-dating method (ZDD) that integrates 238U–230Th disequilibrium dating and (U–Th)/He thermochronology. This approach yielded the first-ever radioisotopic ages of 24 ± 3 ka and 48 ± 6 ka (1σ), respectively, of two of Amatitlán caldera's most recent eruptions (J-tephra and E-tephra). Remarkably, both zircon crystallization and ZDD eruption ages for the older and voluminous T-tephra and L-tephra units significantly post-date existing plagioclase 40Ar/39Ar dates by ca. 26 and 70 kyr, respectively. The ZDD eruption age for T-tephra is 93 ± 4 ka, whereas zircon crystallization ages for L-tephra yield a maximum model eruption age of ca. 124 ka. The strong eruption age divergence between ZDD and plagioclase 40Ar/39Ar dating argues for the presence of inherited or xenocrystic plagioclase in Amatitlán caldera eruptive products. Statistical analysis based on the updated eruptive history suggests a recurrence interval of ca. 17 kyr, which is significantly shorter than previously estimated. The new age data, thus, suggest a more frequent eruptive activity of Amatitlán caldera than formerly thought and underscores the necessity to better understand the current underlying magmatic system and to constrain its past eruptive history more precisely.

Description: The Carpathian-Pannonian Region (CPR) hosted some of the largest silicic volcanic eruptions in Europe during the Early and Middle Miocene, contemporaneously with major lithospheric thinning of the Pannonian Basin. This was recorded as an ignimbrite flare-up event from approximately 18.1–14.4 Ma. To gain in-depth perspectives on the eruption chronology, tephrostratigraphy, and petrogenesis at the onset of CPR silicic volcanism, we applied a multi-proxy approach to Lower Miocene rhyolitic ignimbrites and pyroclastic fall deposits from the northern CPR to the Dinaride Lake System. High-precision zircon U-Pb geochronology distinguished two Lower Miocene groups of volcaniclastic rocks at ∼ 18.1 Ma and ∼ 17.3 Ma. Based on combined tephrostratigraphic signatures we propose that the ∼ 18.1 Ma Kalnik and ∼ 17.3 Ma Eger eruptions produced widespread (intermediate to) large caldera-forming massive rhyolitic ignimbrites, deposited across northern and southwestern regions of the CPR. Due to easterly winds that carried volcanic ash hundreds of kilometers to the southwest, Eger eruption products also reached distal intra-montane Dinaride lacustrine basins, recorded as pyroclastic fall deposits. Heterogeneous major and trace elemental compositions of ∼ 18.1 Ma volcanic glass shards suggest that the Kalnik eruption was sourced from complex silicic magmatic systems, with simultaneous tapping of two discrete melt bodies during the eruption. The homogeneous geochemical composition of ∼ 17.3 Ma glasses is distinct from the older glasses. Integrated zircon and bulk glass Nd-Hf isotope compositions have a positive correlation, defining a regional mantle array, and are more radiogenic in the younger phase of volcanism. The recorded systematic isotopic change, moving from older more crustal signatures to younger more juvenile compositions, imply that during the period of lithospheric thinning of the Pannonian Basin the region underwent more complex variations in the interaction between metasomatized lithospheric mantle-derived magmas and various crustal components than previously recognized.

Description: Highlights: • Silicoflagellates more common and diverse in late Eocene, lower in Oligocene. • Record of new species Corbisema tajmahalii from Late Eocene, with interpreted double skeleton (DS). • First known Bachmannocena DS, has corner-aligned configuration. • Observation of early evolution of Stephanocha raupii, transferred to Distephanopsis. Abstract Study of the South Pacific Ocean sediments from IODP Expedition 378, Holes U1553A and U1553B, shows 19 late Eocene to late Oligocene silicoflagellate species. The late Eocene includes Corbisema tajmahalii n. sp., observed over a ∼ 8.4 m interval and proposed as a new subzone within the Corbisema apiculata Zone. The new species is characterized by the presence of basal ring that has three sides and an arrowhead-shaped outline with the two minor-axis corners more closely spaced. This study has found the first known Bachmannocena double skeleton, in corner-aligned configuration that suggests evolutionary relationship with the Corbisema triacantha group of Cenozoic silicoflagellates. Also observed is the apparent early evolution of Stephanocha raupii at ∼29.6 Ma, derived from a skeletal diversity related to Distephanopsis crux, thus the species is here transferred to Distephanopsis (abbreviated as Ds.). Silicoflagellate skeletal abundance declines after the Eocene-Oligocene boundary, with generally low abundance except for two sediment samples immediately below the Ds. raupii n. comb. first appearance.

Description: Dissolved (〈0.2 μm) trace metals (dTMs) including iron (Fe), manganese (Mn), and cobalt (Co) are micronutrients that (co-) limit phytoplankton growth in many ocean regions. Here, we present the spatial and seasonal distributions of dFe, dMn, and dCo on the Northeast Atlantic continental margin (Celtic Sea), along a transect across the shelf and two off-shelf transects along a canyon and a spur. Waters on the continental shelf showed much higher dTM concentrations (dFe 0.07–6.50 nmol L−1, average 1.41 ± 0.96 nmol L−1, n = 138; dMn 0.868–14.8 nmol L−1, 2.75 ± 2.37 nmol L−1, n = 148; dCo 54.8–217 pmol L−1, 109 ± 32 pmol L−1, n = 144) than on the slope (dFe 0.03–1.90 nmol L−1, 0.65 ± 0.43 nmol L−1, n = 454; dMn 0.223–1.14 nmol L−1, 0.58 ± 0.20 nmol L−1, n = 458; dCo 27.3–122 pmol L−1, 71.7 ± 11.7 pmol L−1, n = 441), attributed to strong dTM contributions from a low-salinity endmember, i.e., riverine discharge. Benthic sedimentary input via reductive dissolution (especially for dFe and dMn), delineated by short-lived radium (Ra) isotopic activities (223Raxs and 224Raxs), was only prominent at a station (Site A) characterized by fine sediments. On the continental slope, dMn levels at depth were mainly determined by the formation of insoluble Mn oxides and the intrusion of Mediterranean Outflow Waters. In contrast, dFe and dCo concentrations at depth were balanced by the regeneration from remineralization of sinking organic particles and scavenging removal. In addition, bottom and intermediate nepheloid layers along the slope illustrated both elevated dTM concentrations and Ra isotopic activities. The presence of nepheloid layers is especially significant along the canyon transect relative to the spur transect, demonstrating the importance of slope topography on the off-shelf transport of dTMs into the Northeast Atlantic Ocean. As a seasonal stratified shelf sea, dTMs and nutrients showed synchronized seasonal variations on the shelf, indicating the influence of biological processes in addition to source effects. Surface dFe and dCo were depleted in summer due to enhanced biological uptake, while sub-surface dFe and dCo were elevated in summer and autumn ascribed to the remineralization of sinking organic particles. In contrast, surface dMn levels were predominantly controlled by the seasonal variations in photoreduction, while sub-surface dMn concentrations were relatively constant throughout the year. The combined effects of fluvial and benthic sources, topographical controls, and biological processes shape the seasonal variations of dTM distributions. Such seasonal variations in dTMs and biological activities can affect the biological carbon pump on the Northeast Atlantic continental margin, and may further influence the carbon cycle in the Atlantic Ocean via the dynamic dTM exchange between continental margins and the open ocean.

Description: Improving the quantitative performance of mass spectrometry (MS)-based metabolomics is the key to its successful application in a broad range of research questions. Like other analytical pipelines, there are quantitative challenges in metabolomics. In particular, due to the large amount of data generated from MS, metabolomics data present unique quantitative challenges that conventional wet-lab approaches cannot address. Complementary bioinformatic methods exhibit unique advantages in tackling these problems. However, analytical chemists often underestimate the importance of bioinformatic solutions in the era of omics. This review summarizes the critical quantitative challenges in MS-based metabolomics. It highlights the existing bioinformatic solutions and discusses ongoing issues as future directions for method development. A specific focus is given to liquid chromatography-mass spectrometry (LC-MS)-based metabolomics because of its wide usage. Through this review, we hope to encourage awareness of the existing quantitative biases and their bioinformatic solutions. We also hope to motivate the development of bioinformatic methods for accurate, precise, and robust quantitative metabolomics.

Description: The mussel Mytilus edulis, a host to various trematode species, experiences performance decrements due to these infections. Yet, the impact magnitude and potential interactions with environmental stressors remain largely unexplored. This study scrutinizes the effect of Renicola roscovita infections on mussel filtration and respiration. We first assessed performance in both uninfected and lab-infected mussels at a mild temperature (16 °C), following an acute heat ramp to 30.5 °C and subsequent cooling. The experiment revealed neither a significant direct impact of the infection on the mussels' performance, nor any significant interplay between the infection and temperature variations. To account for possible infection effects obscured by low sample sizes or mussel size disparities, we conducted a reassessment at 16 °C using both small and large mussels. Infection notably hampered filtration in large mussels, with a marginal impact on smaller ones. A positive correlation was found between infection intensity and mussel filtration capacity, though the infection had no discernible impact on respiration. Our consistent finding of an 11-12 % infection effect size across all experiments indicates a slight reduction in mussel filtration due to trematode infections. While the exacerbating effect of transient heat stress on the infection's impact on filtration was not statistically significant, future investigations should explore potential interactions with prolonged heat stress. Our findings underscore the nuanced ways in which parasitic infections can influence marine bivalve physiology, emphasizing the need for more comprehensive studies that incorporate environmental stressors, such as heat stress, to fully elucidate the impact of parasitism on marine ecosystem health and resilience.

Description: Waterborne pathogenic bacteria, including faecal indicator bacteria and potentially pathogenic Vibrio, are a global concern for diseases transmitted through water. A systematic review was conducted to analyse publications that investigated these bacteria in relation to macrophytes (seagrasses and macroalgae) in coastal marine environments. The highest quantities of FIB were found on brown algae and seagrasses, and the highest quantities of Vibrio bacteria were on red algae. The most extensively studied macrophyte group was brown algae, green algae were the least researched. Macrophyte wrack was found to favor the presence of FIB, but there is a lack of information about Vibrio quantities in this environment. To understand the role of Vibrio bacteria that are pathogenic to humans, molecular methods complementary to cultivation methods should be used. Further research is needed to understand the underlying mechanisms of FIB and potentially pathogenic Vibrio with macrophytes and their microbiome in the coastal marine environment.

Description: Mercury (Hg) fulminate was used as a primary fuse in World War (WW) munitions, and may consequently be a Hg source for impacted environments. Mercury is a conspicuous and persistent pollutant, with methylmercury (MeHg) acting as a notorious neurotoxin. Considerable amounts of munitions were intentionally dumped in the North Sea and Baltic Sea following the First and Second WWs. After more than 70 years on the seafloor many munitions have corroded and likely release explosive compounds, including Hg fulminate. The Germany coastal city of Kiel was a manufacturing centre for submarines, and accordingly a prominent target for bombing and post-war disarmament. We collected water and sediment samples around Kiel Bay to assess regional levels and quantify any Hg contamination. The munition dump site Kolberger Heide (KH) and a former anti-aircraft training center Dänisch-Nienhof are situated in Kiel Bay, and were targeted for sampling. Sediment Hg concentrations around KH were notably elevated. Average Hg concentrations in KH sediments were 125 ± 76 ng/g, compared to 14 ± 18 ng/g at background (control) sites. In contrast, dissolved Hg in the water column exhibited no site variations, all ranging between 0.8 and 2.1 pM. Methylmercury in sediments and waters did not have enhanced concentrations amongst sites (〈30 pg/g and 〈50 fM, respectively). Sediment-water exchange experiments showed elevated Hg and MeHg fluxes (i.e. 〉400 pmol m−2 d−1 MeHg) at one KH location, however remaining cores had low to no Hg and MeHg output (〈0–27 pmol m−2 d−1 MeHg). Thus, sediments in Kiel Bay proximate to WW munitions could harbor and form a source of Hg, however water column mixing and removal processes attenuate any discharge from the seafloor to overlying waters.

Description: The Peruvian upwelling zone is one of the most productive marine ecosystems in the world with a spectacular, pronounced oxygen minimum zone (OMZ). Globally OMZs are increasing in size and intensity with far-reaching consequences for the marine biological carbon pump and carbon export; thus, these zones need to be carefully monitored to be able to understand future climate change impacts. The current study was carried out in 2013 and 2017 to quantify the vertical flux of organic matter exported out of the productive surface layer by measuring 234Thsingle bond238U disequilibria in the water column. Samples were collected in January 2013 and May 2017 along an identical transect located at 12°S off the Peruvian coast near Lima, Peru. Th-234 fluxes ranged from 0 to 2088 ± 95 dpm m−2 d−1 in 2013 and 698 ± 63 to 3648 ± 113 dpm m−2 d−1 in 2017. The corresponding POC fluxes varied between 0 and 164.2 ± 7.9 mg C m−2 d−1 in 2013 and 22.7 ± 2.7 to 133.1 ± 15.2 mg C m−2 d−1 in 2017, with POC fluxes gradually decreasing with distance from the coast. Despite higher POC fluxes, the export efficiencies were found to be extremely low due to high particle remineralization rates observed within the euphotic zone.

Description: Background Prostate cancer (PCa) patients treated with androgen deprivation therapy (ADT) have an increased fracture risk. Exploring biomarkers for early bone loss detection is of great interest. Methods Pre-planned substudy of the ARNEO-trial (NCT03080116): a double blind, randomised, placebo -controlled phase 2 trial performed in high-risk PCa patients without bone metastases between March 2019 and April 2021. Patients were 1:1 randomised to treatment with gonadotropin-releasing hormone antagonist (degarelix) + androgen receptor signalling inhibitor (ARSI; apalutamide) versus degarelix + matching placebo for 12 weeks prior to prostatectomy. Before and following ADT, serum and 24-h urinary samples were collected. Primary endpoints were changes in calcium-phosphate homeostasis and bone biomarkers. Findings Of the 89 randomised patients, 43 in the degarelix + apalutamide and 44 patients in the degarelix + placebo group were included in this substudy. Serum corrected calcium levels increased similarly in both treatment arms (mean difference +0.04 mmol/L, 95% confidence interval, 0.02; 0.06), and parathyroid hormone and 1,25-dihydroxyvitamin D3 levels decreased. Bone resorption markers increased, and stable calcium isotope ratios reflecting net bone mineral balance decreased in serum and urine similarly in both groups. Interpretation This exploratory substudy suggests that 12 weeks of ADT in non-metastatic PCa patients results in early bone loss. Additional treatment with ARSI does not seem to more negatively influence bone loss in the early phase. Future studies should address if these early biomarkers are able to predict fracture risk, and can be implemented in clinical practice for follow-up of bone health in PCa patients under ADT.

Description: The Lausitz Block, located in the northernmost part of the Bohemian Massif, hosts a large number of dike- to stock-shaped gabbroic intrusions that mainly comprise brown hornblende-poor (Group I; i.e. olivine gabbronorite, olivine gabbro, gabbro and diorite) and subordinately brown hornblende-rich lithologies (Group II; i.e. olivine-hornblende gabbro and hornblende gabbro). Several of these intrusions host small-scaled magmatic Ni-Cu-(PGE) sulfide accumulations. The intrusions are part of an interconnected mafic–(ultramafic) plumbing system that intruded Cadomian granodiorites of Lausitz Block in the Middle to Late Devonian during the early stages of the Variscan Orogeny. The previously inferred Devonian age of the intrusions is refined by biotite Ar-Ar dating that yield ages between 372.2 ± 3.7 Ma and 389.1 ± 3.9 Ma (2σ). Group I and Group II lithologies differ in their mineralogical and geochemical composition. Compared to the Group I lithologies those of Group II are characterized by higher modal contents of primary brown hornblende, Fe-Ti oxides and apatite, by Ti- and Al-enriched clinopyroxene and by lower contents of SiO 2 and increased contents of TiO 2 , P 2 O 5 , LILE, HFSE and LREE. The differences suggest at least two different magmatic series where Group I rocks are linked to tholeiitic basaltic magmas with low to moderate Ti and volatile contents, whereas Group II rocks are derived from Ti- and volatile-enriched moderate-alkaline basaltic magmas. The magmas experienced clinopyroxene fractionation during their crustal ascent and storage, but were only minor affected by crustal contamination (〈 5 %) according to Sr-Nd-Pb isotope systematics. Clinopyroxene and whole-rock trace element compositions suggest that primary magmas of both series are linked to an intraplate setting. REE systematics suggest primary magma contributions from both garnet and spinel peridotite sources. Group II samples bear evidence for higher proportions of garnet peridotite-derived melts, and trace element modelling indicates melting degrees between ~5–20 % for both groups. The proposed intraplate magmatism is might been related to a subduction slab retreat within the framework of the Variscan orogeny, which leads to lithosphere extension and enhanced decompression melting of the mantle beneath the Lausitz Block. Cu/Zr ratios 〈 1 of gabbroic rocks from several intrusions suggest a previous segregation of magmatic sulfides in other sections of the magmatic plumbing system and give rise for a vertical and lateral Ni-Cu exploration potential.

Description: Marine environments are globally impacted by vast quantities of munition disposed following both World Wars. Dumped munitions contain conventional explosives, chemicals warfare agents as well as a variety of metals. Field monitoring studies around marine dumpsites report the presence of munition constituents in water and sediment samples. The growing interest and developments in the ocean as a new economic frontier underline the need to remediate existing dumpsites. Here, we provide a comprehensive assessment of the magnitude and potential risks associated with marine munition dumpsites. An overview of the global distribution of dumpsites identifying the most impacted areas is provided, followed by the currently available data on the detection of munition constituents in environmental samples and evidence of their toxic potential to human and environmental health. Finally, existing data gaps are identified and future research needs promoting better understanding of the impact of the dumped material on the marine environment suggested.

Description: Concentrations of particulate organic carbon (POC) and total hydrolyzable amino sugars (THAS) were measured along a transect of the dynamic South Yellow Sea (SYS) to investigate the bioreactivity and bacterial reworking of particulate organic matter (POM). Results showed that POM bioavailability was linked with primary production, as revealed by the significant correlation between chlorophyll-a concentrations and the diagenetic indicator glucosamine/galactosamine (GlcN/GalN). Production of bioavailable POM could rapidly stimulate microbial activity, generating hot spots of heterotrophic alteration. Lower GlcN/GalN ratios (〈3) observed in the entire SYS indicate that POM underwent extensive microbial alteration. In particular, extremely low GlcN/GalN ratios (∼0.7) were found in the Yellow Sea Cold Water Mass, reflecting high bacterial alteration of POM. Estimates based on the bacterial biomarker muramic acid showed that on average ∼13% of POM in the SYS was of bacterial origin. Elevated bacterial contributions were found in both nearshore and offshore areas. Strong mixing in the nearshore and the presence of cyclonic eddies in offshore waters may increase the residence time of POM in the water column and thus promote bacterial transformation of POM. Overall, our findings indicate that bacterial reworking of POM varies with productivity and that the extensive bacterial transformation of the remaining POM observed in the water column probably enhances long-term carbon sequestration.

Description: Highlights • the western Ionian Basin shows three distinct canyon-channel systems. • 〉140 m-thick gravity flow along main passageway in the east; velocity 5–6 m s−2. • numerous erosional and depositional bedforms (e.g., scours, sediment waves). • north-eastern Sicily and southern Calabria are potential source areas. • main failure likely offshore between San Leo and Bocale (southern Calabria). Abstract Earthquakes, tsunamis and gravity flows are common processes offshore Eastern Sicily and pose a significant hazard to coastal communities and infrastructure. The 1908 Messina earthquake and tsunami resulted in 〉60,000 casualties. It caused a large turbidity current, which broke the Malta-Zante telegraph cable. Yet, this gravity flow remains poorly characterised in terms of its route and flow behaviour. A comprehensive analysis of multibeam echosounder data, sub-bottom profiles, and sediment cores has been carried out to improve our understanding about gravity flow activity within conduit systems of the western Ionian Basin to reconstruct the characteristics of the 1908 sediment flow (e.g., erosion, velocity, source region). Three main canyon-channel systems can be distinguished within the study area. The easternmost system (C3) appears to be the most active in terms of sediment transport. There are numerous erosional and depositional bedforms, including large-scale scours (〉100 m-long), turbidite sediment waves and channel wall collapses that are not overprinted by younger events. The other two canyon-channel systems (C1, C2) do not show many bedforms indicative of repeated and recent gravity flow activity. Indeed, the transport of the majority of sediment discharged into the western system (C1) is limited to 〈25 km downslope from the continental slope, while the central system (C2) facilitates sediment deposition from gravity flows. C3 is, thus, suggested to have been the main passageway of the 1908 sediment flow. It also leads directly to two of three cable break locations. The most likely source areas for the gravity flow are north-eastern Sicily and southern Calabria. Bedforms indicate a flow thickness of 〉170 m along the upper channel portion of C3 and 〉 140 m along its lower portion close to the cable breaks. An average flow velocity of 5.6 to 6.3 ms−1 is reconstructed, given the timing of the breaks and length of the canyon-channel system. The flow may have locally decelerated and accelerated while bypassing morphologic highs and knickpoints. These new findings significantly improve our understanding of the 1908 gravity flow (e.g., passageways, depositional/erosional behaviour, thickness, velocity) and provide important insights into gravity flow events in general, especially those with a large run-out. This knowledge is needed to assess potential hazards associated with these events.

Description: A suite of fresh and variably phosphatized submarine volcanic rock samples from NW Pacific seamounts from the Mid Cretaceous were subject of a detailed trace element and isotopic leaching study to examine the effect of phosphate alteration on the use of Sr-, Nd-, and Pb- radiogenic isotope systems. The study particularly focuses on the behavior of the respective parent/daughter element pairs during phosphatization and leaching in order to evaluate the impact on radiogenic ingrowth correction (“age correction”) for old seafloor samples and their use in geochemical studies. For this purpose, variably intense leaching procedures (no leaching; 2 M HCl at 70 °C for 1 h; 6 M HCl at 130 °C for 3 h) were applied to diverse sample materials (rock powder, rock chips and fresh volcanic glass chips). Phosphatization causes significant modification of isotope ratios and elemental proportions of most trace elements including the rare earth elements. As opposed to common seafloor weathering, Rb/Sr decreases in the lavas with increasing phosphatization, while U/Pb enrichment appears slightly amplified. Mild acid leaching of rock chips, however, generally yields Sr, Nd and Pb isotope ratios largely in accordance with values from fresh glass fractions of the same samples and comparable with the results for similarly leached rock powders. Applying original (non-leached) elemental concentration ratios for the radiogenic age correction of mildly leached sample chips produces mixed results for 87Sr/86Srin but generally agrees with expected 143Nd/144Ndin, 206Pb/204Pbin, 207Pb/204Pbin, and 208Pb/204Pbin values. All residua of strongly leached powders yield significantly more radiogenic 206Pb/204Pbm, 143Nd/144Ndm and higher U/Pb than mildly leached rock chips or powders or even non-leached powder of the respective samples, opposite to what is expected when removing seawater-derived secondary phases by stronger acid leaching. We suggest that this enrichment, after removal of most of the magmatic Pb and Nd, reflects minor refractory components that formed in association with the phosphatization and developed high 206Pb/204Pb ratios by radiogenic ingrowth since the eruption of these lavas in the Mid Cretaceous due to high U/Pb. Utilizing modeled parent/daughter ratios based on magma evolution systematics of associated fresh glass yields no satisfying initial isotopic compositions for the strongly leached samples despite supposed removal of secondary isotopic signals upon leaching. Applying the modeled parent/daughter ratios to age correct mildly leached sample chips and powder otherwise slightly improves the accordance with their respective fresh glass fractions for 208Pb/204Pbin but yields similar results as if using the actual parent/daughter ratios for 143Nd/144Ndin, 86Sr/87Srin, 206Pb/204Pbin, and 207Pb/204Pbin.

Description: Microplastics are substrates for microbial activity and can influence biomass production. This has potentially important implications in the sea-surface microlayer, the marine boundary layer that controls gas exchange with the atmosphere and where biologically produced organic compounds can accumulate. In the present study, we used six large scale mesocosms to simulate future ocean scenarios of high plastic concentration. Each mesocosm was filled with 3 m3 of seawater from the oligotrophic Sea of Crete, in the Eastern Mediterranean Sea. A known amount of standard polystyrene microbeads of 30 μm diameter was added to three replicate mesocosms, while maintaining the remaining three as plastic-free controls. Over the course of a 12-day experiment, we explored microbial organic matter dynamics in the sea-surface microlayer in the presence and absence of microplastic contamination of the underlying water. Our study shows that microplastics increased both biomass production and enrichment of carbohydrate-like and proteinaceous marine gel compounds in the sea-surface microlayer. Importantly, this resulted in a ∼3 % reduction in the concentration of dissolved CO2 in the underlying water. This reduction was associated to both direct and indirect impacts of microplastic pollution on the uptake of CO2 within the marine carbon cycle, by modifying the biogenic composition of the sea's boundary layer with the atmosphere.

Description: Iron (Fe) speciation in marine sediments and suspended particulate matter (SPM) are widely used to investigate the role of Fe minerals in marine biogeochemical cycling and to reconstruct paleo-redox conditions. A traditional method for the determination of Fe speciation are sequential extractions, in which operationally defined Fe pools are dissolved by specific extraction solutions. More recently, many studies make use of synchrotron radiation-based X-ray absorption near edge spectroscopy (XANES), especially if little sample material is available or a high spatial resolution is required. However, few studies have systematically compared Fe speciation obtained by the two methods. Here, we report Fe speciation for marine sediments (both wet and freeze-dried) and SPM from contrasting marine environments (western Baltic Sea and Amazon shelf) obtained by sequential extraction and XANES. The two methods yield comparable results regarding the approximate proportion of reactive Fe ((oxyhydr)oxides, carbonate and sulfide minerals) in the total Fe pool and the extent to which reactive Fe minerals have been converted to pyrite. However, methodological issues associated with both approaches complicate a direct comparison of specific mineral groups. Pyrite concentrations obtained by XANES are lower than those obtained by extraction, which is attributed to an underestimation by XANES due to self-absorption effects and an overestimation by the chromium reduction method due to dissolution of reduced sulfur phases that are not associated with Fe. As substantial amounts of pyrite are oxidized during freeze-drying and sample storage, we recommend to analyze wet sediments in modern marine environments. The XANES spectra of Fe (oxyhydr)oxide and Fe(III)-containing (ferric) clay minerals are similar, which is why these components cannot be differentiated by XANES. Similarly, sequential extraction schemes are known to dissolve a variable proportion of ferric clay minerals along with Fe carbonates and Fe (oxyhydr)oxides. Further investigating the role of ferric clay minerals in the low-temperature marine Fe cycle may therefore require the use of additional methods. Our findings may help to assess the transferability of XANES-based Fe speciation for small sediment and SPM samples to those reported in more traditional studies on Fe biogeochemical cycling and paleo-redox conditions.

Description: Many capture fisheries are considered data-poor, including the northern pike (Esox lucius) fishery in brackish lagoons in the southern Baltic Sea of Germany. The objective of our work was to assess the exploitation status of this stock, which is perceived by stakeholders to be in decline. Size structure data collected via rod-and-reelangling, fyke nets, and gill nets, and empirical estimates of growth, maturation, and fecundity from the lagoon stock were used to fit the Length-Based Spawning Potential Ratio (LB-SPR) model. Parameter uncertainty in von Bertalanffy growth estimates and natural mortality in the Baltic Sea pike stock was considered in sensitivity analyses. Assessment outcomes were sensitive to estimates of growth rate, particularly asymptotic length L infinity, instantaneous natural mortality M, and gear selectivity. Under-aging of old fish in scale-based age estimates overestimated terminal length and generated negative bias in the estimated stock status. Despite the sensitivity of assessment outcomes to life-history parameter choice, the stock status for the Baltic Sea consistently indicated a fully exploited situation with SPRs robustly above 0.4 and current fishing mortality rates between 0.2 and 0.4 yr-1. This result agreed with previous assessments using catch-only models. Our work serves as a reminder, that when using length-based methods, unbiased growth, and natural mortality estimates are critical for robust assessment outcomes.

Description: The Valle del Bove is a profound and wide scar on the east Etna flank witnessing the Holocene main volcano-tectonic event of the volcano, frequently invaded by lava flows during the last centuries. The Valle del Bove slope failure produced the Milo debris avalanche deposit on the lower east flank that is partially covered by the Mongibello lavas and a pyroclastic succession. In this paper, we constrain for the first time the age of the Milo debris avalanche deposit and the overlying lava succession exposed at three quarries recently caved at the valley mouth through a multidisciplinary approach integrating stratigraphic and petrographic analyses, 14C, and paleomagnetic dating. In particular, 14C age determinations of the Milo debris avalanche deposit indicate that the initial stage of the catastrophic flank collapse of the Valle del Bove occurred at 7478–7134 BCE during the Mesolithic age. Conversely, the main portion of the lava succession filling the valley floor emplaced after the sub-Plinian picritic eruption occurred at 2579–2278 BCE (FS tephra layer) consistently with the increasing occurrence frequency of flank eruptions documented in the geological record of Etna during the past 4000 yrs. Paleomagnetic dating highlighted that in the study area the sub-Plinian eruption was followed by two quasi-contemporaneous flank eruptions during the Late Copper age (2600–2400 BCE), whereas other two flank eruptions occurred during Greek-Roman and Medieval ages. These results have relevant implications on the stratigraphy and evolution of Etna, particularly on the Valle del Bove initial collapse and the relative emplacement of the Chiancone detritic-alluvial sequence.

Description: The role of macroalgae (seaweed) as a global contributor to carbon drawdown within marine sediments – termed ‘blue carbon’ – remains uncertain and controversial. While studies are needed to validate the potential for macroalgal‑carbon sequestration in marine and coastal sediments, fundamental questions regarding the fate of dislodged macroalgal biomass need to be addressed. Evidence suggests macroalgal biomass may be advected and deposited within other vegetated coastal ecosystems and down to the deep ocean; however, contributions to near-shore sediments within coastal waters remain uncertain. In this study a combination of eDNA metabarcoding and surficial sediment sampling informed by seabed mapping from different physical environments was used to test for the presence of macroalgal carbon in near-shore coastal sediments in south-eastern Australia, and the physical factors influencing patterns of macroalgal transport and deposition. DNA products for a total of 68 macroalgal taxa, representing all major macroalgal groups (Phaeophyceae, Rhodophyta, and Chlorophyta) were successfully detected at 112 near-shore locations. These findings confirm the potential for macroalgal biomass to be exported into near-shore sediments and suggest macroalgal carbon donors could be both speciose and diverse. Modelling suggested that macroalgal transport and deposition, and total organic carbon (TOC), are influenced by complex interactions between several physical environmental factors including water depth, sediment grain size, wave orbital velocity, current speed, current direction, and the extent of the infralittoral zone around depositional areas. Extrapolation of the optimised model was used to predict spatial patterns of macroalgal deposition and TOC across the coastline and to identify potentially important carbon sinks. This study builds on recent studies providing empirical evidence for macroalgal biomass deposits in near-shore sediments, and a framework for predicting the spatial distribution of potential carbon sinks and informing future surveys aimed at determining the potential for long-term macroalgal carbon sequestration in marine sediments.

Description: Highlights • Nutrient and carbon fluxes are key processes in land-ocean interactions. • We sampled along the river-estuary-ocean system according to travel time of water. • The river was autotrophic with phytoplankton growth, high pH and oxygen concentration, and CO2 undersaturation. • Phytoplankton died off in the estuary causing low pH and oxygen concentration, CO2 supersaturation, and nutrient release. • The approach is suitable to investigate single events such as hydrological extremes. Nutrient and carbon dynamics within the river-estuary-coastal water systems are key processes in understanding the flux of matter from the terrestrial environment to the ocean. Here, we analysed those dynamics by following a sampling approach based on the travel time of water and an advanced calculation of nutrient fluxes in the tidal part. We started with a nearly Lagrangian sampling of the river (River Elbe, Germany; 580 km within 8 days). After a subsequent investigation of the estuary, we followed the plume of the river by raster sampling the German Bight (North Sea) using three ships simultaneously. In the river, we detected intensive longitudinal growth of phytoplankton connected with high oxygen saturation and pH values and an undersaturation of CO2, whereas concentrations of dissolved nutrients declined. In the estuary, the Elbe shifted from an autotrophic to a heterotrophic system: Phytoplankton died off upstream of the salinity gradient, causing minima in oxygen saturation and pH, supersaturation of CO2, and a release of nutrients. In the shelf region, phytoplankton and nutrient concentrations were low, oxygen was close to saturation, and pH was within a typical marine range. Over all sections, oxygen saturation was positively related to pH and negatively to pCO2. Corresponding to the significant particulated nutrient flux via phytoplankton, flux rates of dissolved nutrients from river into estuary were low and determined by depleted concentrations. In contrast, fluxes from the estuary to the coastal waters were higher and the pattern was determined by tidal current. Overall, the approach is appropriate to better understand land-ocean fluxes, particularly to illuminate the importance of these fluxes under different seasonal and hydrological conditions, including flood and drought events.

Description: Highlights: • DNA variation is characterized for aspartate aminotransferase allozymes in snails. • Allozyme alleles differ by 2–4 substitutions. • Aspartate aminotransferase is expressed in the snail at the constant level. • Aspartate aminotransferase gene is present in the snail genome in multiple copies. Abstract: Allozymes present several classical examples of divergent selection, including the variation in the cytosolic aspartate aminotransferase (AAT) in the intertidal snails Littorina saxatilis. AAT is a part of the asparate-malate shuttle, in the interidal molluscs involved in the anaerobic respiration during desiccation. Previous allozyme studies reported the sharp gradient in the frequencies of the AAT100and the AAT120 alleles between the low and high shores in the Northern Europe and the differences in their enzymatic activity, supporting the role of AAT in adaptation to desiccation. However, the populations in the Iberian Peninsula showed the opposite allele cline. Using the mRNA sequencing and the genome pool-seq analyses we characterize DNA sequences of the different AAT alleles, report the amino acid replacements behind the allozyme variation and show that same allozyme alleles in Northern and Southern populations have different protein sequences. Gene phylogeny reveals that the AAT100 and the northern AAT120 alleles represent the old polymorphism, shared among the closely related species of Littorina, while the southern AAT120 allele is more recently derived from AAT100. Further, we show that the Aat gene is expressed at constitutive level in different genotypes and conditions, supporting the role of structural variation in regulation of enzyme activity. Finally, we report the location and the structure of the gene in the L. saxatilis genome and the presence of two additional non-functional gene copies. Altogether, we provide a missing link between the classical allozyme studies and the genome scans and bring together the results produced over decades of the genetic research.

Description: Climate change is causing fish stocks to shift, upending the social-ecological systems that rely on the historic distributions of these stocks and creating or exacerbating fisheries conflicts. The movements of internationally shared stocks between Exclusive Economic Zones (EEZs) or between EEZs and the high seas are especially concerning because they bring into play a variety of geopolitical factors and equity issues surrounding missing or conflicting regulations of jurisdictional boundary zones. Though many studies have explored the responses to and repercussions of shifting stocks on fisheries management, there is a dearth of interdisciplinary case studies that provide insight into the complexity of conflict formation in shifting transboundary fisheries, and that highlight the initial response stages where inclusion of proactive and cooperative measures can greatly improve a system's resilience to conflict. Our study helps to fill this gap by drawing on the knowledge of a diverse group of experts to analyze four case studies where transboundary stock shifts, geopolitical or governance tensions, and uncertainty regarding the future of the marine environment collide. Through synthesis of case study findings, we create a causal model of fishery conflict, within which we highlight factors that may heighten or mitigate the risk of conflict over shifting resources such as complex histories of power imbalance, unequal access to resources, or a lack of consistent and transparent data collection. Cooperation and equitable decision-making processes are recognized as vital components of internationally shared stock management which can promote lasting, effective, and conflict-resilient fisheries.

Description: Highlights: • Using a vHPO is efficient in increasing chemical diversity of natural extracts. • vHPO are a sustainable strategy to catalyze unspecific halogenation. • Metabolomics and bioinformatics are effective tools to highlight relevant molecules. • 12-bromo-communesin A is a novel brominated molecule with antimicrobial activity. This study reports for the first time the use of a vanadium chloroperoxidase (vCPO) enzyme to increase the chemical diversity of marine fungal extracts to generate new natural chemical entities. The vCPO used is a recombinant protein from the marine fungus Hortaea werneckii (HwvCPO). It catalyzes the formation of hypohalous acid (HOX), a highly reactive compound that can react with electron-rich substrates. Here, four fungal extracts obtained from different marine fungal strains (Penicillium expansum, Aspergillus pseudoglaucus, Trichoderma sp. and Hortaea werneckii) were investigated for enhancement of their chemical diversity. The metabolomic study showed that the enzymatic treatment of extracts of P. expansum and A. pseudoglaucus significantly boosted the chemodiversity by increasing the number of halogenated molecules. Indeed, respectively 5.07 and 6.65 times more halogenated ions were detected in ESI-MS profile of the extracts compared to negative controls. The new chemistry generated allowed the identification of new brominated compounds, one of which was further purified and characterized as 12-bromo-communesin A (2). This new compound, in contrast to communesin A (1), exhibited moderate antimicrobial activity on the methillicin-resistant Staphylococcus aureus (IC50 of 62 μM). This study has clearly demonstrated the employment of the vCPO enzyme to be a promising and environmentally friendly strategy to enhance the chemical diversity of natural extracts.

Description: Highlights: • We present a T5 record of the Pb isotope composition Labrador Sea seawater. • These data can be used to track Laurentide Ice Sheet (LIS) extent over Hudson Bay. • LIS retreat during T5 occurred over longer timescales than that for T2 and T1. • LIS deglaciation played important role in protracted nature of T5 sea-level rise. • Ice retreat during T1 may not be applicable template for older terminations in GIA modelling. Termination (T) 5, ∼424 ka, involved the biggest deglaciation of land-ice mass during the Quaternary. Warming and ice-sheet retreat during T5 led to an exceptionally long period of interglacial warmth known as Marine Isotope Stage (MIS) 11, ∼424–395 ka. A detailed understanding of the history of continental ice-sheet decay during T5 is required to disentangle regional contributions of ice-sheet retreat to sea-level rise (that range between ∼1 and 13 m above present day) and to correct it for glacio-isostatic adjustments (GIA). Yet little is known about the timing and magnitude of retreat during this time of the volumetrically most important continental ice sheet in the Northern Hemisphere, the Laurentide Ice Sheet (LIS). Here we present new authigenic Fe-Mn oxyhydroxide-derived high-resolution records of Pb isotope data and associated rare earth element profiles for samples spanning T5 from Labrador Sea IODP Site U1302/3. These records feature astronomically-paced radiogenic Pb isotope excursions that track increases in chemical weathering of North American bedrock and freshwater routing to the Labrador Sea via Hudson Straits associated with LIS retreat. Our records show that LIS retreat during T5 began 429. 2 ± 7.9 ka (2σ) and likely occurred over a longer timescale (by ∼10 to 5 kyr) than that observed for T2 and T1. They also show that Hudson Bay Ice Saddle collapse (and therefore LIS break-up) occurred ∼419 ± 4.7 ka (2σ), around the same time as best estimates of southern Greenland deglaciation, but ∼12 kyr before LIS deglaciation and the sea-level high-stand associated with the latter half of MIS 11 likely occurred. Our findings therefore highlight that ice-mass loss on North America likely played an important role in the seemingly protracted nature of T5 sea-level rise. A comparison of the deglaciation histories of the LIS and the southern Greenland Ice Sheet during T5, T2 and T1 also demonstrates that the well-constrained history of regional ice-sheet retreat during T1 is not always applicable as a template for older late Pleistocene terminations in GIA modelling.

Description: Carbon dioxide removal (CDR) technologies at a gigaton scale need to be developed and implemented within the next decades to keep global warming below 1.5 °C. Coastal enhanced silicate weathering is one of the proposed CDR techniques that aims to accelerate the natural process of CO2-sequestration during marine chemical weathering of silicate minerals. To this end, finely ground rock containing olivine (MgxFe2− xSiO4) could be dispersed in dynamic coastal environments, where local biotic and abiotic factors potentially enhance the weathering process. However, accurate predictions of the olivine dissolution rate and the associated CO2 sequestration under in situ conditions are currently lacking and ecosystem impacts remain to be assessed. Previously, it has been hypothesized that in situ grain collisions, induced by bed load transport due to currents and waves, could accelerate the in situ chemical weathering of olivine particles. To examine this, we investigated the effects of continuous grain tumbling on olivine dissolution in natural seawater. A 70-day experiment was conducted in which forsterite olivine sand was continuously tumbled in filtered seawater at different rotation speeds, and dissolution rates were measured on a weekly basis. Results showed that continuously tumbled olivine dissolved 8 to 19 times faster compared to stagnant (no rotation) conditions. Olivine dissolution was complete and stoichiometric (except for Ni release), air-seawater CO2 exchange was not significantly rate limiting, and minimal particle fragmentation and secondary mineral formation were observed. Hence, we infer that olivine weathering was mainly enhanced via advective pore water flushing, which limits saturation effects at the grain scale. Overall, this study provides evidence that ambient physical stresses in coastal environments could enhance marine silicate weathering, which has implications for both the natural silicon cycle as well as the use of enhanced coastal weathering of silicates as a CDR technique.

Description: Highlights • Study of wetland sediment in the easternmost Asian monsoon affected region. • Sediment on the Konsen Plateau has continuously deposited since ∼4.0 ka. • C/N and C/S ratios suggest environmental changes during the late Holocene. Abstract Wetland soils are among the largest carbon reservoirs in terrestrial ecosystems and are vulnerable to climate change. Here we elucidate the developmental history of a wetland soil located on the Konsen Plateau in Hokkaido, Japan, during the Holocene. Through radiocarbon dating of sediment samples, we revealed that continuous sedimentation persisted over the past 4000 years. This onset of peat sedimentation was simultaneous with those reported in other wetlands in eastern Hokkaido. We hypothesized that cooling associated with the end of climatic optimal may have contributed to peat preservation. Elemental analyses also confirmed the formation of a stable wetland condition during the late Holocene. The C/N ratios were approximately 15–25 throughout the core, indicating that the organic materials in the sediments were steadily derived from terrestrial plants. The C/S ratios of the core varied between 43 and 97, suggesting that the sediments are free from marine influences. Our results provided continuous and stable record of wetland sedimentary environment in eastern Hokkaido over the past 4000 years.

Description: The Ca isotope composition of calcite and aragonite can provide insights into their formation conditions. The accurate interpretation of the Ca isotope composition of natural samples, however, requires precise knowledge of the equilibrium Ca isotope fractionation between the solid and fluid phases. In this study, the three-isotope method with 42Ca, 43Ca and 44Ca has been used to estimate the equilibrium isotope fractionation of Ca between the CaCO3 minerals calcite and aragonite and the Ca2+ aquo ion. Reactive fluids were enriched with 43Ca and equilibrated with synthetic calcite and aragonite of natural Ca isotope distribution up to 3745 h at 25 °C. The isotopic composition of solids and fluids was measured using MC-ICP-MS and the estimated equilibrium fractionation for calcite-Ca2+(aq) and aragonite-Ca2+(aq) was Δ44/42Casolid-fluid=−0.02±0.13‰ and −0.80±0.10‰, respectively. Textural observations of the reacted solids suggest that isotope equilibration in aragonite experiments occurs via extensive Ostwald ripening, yielding large crystalline needles at the end of the experiments. In contrast, calcite did not exhibit an observable increase in size during the course of the experiments. Isotope exchange rates in the case of calcite are similar to those reported in previous studies and ∼4 orders of magnitude lower than the far-from-equilibrium calcite dissolution rate. Calcium isotope exchange rates for aragonite are more rapid than calcite driven by a greater extent of Ostwald ripening occurring via dissolution/precipitation reactions. The results of this study suggest that the Ca isotope compositions of calcite and aragonite crystals in chemical equilibrium, but isotope disequilibrium, with natural fluids could be significantly altered without overt evidence of diagenesis, especially in the case of calcite. The extent to which Ca isotope compositions are altered, however, would depend strongly on the environmental conditions, such as fluid:solid ratio and permeability of the solid facilitating fluid transport.

Description: Highlights: • First eddy–mean flow interaction analysis in the Deep Western Boundary Current between 5°S and 16°S. • Eddy kinetic energy is mainly generated via barotropic instability. • Enhanced upstream mean flow induces intensification in the downstream eddy field. Abstract: Thirty-six years output of a 1/10° eddy-resolving Ocean General Circulation Model are used to analyze the energetics of eddy–mean flow interactions in the Deep Western Boundary Current (DWBC) region of the tropical South Atlantic between 5°S and 16°S. The DWBC flow has a coherent structure between 5°S and 8°S but breaks up into a train of eddies downstream of a region of strong bathymetric curvature at 8°S. In the train of eddies area, the seasonal cycle of eddy kinetic energy (EKE) exhibits poleward phase propagation from May to September. The connection between the seasonal cycle of mean kinetic energy and EKE indicates an intensification of the downstream eddy field associated with enhanced upstream mean flow. The magnitudes of the baroclinic conversion and vertical eddy density flux terms are small in the DWBC core layer depth but somewhat elevated 500 m above and below the core. Eddy processes, including eddy generation and propagation, are accompanied by high EKE and large barotropic conversion. While in the global ocean baroclinic conversion is thought to dominate the energy transfer to EKE, our results suggest that barotropic energy conversion is the primary source of EKE and modulates its variability in the DWBC region of the deeper ocean.

Description: Anacardium humile (bushy cashew) is a native Brazilian plant with substantial pharmacological potential and noteworthy commercial significance in the food industry. This study introduces an untargeted metabolomics approach based on mass spectrometry for the comprehensive structural annotation of bioactive metabolites. The fruits were collected from three distinct sites and subjected to LC-HRMS/MS analysis. A total of eighty-eight compounds were putatively annotated across various metabolite classes. This unveiled a metabolic pro-file characterized by notable concentrations of polyphenols, including flavonoids, tannins, phenolic acids, and quinones, while aliphatic acids and terpenes were found in limited quantities. Noteworthy, no significant disparities in the metabolic content were observed among the collection sites. The three principal metabolites (peonidin 3-O-glucopyranoside, methylcyanidin and methyldelphinidin) underwent assessment for antioxidant activity via molecular docking analysis, subsequently generating structure-based feature pharmaco-phores. The process of annotation propagation yielded a comprehensive qualitative appraisal of the A. humile metabolome. The outcomes obtained offer potential candidates for further exploration of their nutraceutical attributes.(c) 2023 Published by Elsevier B.V. on behalf of SAAB.

Description: Total alkalinity (TA) is a variable that reflects the acid buffering capacity of seawater, and is key to studies of the global carbon cycle. Daily and seasonal TA variations are poorly constrained due to limitations in observational techniques, and this hampers our understanding of the carbonate system. High quality and high temporal resolution TA observations are required to constrain the controlling factors on TA. Estuarine and coastal waters usually have low TA values and may experience enhanced remineralization of organic matter in response to processes such as eutrophication and terrestrial organic matter input. Therefore, these waters are considered vulnerable to acidification as a consequence of ongoing atmospheric anthropogenic carbon dioxide uptake. An In Situ Analyzer for seawater Total Alkalinity (ISA-TA) was deployed for the first time in low salinity, dynamic estuarine waters (Kiel Fjord, southwestern Baltic Sea). The ISA-TA and a range of additional sensors (for pH, pCO2, nitrate and temperature, salinity, dissolved oxygen) used to obtain ancillary data to interpret the TA variability, were deployed on a pontoon in the inner Kiel Fjord for approximately four months. Discrete samples (for TA, nutrients including NO3−, soluble reactive phosphorus (SRP) and H4SiO4, chlorophyll a) were collected regularly to validate the ISA-TA and to interpret the TA data. The effects on TA in the study area of nitrate uptake and of other processes such as precipitation, run-off and mixing of different waters were observed. The difference between the TA values measured with the ISA-TA and TA of discretely collected samples measured with the Gran titration method was −2.6 ± 0.9 μmol kg−1 (n = 106), demonstrating that the ISA-TA provides stable and accurate TA measurements in dynamic, low salinity (13.2–20.8), estuarine waters. The TA and ancillary data recorded by the sensor suite revealed that physical mixing was the main factor determining the variability in TA in Kiel Fjord during the study period.

Description: This study investigates the historical characteristics and future trends of marine heatwaves (MHWs) in the Western North Pacific (WNP) region. During the historical period from 1982 to 2014, the WNP region experiences an average MHW frequency of 0.89 ± 0.18 count/year. These events have an average duration of 8.64 ± 1.39 days/count. Annually, the cumulative MHW days amount to 7.76 ± 2.23 days, with an accumulated intensity of 15.73 ± 6.43 °C days. The maximum intensity recorded during this period reaches 2.04 ± 0.54 °C, while the average intensity stands at 1.74 ± 0.48 °C/count. In the evaluation of 14 CMIP6 models, five optimal models, namely GFDL-ESM4, EC-Earth3-Veg, EC-Earth3, BCC-CSM2-MR, and MRI-ESM2-0, are selected for simulating future MHWs. Based on the simulation results of these five models under the SSP2-4.5 and SSP5-8.5 scenarios for the future period (2015–2100), it is found that under the SSP2-4.5, the frequency of MHWs is slightly higher compared to the SSP5-8.5. However, under the SSP5-8.5, MHWs exhibit higher accumulated intensity, maximum intensity, and average intensity, with a predominance of high-intensity MHWs in the Kuroshio Extension region. The occurrence area ratio in the future is significantly larger than in the historical period. Moreover, MHWs intensity displays a seasonal variation, with stronger during summer and weaker during winter. This study provides important insights into MHWs in the WNP region, offering valuable information for decision-makers in formulating response measures and reducing economic losses.

Description: The Cretaceous Twihinate carbonatite in the Moroccan Sahara is a ~ 5 km diameter ring-shaped intrusion made of an inner core preserving sparse occurrences of medium- to coarse-grained calcite carbonatite encircled by a ring of vuggy siliceous breccia. The Twihinate carbonatite is enriched in large ion lithophile elements (Cs, Rb, Ba, U and Th) and light rare earth elements (LREE), but shows negative anomalies in high field strength elements (particularly Ta, Zr, Hf and Ti). Stable and radiogenic isotope ratios vary in the range of δ13Cv-PDB = −10.5 to −1.6‰, δ18OV-SMOW = 6.4–28.3‰, initial 87Sr/86Sr = 0.7034–0.7043 (εSri between −14.5 and − 1.8), 143Nd/144Nd = 0.51282–0.51283 (εNdi between 2.8 and 3.6), 206Pb/204Pbi = 19.52–23.78, 207Pb/204Pbi = 15.56–15.69 and 208Pb/204Pbi = 38.69–39.02). Altogether, these isotopic compositions reflect compositional mantle heterogeneity, and are interpreted to reflect partial melting of heterogenous mantle sources with a potential eclogite component in an intraplate, rift-controlled tectonic setting. From a geodynamic perspective, the time span ascribed to age emplacement of Twihinate carbonatite shortly follows the Upper Jurassic hyper-extension event which ultimately resulted in mantle exhumation and subsequent onset of drifting in the Central Atlantic Ocean and Maghrebian Tethys.