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  • 1
    Publication Date: 2020-10-23
    Description: The Mikabu Unit (Mikabu greenstones) was an oceanic plateau that was in the Mesozoic Paleo-Pacific Ocean. Large-igneous-province (LIP) activity has been proposed as the origin of the oceanic plateau of the Mikabu Unit. This study aims to reveal LIP activity in the Paleo-Pacific Ocean. We present geochemical and geochronological data for the Mikabu Unit and the Middle Jurassic to Early Cretaceous Chichibu accretionary complex (i.e., the Kashiwagi and Kamiyoshida units), both of which underwent the same high-pressure low-temperature metamorphism as the Mikabu Unit, in the Kanto Mountains, central Japan. The Mikabu Unit contains oceanic plateau basalts characterized by incompatible element depletion and high chondrite normalized Gd/Yb ratios. These basalts are interpreted to have erupted in the age of 157.0 ± 0.9 Ma (Late Jurassic), based on zircon U–Pb dating of anorthosite. The basalt geochemistry indicates that oceanic plateau basalts occur in the Kashiwagi Unit. Although basalts in the Mikabu Unit were thought to have formed at the Pacific–Izanagi–Farallon triple junction in the previous studies, we propose they formed on older oceanic crust of the Izanagi Plate during the Late Jurassic, which was located several thousand kilometers from the triple junction. The Kashiwagi and Mikabu units were accreted to Asia during the Early Cretaceous.
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  • 2
    Publication Date: 2020-11-05
    Description: Constraining the behaviour of Re and Os during eclogite melting is required to understand the Re and Os budget and 187Os/188Os of recycled slabs produced at warm subduction zones. It is particularly relevant to early Earth history, a period during which slab melting could have prevailed over dehydration due to higher mantle temperatures. There are however currently few constraints on Re and Os mobility during slab melting. Accordingly, we measured Os, Re and 187Os/188Os in primitive submarine lavas (Mg# ˃ 0.6) from the western Aleutian Arc. These include strongly adakitic rocks shown to be derived from eclogite melting (high-Mg# andesite, dacites and rhyodacites), as well as non-adakitic rocks (high-Mg# andesites, basaltic andesites and basalts) with variable sediment and fluid-derived slab contributions for comparison. The 187Os/188Os of the adakitic and non-adakitic volcanic rocks vary significantly but largely overlap. In both groups, the most radiogenic values occur in samples with the lowest Os concentrations, thus implicating crustal assimilation as the main cause of Os isotope variations. Adakitic and non-adakitic rocks least affected by crustal assimilation have overlapping 187Os/188Os of 0.141–0.149. We show that the source of the adakites is very unlikely to comprise significant eclogite-derived Os, which suggests no or minimal mobilization of Os during eclogite melting. Eclogitic Os is inferred to be retained in sulphides or replacement phases formed upon sulphide breakdown for which Os has high affinity, such as a platinum-group minerals (PGMs). The small Os budget of the adakites is most likely derived from limited reaction with the mantle wedge during ascent. Degassing has reduced Re contents in most samples, but not for end-member adakites (SiO2 〉 67% and Sr/Y 〉 200; n = 4) that were erupted at seafloor depths 〉 2500 m. These undegassed samples have elevated Re concentrations (0.8–1.5 ppb) that are positively correlated with Sr/Y and so are interpreted to be primary magmatic concentrations resulting from the mobilization of Re from the slab. Re could either be derived from the eclogites or from the serpentinite-derived fluids fluxing eclogites during melting. The former scenario would produce recycled residual crusts with lower Re/Os than in unmelted eclogites while the latter would result in Re/Os ranging from similar to higher than prior to melting. In both cases, the Re/Os and therefore the time-integrated 187Os/188Os of residual crust produced at warm subduction zones involving slab melting are likely to be different from that processed at cooler typical modern subduction zones. Therefore, if slab melting was an important process during the early Earth, the use of Re and Os partitioning in modern subduction zones to model the source of magmas comprising old recycled oceanic crust, such as the HIMU (high μ = 238U/204Pb) ocean island basalts (OIBs), might lead to erroneous interpretations.
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  • 3
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    ASCE (American Society of Civil Engineers)
    In:  Journal of Geotechnical and Geoenvironmental Engineering, 147 (1). Art.Nr. 04020148.
    Publication Date: 2020-11-25
    Description: Methane hydrate within a soil pore space may significantly modify the mechanical behavior of the sediment. Previous studies have shown that the influence of hydrate on methane-hydrate-bearing sediments (MHBS) is dilative through pore-scale kinematic constraining, which in turn affects mechanical properties such as strength and stiffness. This paper presents a new analytical–empirical approach for evaluating kinematic aspects of MHBS. The suggested approach incorporates explicit experimental kinematics data of the host soil together with an analytical amplification factor. Based on known stress-dilatancy expressions, this analytical factor is found with a strong relation to stress ratios of MHBS to host soil during mechanical testing. A stress ratio model is suggested, which is developed based on a thorough study of various stress ratios from test results of both artificial and natural methane-hydrate-bearing sediments from different works. Using the suggested approach, mechanical models may consist of fewer model parameters, which may increase the model efficiency and yield a deeper understanding of fundamental mechanical characteristics of MHBS.
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  • 4
    Publication Date: 2020-11-25
    Description: Highlights: • NW Pacific ice-rafted debris found further south than previously thought. • Largest iceberg events were comparable in magnitude to N Atlantic Heinrich Events. • Iceberg flux to ODP Site 1207 was episodic throughout the late Quaternary. • Kamchatka-Koryak bergs frequently reached south of the N Pacific Subarctic Front. • Ice-rafting and climate contrast sharply between the last two glacial periods. Abstract: The ice-rafted-debris (IRD) record of the open Northwest Pacific points towards the existence of substantial glacial ice on the Northeast Siberian coast during the late Quaternary. However, the scale and timing of glaciation and de-glaciation remains controversial due to the dearth of both onshore and offshore records. Existing IRD data suggests at least one event of dynamic and abrupt change during mid-late Marine Isotope Stage (MIS 3) which mimics the massive collapse of the Laurentide ice sheet during Heinrich Events. It is uncertain whether other events of this magnitude occurred during the late Quaternary. Here we present a ∼160,000 yr IRD series, planktic foraminiferal counts and an age model, derived from a benthic O curve, radiocarbon dates and tephrochronology, from core ODP 1207A (37.79°N, 162.75°E), revealing the presence of low but episodic flux of IRD. We conclude that glacial Northwest Pacific icebergs spread further south than previously thought, with icebergs emanating from Northeast Siberia being transported to the transition region between the subpolar and subtropical waters, south of the subarctic front during at least the Quaternary's last two glacial periods. The episodic nature of the 1207A IRD record during the last glacial, combined with coupled climate-iceberg modelling, suggests occasional times of much enhanced ice flux from the Kamchatka-Koryak coast, with other potential sources on the Sea of Okhotsk coast. These findings support the hypothesis of a variable but extensive ice mass during the last glacial over Northeast Siberia, particularly early in the last glacial period, behaving independently of North American and Eurasian ice masses. In strong contrast, IRD was absent during much of the penultimate glacial Marine Isotope Stage (MIS) 6 suggesting the possibility of very different Northeast Siberian ice coverage between the last two glacial periods.
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  • 5
    Publication Date: 2020-12-11
    Description: The Kerguelen Islands are part of the French Southern Territories, located at the limit of the Indian and Southern oceans. They are highly impacted by climate change, and coastal marine areas are particularly at risk. Assessing the responses of species and populations to environmental change is challenging in such areas for which ecological modelling can constitute a helpful approach. In the present work, a DEB-IBM model (Dynamic Energy Budget – Individual-Based Model) was generated to simulate and predict population dynamics in an endemic and common benthic species of shallow marine habitats of the Kerguelen Islands, the sea urchin Abatus cordatus. The model relies on a dynamic energy budget model (DEB) developed at the individual level. Upscaled to an individual-based population model (IBM), it then enables to model population dynamics through time as a result of individual physiological responses to environmental variations. The model was successfully built for a reference site to simulate the response of populations to variations in food resources and temperature. Then, it was implemented to model population dynamics at other sites and for the different IPCC climate change scenarios RCP 2.6 and 8.5. Under present-day conditions, models predict a more determinant effect of food resources on population densities, and on juvenile densities in particular, relative to temperature. In contrast, simulations predict a sharp decline in population densities under conditions of IPCC scenarios RCP 2.6 and RCP 8.5 with a determinant effect of water warming leading to the extinction of most vulnerable populations after a 30-year simulation time due to high mortality levels associated with peaks of high temperatures. Such a dynamic model is here applied for the first time to a Southern Ocean benthic and brooding species and offers interesting prospects for Antarctic and sub-Antarctic biodiversity research. It could constitute a useful tool to support conservation studies in these remote regions where access and bio-monitoring represent challenging issues.
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  • 6
    Publication Date: 2020-12-14
    Description: The facies distribution in time and space of sedimentary successions is controlled by a complex interplay between physical, chemical and biological processes, which are nowadays difficult to construe from the geological record. Numerical models constitute a valuable tool to identify and quantify such controlling factors permitting a reliable 3D extrapolation and prediction of stratigraphic and facies architectures beyond outcropping rock strata. This study assesses the roles of three controlling parameters being carbonate production rate, relative sea-level changes and terrigenous clastic sediment supply, on the evolution of an Aptian carbonate system. The SIMSAFADIM-CLASTIC, a 3D process-based sedimentary-stratigraphic forward model, was used for this evaluation. The carbonate succession modelled crops out in the western Maestrat Basin (E Iberia), and corresponded to a platform-to-basin transition comprising three depositional environment-related facies assemblages: platform top, slope and basin. Testing of geological parameters in forward modelling results in a wide range of possible 3D geological scenarios. The documented distribution of facies and sequence-stratigraphic framework combined with a virtual outcrop model were used as a reference to perform geometric (quantitative) and architectural and stacking pattern (qualitative) research by model-data comparison. The time interval modelled spans 1450 ky. The best-fit simulation run characterizes and quantifies (1) relative sea-level fluctuations recording five different genetic types of deposit (systems tracts) belonging to two depositional sequences as expected from field-data analysis, (2) a rate of terrigenous clastic sediment input ranging between 0.5 and 2.5 gr/s, and (3) a mean autochthonous carbonate production maximum rate of 0.08 m/ky. Furthermore, the quantitative and qualitative sensitivity tests carried out highlight that the fluctuation of relative sea level exerted the main control on the resulting stratigraphic and facies architectures, whereas the effect of inflowing terrigenous clastic sediment is less pronounced. Facies assemblages show different sensitivities to each parameter, being the slope carbonates more sensitive than the platform top facies to inflowing fine terrigenous sediments. On slope depositional settings, siliciclastic input also controls stratal stacking patterns and the dimensions of the carbonate bodies formed. The final 3D model allows to spot architectural features such as stacking patterns that can be misinterpreted by looking at the resulting record in the outcrop or by using other 2D approaches, and facilitates the comprehension of reservoir connectivity highlighting the occurrence of initial disconnected regressive platforms, which were later connected during a transgressive stage.
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  • 7
    Publication Date: 2021-01-06
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  • 8
    Publication Date: 2021-01-06
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  • 9
    Publication Date: 2021-01-07
    Description: Highlights • The workflow to minimise uncertainties in thermal modelling of the basin is presented. • Different methods of basin thermal history reconstruction are compared. • Accounting of the blanketing effect in West Siberian Basin is important. Abstract Knowledge of the thermal history of a sedimentary basin is necessary for the quantitative and qualitative estimation of hydrocarbons generated from buried organic matter. Usually, specialists use a combination of backstripping and forward temperature modelling techniques for a basin history reconstruction. However, this approach decouples the structural and thermal solutions and therefore results in the less consistent modelling. The reliability of a basin model can be increased by using coupled approaches that resolve the structural and thermal solutions simultaneously. In this work, we investigate how using a backstripping-based versus a coupled thermo-tectono-stratigraphic approach for computing basement heat flow influences the predicted total hydrocarbon generation using a 808 km transect across the West Siberian basin as an example. Both coupled and decoupled approaches are used to reconstruct a basal heat flow history for the transect. Corresponding models have identical geological parameters and are calibrated with a set of temperature and vitrinite reflectance data. Furthermore, reconstructed heat flow histories are used separately as a lower boundary condition in a petroleum system model to evaluate the consequences for hydrocarbon generation. We find that the backstripping-based approach significantly overestimates hydrocarbon generation mass with respect to the basement heat flow solution obtained from the more consistent thermo-tectono-stratigraphic model. Also, the onset and time evolution of hydrocarbon generation is substantially different. These findings, obtained for the West Siberian Basin, show that calibrating a thermal model to the wellbore temperature and vitrinite data can lead to the inaccurate interpretation of the thermal history. The study results suggest that the presented advanced basin modelling strategy can help in decreasing risks in petroleum system analysis by providing more reliable and consistent heat flow solutions.
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  • 10
    Publication Date: 2021-01-07
    Description: Filter-feeding zooplankton in lakes feed on a mixture of phytoplankton, bacteria, and terrestrial particles and the proportions and nutritional value of these components can be highly variable. However, the extent to which food quality interacts with food quantity in affecting overall zooplankton performance is not yet fully resolved. Here we performed laboratory feeding experiments to test how the performance of the unselective filter feeder Daphnia galeata was affected if various quantities of high-quality food (the phytoplankton Rhodomonas) were diluted with low-quality food such as heterotrophic bacteria (Pseudomonas) or terrestrial detritus particles (t-POM) from the riparian zone of a boreal forest stream. We hypothesised: that increased proportions of bacteria and t-POM in the diet will lead to decreased survival, somatic growth; and reproduction of Daphnia despite the presence of phytoplankton; that these effects are more pronounced for t-POM than for heterotrophic bacteria; and that this response is stronger when phytoplankton availability is low. Increasing the concentrations of Pseudomonas affected Daphnia survival, growth, and reproduction negatively when Rhodomonas was available at intermediate (0.37 mgC/L) and high (0.55 mgC/L) quantities. When Rhodomonas quantity was low (0.22 mgC/L), the addition of Pseudomonas generally resulted in better Daphnia performance except at very high concentrations of the bacterium relative to Rhodomonas. In contrast, the addition of t-POM was detrimental for overall Daphnia performance at all Rhodomonas concentrations. Daphnia performance was best described by a model including the interaction between food quality and quantity, with stronger negative effects on Daphnia when high-quality food was supplemented with t-POM than with Pseudomonas. The results indicate that the ability of zooplankton to use low-quality food is affected by the concurrent availability of high-quality food. Furthermore, food sources that can be used but do not fulfil dietary requirements of grazers (e.g. bacteria), may still provide nutritional benefits as long as other complementary food components are available in sufficient quantities to compensate for biochemical deficiencies. Therefore, we conclude that heterotrophic bacteria, but not peat layer t-POM, can be an important component of zooplankton diets in boreal lakes, especially if the concentration of phytoplankton is low.
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  • 11
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    Springer
    In:  Hydrobiologia, 848 . pp. 143-155.
    Publication Date: 2021-01-13
    Description: We review the literature on the relationship between water temperature and size of freshwater phytoplankton, to examine the hypothesis that freshwater phytoplankton, like marine phytoplankton and many other groups of organisms, conform to Bergmann's Rule and become smaller with warming. We provide both experimental and field evidence in support of the above hypothesis, much of this evidence was hidden in studies focused on other issues, but presenting temperature and phytoplankton size data. Freshwater phytoplankton size shrinks with increasing temperature at both the species level (by cells or colonies becoming smaller) and at the community level (shift to smaller species). Exceptions to the Rule do occur but in most cases those exceptions can be explained by indirect effects of temperature on phytoplankton size, via processes such as grazing or nutrient availability. With global warming, freshwater phytoplankton are likely to be of smaller size. This article is dedicated to Colin S. Reynolds, who has had a leading role in our personal education and understanding of phytoplankton ecology.
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  • 12
    Publication Date: 2021-01-13
    Description: Global anthropogenic mercury (Hg) emissions to the atmosphere since industrialization are widely considered to be responsible for a significant increase in surface ocean Hg concentrations. Still unclear is how those inputs are converted into toxic methylmercury (MeHg) then transferred and biomagnified in oceanic food webs. We used a unique long-term and continuous dataset to explore the temporal Hg trend and variability of three tropical tuna species (yellowfin, bigeye, and skipjack) from the southwestern Pacific Ocean between 2001 and 2018 (n = 590). Temporal trends of muscle nitrogen (δ15N) and carbon (δ13C) stable isotope ratios, amino acid (AA) δ15N values and oceanographic variables were also investigated to examine the potential influence of trophic, biogeochemical and physical processes on the temporal variability of tuna Hg concentrations. For the three species, we detected significant inter-annual variability but no significant long-term trend for Hg concentrations. Inter-annual variability was related to the variability in tuna sampled lengths among years and to tuna muscle δ15N and δ13C values. Complementary AA- and model-estimated phytoplankton δ15N values suggested the influence of baseline processes with enhanced tuna Hg concentrations observed when dinitrogen fixers prevail, possibly fuelling baseline Hg methylation and/or MeHg bioavailability at the base of the food web. Our results show that MeHg trends in top predators do not necessary capture the increasing Hg concentrations in surface waters suspected at the global oceanic scale due to the complex and variable processes governing Hg deposition, methylation, bioavailability and biomagnification. This illustrates the need for long-term standardized monitoring programs of marine biota worldwide.
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  • 13
    Publication Date: 2021-01-13
    Description: Highlights • A cascade biorefinery process for Sargassum muticum (Sm) was proposed. • Dried sap (2% of raw material) was enriched in K and stimulated stem and root growth. • Similar alginate, phenolics and fucoidan yields and properties to those from unpressed Sm. • Methane production from autohydrolysis solids increased by 55-76% compared to the use of Sm. • The autohydrolysis at a maximum of 150 °C was optimal for different products. Abstract Marine macroalgae represent an excellent material to be used as biogas producer, adsorbent, biostimulant and fertilizer for soils, or feedstock. The success in the exploitation of seaweeds depends on their characteristics, and the approach used to separate their specific active components. In the context of circular economy, invasive species are a good candidate for exploitation, and biorefinery a key valorization technique. Here we investigate a novel biorefinery scheme for a fuller valorization of the alien species Sargassum muticum. An initial pressing stage allowed the production of a Sap fraction, which showed potential as a plant biostimulant, increasing both root development and shoot/root ratio, especially when used at a dose of 0.1 g/L lyophilized Sap. The solids after pressing were processed by non isothermal autohydrolysis, using pressurized hot water under subcritical conditions (120-210 °C), previously optimized to solubilize the fucoidan and phlorotannin fractions. The residual solids remaining after pressing and autohydrolysis stages were evaluated for the production of biogas. The obtained value (150 mL CH4/g residual solids at 150 °C) is significantly higher than that found for the raw seaweed. The optimal autohydrolysis temperature (150 °C) is compatible with the production of the fucoidan fraction, although the phenolic content is favoured at stronger operation conditions. We also discuss the possibility of preparing adsorbents for pollutant removal and mineral amendments from the autohydrolysis waste solids.
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  • 14
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    Society for Chaos Theory in Psychology and Life Sciences
    In:  Nonlinear dynamics, psychology, and life sciences, 25 (1). pp. 113-123.
    Publication Date: 2021-01-13
    Description: Artistic technique and scientific discovery are superficially contradictory, but are unified at their core as products of creativity. I have always embraced both disciplines, but at some point during my academic journey, I lost my imagination and ability to dream creatively. For over a decade, I have remained passionate about perfecting a way to retrieve this intrinsic component of myself, and nurture it in my students and peers. We must think anew and act anew - bridge the gulf between the disciplines of art and science - if we are to rescue creativity in scientific discovery, and retain many of the bright minds that burn out and even leave academia in science. Surrealism and fractals in nature are such bridges, and offer a space for early career scientists to embrace the full breadth and cultural capacity of science. Here, I present a retrospective review of artworks I have produced over nearly two decades, in considering how they reflect my mindset and relationship with science at various stages of my academic journey.
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  • 15
    Publication Date: 2021-01-13
    Description: Local carbonate cycling in lagoon-estuarine systems, involving processes such as inorganic and biogenic carbonate precipitation/dissolution, represents an important but poorly constrained component of the coastal carbon budget. This study investigates the sensitivity of stable Sr isotope tracer (δ88/86Sr) with respect to carbonate saturation and salinity of local waters in the Coorong, Lower Lakes and Murray Mouth (CLLMM) estuary in South Australia. The CLLMM has an extensive range of salinity from fresh to hypersaline (from ∼0 to over 100 PSU), with corresponding variations in water chemistry and major ion composition that in turn controls mineral saturation states, and thus CaCO3 precipitation/dissolution in local waters. Here we use the novel δ88/86Sr tracer in tandem with the more established radiogenic Sr isotope ratio (87Sr/86Sr), where the latter is a robust proxy for Sr sources and thus water provenance. We also produced a geochemical (PHREEQC) model of calcium carbonate (CaCO3) saturation changes across this unique lagoon-estuarine system. The results indicate a systematically increasing trend of δ88/86Sr (from ∼0.25‰ to ∼0.45‰) with increasing salinity and CaCO3 (aragonite, calcite) saturation indices of the coastal waters, which in turn suggest an overall control of carbonate dissolution/precipitation processes on the stable Sr isotope composition in the CLLMM system. This was further corroborated by Ca isotope data (δ44/40Ca) published previously on the same samples from the Coorong, as well as a quantitative simulation of local carbonate removal in the lagoon based on Rayleigh modelling and Sr isotope data. Overall, our results confirm that a coupled Sr isotope approach (combining 87Sr/86Sr and δ88/86Sr) can be used to constrain not only the main water sources (continental versus marine Sr) but also local CaCO3 dissolution/precipitation processes, and thus inorganic carbon and coastal carbonate cycling in the CLLMM system. Finally, this coupled δ88/86Sr and 87Sr/86Sr approach can be potentially applied to fossil carbonate archives to reconstruct paleo-hydrology and salinity changes in the CLLMM and/or other carbonate-producing coastal systems.
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  • 16
    Publication Date: 2021-01-13
    Description: Highlights • Geochemical analyses highlight multiple diagenesis processes occurring in the sediment. • Intense methane seepages and organic matter degradation contribute to the sulfate reduction. • Chemical of dissolved and mineral iron species indicate that iron is associated with clay minerals. • In response to seawater intrusion, ion exchange, dissolution and reverse weathering reactions change the composition of clay constituting the sediment. Abstract Pore water and sediment geochemistry in the western Black Sea were investigated on long Calypso piston core samples. Using this type of coring device facilitates the recovery of the thick sediment record necessary to analyze transport-reaction processes in response to the postglacial sea-level rise and intrusion of Mediterranean salt water 9 ka ago, and thus, to better characterize key biogeochemical processes and process changes in response to the shift from lacustrine to marine bottom water composition. Complementary data indicate that organic matter degradation occurs in the upper 15 m of the sediment column. However, sulfate reduction coupled with Anaerobic Methane Oxidation (AOM) is the dominant electron-accepting process and characterized by a shallow Sulfate Methane Transition Zone (SMTZ). Net silica dissolution, total alkalinity (TA) maxima and carbonate peaks are found at shallow depths. Pore water profiles clearly show the uptake of K+, Mg2+ and Na + by, and release of Ca2+ and Sr2+ from the heterogeneous lacustrine sediments, which is likely controlled by chemical reactions of silicate minerals and changes in clay mineral composition. Iron (Fe2+) and manganese (Mn2+) maxima largely coincide with Ca2+ peaks and suggest a close link between Fe2+, Mn2+ and Ca2+ release. We hypothesize that the Fe2+ maxima below the SMTZ result from deep Fe3+ reduction linked to organic matter degradation, either driven by DOC escaping from the shallow sulfate reduction zone or slow degradation of recalcitrant POC. The chemical analysis of dissolved and solid iron species indicates that iron is essentially associated with clay minerals, which suggests that microbial iron reduction is influenced by clay mineral composition and bioavailability of clay mineral-bound Fe(III). Overall, our study suggests that postglacial seawater intrusion plays a major role in shaping redox zonation and geochemical profiles in the lacustrine sediments of the Late Quaternary.
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  • 17
    Publication Date: 2021-01-13
    Description: Highlights • India is industrializing rapidly with significant releases of Pb. • Increase in anthropogenic Pb input to Indian shelf occurred over last 40 years. • Sediment leachate Pb isotopes used to assess anthropogenic Pb inputs • Sources of Pb in eastern and western shelves of India were different. • Inland coal combustion and heavy industries are major sources of Pb. India is industrializing rapidly and with this there comes higher releases of contaminants into the environment. Change in Pb deposition over the last century on the eastern (off Andhra Pradesh) and western (off Karnataka) shelves of India was investigated based on the data extracted from two sediment cores covering the past ~114 and ~145 yrs. The variations of the total Pb content, its enrichment factor, and concentrations of non-residual Pb in both the sediment cores document that there was a gradual increase in anthropogenic Pb input into the coastal sediments of India over the last century. Sediment leachates were used to monitor the increase in anthropogenic Pb input and its Pb isotope composition. The anthropogenic end member composition of the western shelf sediment location (206Pb/207Pb: 1.105; 206Pb/208Pb: 2.149) was significantly less radiogenic than the eastern shelf isotopic composition (206Pb/207Pb: 1.145; 206Pb/208Pb:2.120). A binary mixing model suggests that Pb emitted from the heavy industries (e.g., ore mining, Pb processing and smelting plants) of India has been the major source of anthropogenic Pb to the sediments of western continental shelf. In contrast, the isotopic signatures suggest that coal combustion is responsible for elevated anthropogenic Pb levels in the sediments from the eastern shelf of India.
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  • 18
    Publication Date: 2021-01-13
    Description: Highlights: • The pivot point for sea level shifted to the west of the Nino4 region in the 2000s. • This enabled the thermocline feedback to increase strongly in the Central Pacific. • The resulting increase in CP events maintains the pivot point to the west, a positive feedback mechanism. Monthly mean sea level variations computed using a linear, reduced-gravity, multi-mode model are combined with satellite measurements to explore why Central Pacific (CP) ENSO events occur more frequently since 2000s. The pivot point for sea level (and hence thermocline) variations has shifted westward in response to an increase in zonal wind stress variance in the western equatorial Pacific. As a result, the Nino4 region is increasingly to the east of the pivot point enabling the thermocline feedback to operate there, strengthening the Bjerknes feedback mechanism in the Nino4 region and leading to an increase in the occurrence of CP events. The increased variance of wind stress in the western Pacific is, in turn, caused by the resulting increase in the frequency of CP events. These arguments imply a positive feedback in which CP events are self-maintaining and suggest that they may be part of the natural variability of the climate system and could occur without the need for changes in external forcing.
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  • 19
    Publication Date: 2021-01-13
    Description: Highlights • First dissolved Nd/Hf isotope and REE data from the Congo River Plume. • High REE and Hf fluxes from the Congo River to the southeast Atlantic. • Conservative river and surface seawater mixing of Nd/Hf isotopes and REEs/Hf at S 〉 23. • Congo River particles impact intermediate and deep water signals of NE Angola Basin. Abstract The Congo River is the second largest river by discharge in the world and a major source of element inputs into the South Atlantic Ocean. Yet, the element fluxes and transport mechanisms across and beyond its estuary and their impacts on the marine distribution and cycling of many major and trace elements are not well understood. We present the first combined dissolved neodymium (Nd) and hafnium (Hf) isotope and rare earth element (REE) concentration distributions following the Congo River plume along its flow path off the West African coast and along a connected offshore latitudinal section at 3°S. The Congo River freshwater itself is characterized by extraordinarily high Nd and Hf concentrations of up to 4000 pmol/kg and 54 pmol/kg, and by Nd (εNd) and Hf (εHf) isotope compositions that range between −15.6 and −16.4 and between 0.35 and −1.4, respectively. Our near- and offshore data indicate that at salinities above 23 conservative mixing of Congo-derived Nd and Hf concentrations and isotopic signatures with ambient surface seawater occurs for at least 1000 km to the northwest of the river mouth. This demonstrates a large spatial extent of the influence of the Congo plume on trace metal distributions in the eastern south Atlantic surface waters. A comparison between dissolved Nd and Hf fluxes from the Congo River and the shelf zone estimated based on radium isotope compositions indicate that release from Congo-derived particulate phases likely balances strong estuarine REE and Hf removal in the low salinity zone. The combined riverine and shelf zone flux for Nd is almost twice as high as that estimated for the Amazon River, despite that the Amazon discharge is about five times higher than that of the Congo River. Even the offshore Nd flux estimated for the 3 °S transect based on radium isotope compositions still corresponds to ∼40% of the Congo-shelf-zone flux and reaches 150 ± 50 Mg/year for Nd. Moreover, intermediate waters below the plume are strongly affected by exchange with particulate inputs from the Congo River given that Nd isotope signatures are inconsistent with values expected from large-scale water mass mixing and instead support unradiogenic Nd release either from sinking or deposited Congo-derived detrital material. Deep and bottom water isotopic signatures are also slightly affected by interaction with particles and benthic Nd release.
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  • 20
    Publication Date: 2021-01-13
    Description: Seagrass meadows are globally recognized as important coastal habitats due to the various ecological functions and ecosystem services they provide. Substantial global decline of seagrass habitats has been recorded over the last decades, underlining the need for extensive studies, including monitoring and mapping these habitats across their distributional range. Cymodocea nodosa (Ucria) Ascherson is the only seagrass species reported in the archipelago of Madeira (NE Atlantic) and systematic or reliable information of its occurrence is very scarce and mostly anecdotal. This study reports the discovery of a yearly-persistent patch of C. nodosa in the southeast coast of Madeira and provides insights into key ecological and biological aspects (e.g. density, leaf length, associated fauna and flora). Seasonal monitoring surveys over a 3-year period, indicate that (1) the patch has increased in size and shoot density over the study period, and (2) leaf lengths follow a typical seasonal pattern over the year. Accounts of past destruction of seagrass meadows in the island, underline the importance of continuous monitoring of the patch and adjacent areas to reveal how the current seagrass patch develops (i.e. patch continuity and/or disappearance), if it integrates a larger meadow and whether anthropogenic pressures as coastal development and/or associated terrigenous sediment runoff events will affect its resilience.
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  • 21
    Publication Date: 2021-01-13
    Description: Ocean acidification (OA) will affect marine biotas from the organism to the ecosystem level. Yet, the consequences for the biological carbon pump and thereby the oceanic sink for atmospheric CO2 are still unclear. Here we show that OA considerably alters the C/N ratio of organic-matter export (C/Nexport), a key factor determining efficiency of the biological pump. By synthesizing sediment-trap data from in situ mesocosm studies in different marine biomes, we find distinct but highly variable impacts of OA on C/Nexport, reaching up to a 20% increase/decrease under partial pressure of CO2 (pCO2) conditions projected for 2100. These changes are driven by pCO2 effects on a variety of plankton taxa and corresponding shifts in food-web structure. Notably, our findings suggest a pivotal role of heterotrophic processes in controlling the response of C/Nexport to OA, thus contradicting the paradigm of primary producers as the principal driver of biogeochemical responses to ocean change.
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  • 22
    Publication Date: 2021-01-13
    Type: Report , NonPeerReviewed
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  • 23
    Publication Date: 2021-01-13
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  • 24
    Publication Date: 2021-01-13
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  • 25
    Publication Date: 2021-01-13
    Description: In aquatic systems, invasive submerged macrophytes considerably alter the structure and functioning of communities, thus potentially compromising ecosystem services. The prolific spread of invasive macrophytes is often aided by vegetative fragment propagation, yet the contributions of various commonly occurring invertebrates to such fragmentation are often unquantified. In the present study, we examine fragmentary spread of invasive macrophytes by a group of shredder-herbivores, larval caddisflies. Through novel application of the comparative functional response (FR; resource use as a function of density) approach to the native case-building species Limnephilus lunatus, we compared utilisation of non-native waterweeds Elodea canadensis and E. nuttallii in mono- and polycultures. Furthermore, we quantified de-cased and cased caddisfly-induced fragment production and length changes among non-native E. canadensis, E. nuttallii, Crassula helmsii and Lagarosiphon major under two different plant orientations: horizontal (floating) versus vertical (upright) growth forms. Larval caddisflies exhibited Type II (hyperbolic) FRs towards both Elodea species, and utilised each plant at similar rates when plants were provided separately. When plant species were presented in combination horizontally, E. canadensis was significantly less utilised compared to E. nuttallii, corroborating observations in the field. De-cased larvae produced new plant fragments for all four aquatic macrophytes, whereas cased larvae fragmented plants significantly less. Elodea nuttalii and C. helmsii were fragmented the most overall. Crassula helmsii was utilised to the greatest extent when plants were horizontally orientated, and Elodea species when vertically orientated. This study identifies and quantifies a mechanism from a novel species group that may contribute to the spread of invasive macrophytes in aquatic systems. Whilst exploititative interactions are thought to impede invasion success, here we demonstrate how resource utilisation by a resident species may exacerbate propagule pressure from an invasive species.
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  • 26
    Publication Date: 2021-01-13
    Type: Report , NonPeerReviewed
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  • 27
    Publication Date: 2021-01-13
    Description: Highlights: • We summarized 20 ecosystem services provided by coastal Baltic ecosystems. • Information on how services translate into socio-economic benefits is lacking. • The deep knowledge gap impairs the sustainable management of the benefits. • We propose a framework with four key measures to close this knowledge gap. • Toxins and Nutrients are the most well-document pressures to these services. Abstract: Seagrass meadows, algal forests and mussel beds are widely regarded as foundation species that support communities providing valuable ecosystem services in many coastal regions; however, quantitative evidence of the relationship is scarce. Using the Baltic Sea as a case study, a region of significant socio-economic importance in the northern hemisphere, we systematically synthesized the primary literature and summarized the current knowledge on ecosystem services derived from seagrass, macroalgae, and mussels (see animated video summary of the manuscript: Video abstract). We found 1740 individual ecosystem service records (ESR), 61% of which were related to macroalgae, 26% to mussel beds and 13% to seagrass meadows. The most frequently reported ecosystem services were raw material (533 ESR), habitat provision (262 ESR) and regulation of pollutants (215 ESR). Toxins (356 ESR) and nutrients (302 ESR) were the most well-documented pressures to services provided by coastal ecosystems. Next, we assessed the current state of knowledge as well as knowledge transfer of ecosystem services to policies through natural, social, human and economic dimensions, using a systematic scoring tool, the Eco-GAME matrix. We found good quantitative information about how ecosystems generated the service but almost no knowledge of how they translate into socio-economic benefits (8 out of 657 papers, 1.2%). While we are aware that research on Baltic Sea socio-economic benefits does exist, the link with ecosystems providing the service is mostly missing. To close this knowledge gap, we need a better analytical framework that is capable of directly linking existing quantitative information about ecosystem service generation with human benefit.
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  • 28
    Publication Date: 2021-01-13
    Description: Variation in gene expression contributes to ecological speciation by facilitating population persistence in novel environments. Likewise, immune response can be a relevant factor in speciation driven by adaptation to different environments. Previous studies examining gene expression differences between recently diverged ecotypes often relied on only one pair of populations, targeted the expression of only a subset of genes, or used wild caught‐individuals. Here, we investigated the contribution of habitat‐specific parasites and symbionts and the underlying immunological capabilities of ecotype hosts to adaptive divergence in lake‐river population pairs of the cichlid fish Astatotilapia burtoni. To shed light on the role of phenotypic plasticity in adaptive divergence, we compared parasite and microbiota communities, immune response, and gene expression patterns of fish from natural habitats and a lake‐like pond setup. In all investigated population pairs, lake fish were more heavily parasitized than river fish, both in terms of parasite taxa composition and infection abundance. Innate immune response in the wild was higher in lake than in river populations and elevated in a river population exposed to lake parasites in the pond setup. Environmental differences between lake and river habitat and their distinct parasite communities shaped differential gene expression, involving genes functioning in osmoregulation and immune response. Most changes in gene expression between lake and river samples in the wild and in the pond setup were based on a plastic response. Finally, gene expression and bacterial communities of wild‐caught individuals and individuals acclimated to lake‐like pond conditions showed shifts underlying adaptive phenotypic plasticity.
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  • 29
    Publication Date: 2021-01-13
    Description: Remobilization of soil carbon as a result of permafrost degradation in the drainage basin of the major Siberian rivers combined with higher precipitation in a warming climate potentially increase the flux of terrestrial derived dissolved organic matter (tDOM) into the Arctic Ocean. The Laptev (LS) and East Siberian Seas (ESS) receive enormous amounts of tDOM-rich river water, which undergoes at least one freeze-melt cycle in the Siberian Arctic shelf seas. To better understand how freezing and melting affect the tDOM dynamics in the LS and ESS, we sampled sea ice, river and seawater for their dissolved organic carbon (DOC) concentration and the colored fraction of dissolved organic matter. The sampling took place in different seasons over a period of 9 years (2010–2019). Our results suggest that the main factor regulating the tDOM distribution in the LS and ESS is the mixing of marine waters with freshwater sources carrying different tDOM concentrations. Of particular importance in this context are the 211 km3 of meltwater from land-fast ice from the LS, containing ~ 0.3 Tg DOC, which in spring mixes with 245 km3 of river water from the peak spring discharge of the Lena River, carrying ~ 2.4 Tg DOC into the LS. During the ice-free season, tDOM transport on the shelves takes place in the surface mixed layer, with the direction of transport depending on the prevailing wind direction. In winter, about 1.2 Tg of brine-related DOC, which was expelled from the growing land-fast ice in the LS, is transported in the near-surface water layer into the Transpolar Drift Stream that flows from the Siberian Shelf toward Greenland. The actual water depth in which the tDOM-rich brines are transported, depends mainly on the density stratification of the LS and ESS in the preceding summer and the amount of ice produced in winter. We suspect that climate change in the Arctic will fundamentally alter the dynamics of tDOM transport in the Arctic marginal seas, which will also have consequences for the Arctic carbon cycle.
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  • 30
    Publication Date: 2021-01-13
    Description: For many coastal areas including the Baltic Sea, ambitious nutrient abatement goals have been set to curb eutrophication, but benefits of such measures were normally not studied in light of anticipated climate change. To project the likely responses of nutrient abatement on eelgrass (Zostera marina), we coupled a species distribution model with a biogeochemical model, obtaining future water turbidity, and a wave model for predicting the future hydrodynamics in the coastal area. Using this, eelgrass distribution was modeled for different combinations of nutrient scenarios and future wind fields. We are the first to demonstrate that while under a business as usual scenario overall eelgrass area will not recover, nutrient reductions that fulfill the Helsinki Commission’s Baltic Sea Action Plan (BSAP) are likely to lead to a substantial areal expansion of eelgrass coverage, primarily at the current distribution’s lower depth limits, thereby overcompensating losses in shallow areas caused by a stormier climate.
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  • 31
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    Elsevier
    In:  Marine Pollution Bulletin, 163 . Art.Nr. 111932.
    Publication Date: 2021-01-13
    Description: Highlights • Roughly 250 high-quality lab experiments of oil droplet-size are now available. • Comparisons with observations show the best droplet-size models have confidence limits of ±50%. • Inaccuracies in predicted oil droplet-size can substantially affect calculated fates. • Further improvement of droplet-size models is needed, especially validation at field-scales. Abstract Droplet size substantially affects the fate of oil released from deep subsea leaks. A baseline dataset of volume-median droplet diameters (d50), culled from ~250 laboratory observations, is used to validate seven droplet-size models. Four models compare reasonably well, having 95% confidence limits in d50 of ~±50%. Simulations with a near-field fate model (TAMOC) reveals that the four best-performing models, with d50 of 1.3–2.2 mm, agree similarly with observed fractionation of petroleum compounds in the water column during June 4–July 15, 2010. Model results suggest that, had a higher dose of dispersant been applied at the wellhead during Deepwater Horizon oil spill (DWH), the d50 would have dropped by an order of magnitude, reducing surfacing C1–C9 volatiles by 3.5×. Model uncertainty is found to be substantial for DWH-like blowouts treated with chemical dispersants, suggesting the need for further droplet-size model improvement.
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  • 32
    Publication Date: 2021-01-13
    Description: Highlights • A mechanistic explanation is provided for the observed CO2 loss in the sediments. • Reactions of CO2 with the sediment lead to significant heating. • The observations were modeled including reactions and losses due to lateral transport. • CO2 leakage will lead to very local effects. Abstract We investigated the effect of an artificial CO2 vent (0.0015−0.037 mol s−1), simulating a leak from a reservoir for carbon capture and storage (CCS), on the sediment geochemistry. CO2 was injected 3 m deep into the seafloor at 120 m depth. With increasing mass flow an increasing number of vents were observed, distributed over an area of approximately 3 m. In situ profiling with microsensors for pH, T, O2 and ORP showed the geochemical effects are localized in a small area around the vents and highly variable. In measurements remote from the vent, the pH reached a value of 7.6 at a depth of 0.06 m. In a CO2 venting channel, pH reduced to below 5. Steep temperature profiles were indicative of a heat source inside the sediment. Elevated total alkalinity and Ca2+ levels showed calcite dissolution. Venting decreased sulfate reduction rates, but not aerobic respiration. A transport-reaction model confirmed that a large fraction of the injected CO2 is transported laterally into the sediment and that the reactions between CO2 and sediment generate enough heat to elevate the temperature significantly. A CO2 leak will have only local consequences for sediment biogeochemistry, and only a small fraction of the escaped CO2 will reach the sediment surface.
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  • 33
    Publication Date: 2021-01-13
    Description: One pathway by which the oceans influence climate is via the emission of sea spray that may subsequently influence cloud properties. Sea spray emissions are known to be dependent on atmospheric and oceanic physicochemical parameters, but the potential role of ocean biology on sea spray fluxes remains poorly characterized. Here we show a consistent significant relationship between seawater nanophytoplankton cell abundances and sea-spray derived Cloud Condensation Nuclei (CCN) number fluxes, generated using water from three different oceanic regions. This sensitivity of CCN number fluxes to ocean biology is currently unaccounted for in climate models yet our measurements indicate that it influences fluxes by more than one order of magnitude over the range of phytoplankton investigated.
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  • 34
    Publication Date: 2021-01-13
    Description: Modelling the drift of marine debris in quasi-real time can be of societal relevance. One pertinent example is Malaysia Airlines flight MH370. The aircraft is assumed to have crashed in the Indian Ocean, leaving floating wreckage to drift on the surface. Some of these items were recovered around the western Indian Ocean. We use ocean currents simulated by an operational ocean model in conjunction with surface Stokes drift to determine the possible paths taken by the debris. We consider: (1) How important is the influence of surface waves on the drift? (2) What are the relative benefits of forward- and backward-tracking in time? (3) Does including information from more items refine the most probable crash-site region? Our results highlight a critical contribution of Stokes drift and emphasise the need to know precisely the buoyancy characteristics of the items. The differences between the tracking approaches provide a measure of uncertainty which can be minimised by simulating a sufficiently large number of virtual debris. Given the uncertainties associated with the timings of the debris sightings, we show that at least 5 items are required to achieve an optimal most probable crash-site region. The results have implications for other drift simulation applications.
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  • 35
    Publication Date: 2021-01-13
    Description: Marine mammals and the ecological functions they provide to coastal and pelagic ecosystems are increasingly threatened by the intensification of anthropogenic impacts. The Uruguayan coastline throughout the 20th century, like other coastal environments worldwide, has been the sink of a variety of trace metals derived from the rapid urbanization and industrialization of related land areas. This coastline is inhabited by two species of pinnipeds trophically and spatially segregated. Otaria byronia feeds in coastal environments while Arctocephalus australis preysmainly offshore. The present study aimed to analyze historic changes in concentrations of trace elements in teeth of both species from 1941 to the present day. We analyzed the dentin of 94 canine teeth using stable isotope analysis (delta C-13) and ICP-MS to determine their feeding areas and the concentration of 10 trace elements (Al, As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) respectively. The concentration of Cr was significantly higher during '70-'80s, in both species coinciding with tannery industry development. Both species of pinnipeds have been differentially exposed to trace elements depending on their feeding area. A pelagic diet, possibly based on squid, increased the concentration of Cd in A. australis, while O. byronia has been more exposed to anthropogenic Pb and Cu associated to a costal and more benthic diet. Our results highlight dentin as a reliable matrix for historic studies on the exposure to trace elements. In light of our results, the O. byronia's declining population could be the result of the synergistic effects of trace elements together with other ecological pressures faced in their environment.
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  • 36
    Publication Date: 2021-01-13
    Description: Highlights • Core-log-seismic correlation allows to assign ages to the Scotia Sea seismic record. • Major implications are derived on the relation between regional and global events. • The main stratigraphic events are much younger than previously proposed. • Three major phases for the regional oceanography are observed from late Miocene. • These phases appear to be closely linked to the Antarctic Ice Sheet dynamics. Scotia Sea and the Drake Passage is key towards understanding the development of modern oceanic circulation patterns and their implications for ice sheet growth and decay. The sedimentary record of the southern Scotia Sea basins documents the regional tectonic, oceanographic and climatic evolution since the Eocene. However, a lack of accurate age estimations has prevented the calibration of the reconstructed history. The upper sedimentary record of the Scotia Sea was scientifically drilled for the first time in 2019 during International Ocean Discovery Program (IODP) Expedition 382, recovering sediments down to ∼643 and 676 m below sea floor in the Dove and Pirie basins respectively. Here, we report newly acquired high resolution physical properties data and the first accurate age constraints for the seismic sequences of the upper sedimentary record of the Scotia Sea to the late Miocene. The drilled record contains four basin-wide reflectors – Reflector-c, -b, -a and -a' previously estimated to be ∼12.6 Ma, ∼6.4 Ma, ∼3.8 Ma and ∼2.6 Ma, respectively. By extrapolating our new Scotia Sea age model to previous morpho-structural and seismic-stratigraphic analyses of the wider region we found, however, that the four discontinuities drilled are much younger than previously thought. Reflector-c actually formed before 8.4 Ma, Reflector-b at ∼4.5/3.7 Ma, Reflector-a at ∼1.7 Ma, and Reflector-a' at ∼0.4 Ma. Our updated age model of these discontinuities has major implications for their correlation with regional tectonic, oceanographic and cryospheric events. According to our results, the outflow of Antarctic Bottom Water to northern latitudes controlled the Antarctic Circumpolar Current flow from late Miocene. Subsequent variability of the Antarctic ice sheets has influenced the oceanic circulation pattern linked to major global climatic changes during early Pliocene, Mid-Pleistocene and the Marine Isotope Stage 11.
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  • 37
    Publication Date: 2021-01-13
    Description: This study presents culture experiments of the cold water species Neogloboquadrina pachyderma (sinistral) and provides new insights into the incorporation of elements in foraminiferal calcite of common and newly established proxies for paleoenvironmental applications (shell Mg/Ca, Sr/Ca and Na/Ca). Specimens were collected from sea ice during the austral winter in the Antarctic Weddell Sea and subsequently cultured at different salinities and a constant temperature. Incorporation of the fluorescent dye calcein showed new chamber formation in the culture at salinities of 30, 31, and 69. Cultured foraminifers at salinities of 46 to 83 only revealed chamber wall thickening, indicated by the fluorescence of the whole shell. Signs of reproduction and the associated gametogenic calcite were not observed in any of the culture experiments. Trace element analyses were performed using an electron microprobe, which revealed increased shell Mg/Ca, Sr/Ca, and Na/Ca values at higher salinities, with Mg/Ca showing the lowest sensitivity to salinity changes. This study enhances the knowledge about unusually high element concentrations in foraminifera shells from high latitudes. Neogloboquadrina pachyderma appears to be able to calcify in the Antarctic sea ice within brine channels, which have low temperatures and exceptionally high salinities due to ongoing sea ice formation.
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  • 38
    Publication Date: 2021-01-13
    Description: Measurements of free amino acids (FAAs) in the marine environment to elucidate their transfer from the ocean into the atmosphere, to marine aerosol particles and to clouds, were performed at the MarParCloud (marine biological production, organic aerosol particles and marine clouds: a process chain) campaign at the Cabo Verde islands in autumn 2017. According to physical and chemical specifications such as the behavior of air masses, particulate MSA concentrations and MSA∕sulfate ratios, as well as particulate mass concentrations of dust tracers, aerosol particles predominantly of marine origin with low to medium dust influences were observed. FAAs were investigated in different compartments: they were examined in two types of seawater underlying water (ULW) and in the sea surface microlayer (SML), as well as in ambient marine size-segregated aerosol particle samples at two heights (ground height based at the Cape Verde Atmospheric Observatory, CVAO, and at 744 m height on Mt. Verde) and in cloud water using concerted measurements. The ∑FAA concentration in the SML varied between 0.13 and 3.64 µmol L−1, whereas it was between 0.01 and 1.10 µmol L−1 in the ULW; also, a strong enrichment of ∑FAA (EFSML: 1.1–298.4, average of 57.2) was found in the SML. In the submicron (0.05–1.2 µm) aerosol particles at the CVAO, the composition of FAAs was more complex, and higher atmospheric concentrations of ∑FAA (up to 6.3 ng m−3) compared to the supermicron (1.2–10 µm) aerosol particles (maximum of 0.5 ng m−3) were observed. The total ∑FAA concentration (PM10) was between 1.8 and 6.8 ng m−3 and tended to increase during the campaign. Averaged ∑FAA concentrations in the aerosol particles on Mt. Verde were lower (submicron: 1.5 ng m−3; supermicron: 1.2 ng m−3) compared to the CVAO. A similar contribution percentage of ∑FAA to dissolved organic carbon (DOC) in the seawater (up to 7.6 %) and to water-soluble organic carbon (WSOC) in the submicron aerosol particles (up to 5.3 %) indicated a related transfer process of FAAs and DOC in the marine environment. Considering solely ocean–atmosphere transfer and neglecting atmospheric processing, high FAA enrichment factors were found in both aerosol particles in the submicron range (EFaer(∑FAA): 2×103–6×103) and medium enrichment factors in the supermicron range (EFaer(∑FAA): 1×101–3×101). In addition, indications for a biogenic FAA formation were observed. Furthermore, one striking finding was the high and varying FAA cloud water concentration (11.2–489.9 ng m−3), as well as enrichments (EFCW: 4×103 and 1×104 compared to the SML and ULW, respectively), which were reported here for the first time. The abundance of inorganic marine tracers (sodium, methanesulfonic acid) in cloud water suggests an influence of oceanic sources on marine clouds. Finally, the varying composition of the FAAs in the different matrices shows that their abundance and ocean–atmosphere transfer are influenced by additional biotic and abiotic formation and degradation processes. Simple physicochemical parameters (e.g., surface activity) are not sufficient to describe the concentration and enrichments of the FAAs in the marine environment. For a precise representation in organic matter (OM) transfer models, further studies are needed to unravel their drivers and understand their composition.
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  • 39
    Publication Date: 2021-01-13
    Description: Red yeasts of the genus Rhodotorula are of great interest to the biotechnological industry due to their ability to produce valuable natural products, such as lipids and carotenoids with potential applications as surfactants, food additives, and pharmaceuticals. Herein, we explored the biosynthetic potential of R. mucilaginosa 50-3-19/20B collected from the Mid-Atlantic Ridge using modern genomics and untargeted metabolomics tools. R. mucilaginosa 50-3-19/20B exhibited anticancer activity when grown on PDA medium, while antimicrobial activity was observed when cultured on WSP-30 medium. Applying the bioactive molecular networking approach, the anticancer activity was linked to glycolipids, namely polyol esters of fatty acid (PEFA) derivatives. We purified four PEFAs (1–4) and the known methyl-2-hydroxy-3-(1H-indol-2-yl)propanoate (5). Their structures were deduced from NMR and HR-MS/MS spectra, but 1–5 showed no anticancer activity in their pure form. Illumina-based genome sequencing, de novo assembly and standard biosynthetic gene cluster (BGC) analyses were used to illustrate key components of the PEFA biosynthetic pathway. The fatty acid producing BGC3 was identified to be capable of producing precursors of PEFAs. Some Rhodotorula strains are able to convert inulin into high-yielding PEFA and cell lipid using a native exo-inulinase enzyme. The genomic locus for an exo-inulinase enzyme (g1629.t1), which plays an instrumental role in the PEFA production via the mannitol biosynthesis pathway was identified. This is the first untargeted metabolomics study on R. mucilaginosa providing new genomic insights into PEFA biosynthesis.
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  • 40
    Publication Date: 2021-01-13
    Description: Aim: The spread of invasive non‐native species (INNS) will pose major threats to global biodiversity over the coming decades. However, predicting how key effects of climate change will influence the abilities of INNS to establish and exert ecological impact is a major challenge. One overlooked aspect of global change is the expected freshening of certain marine systems, which may interact with INNS and lead to drastic effects on community structure and stability. Location: Baltic Sea, Europe. Methods: Here, using three predatory amphipod crustaceans, we experimentally assessed how salinity reduction may affect the impacts of the emerging INNS, Pontogammarus maeoticus, relative to an existing INNS, Gammarus tigrinus and a trophically analogous native, Gammarus salinus. We quantified per capita impacts of the three species via the comparative functional response method (prey consumption over a range of prey densities) under a predicted seawater freshening scenario. We then combined amphipod functional responses with their life history traits to compare population‐level relative impact potential (RIP) on prey of the three amphipod species across salinities. Results: Freshening substantially altered the predicted relative ecological impacts of both the INNS compared with the native. First, the functional responses of invasive P. maeoticus and G. tigrinus increased under freshening, while that of the native G. salinus decreased. Second, RIP became consistently higher for both the INNS compared to the native with increased freshening. Main conclusions: Our methods thus reveal potential for climate change via seawater freshening to drive large shifts in dominance and ecological impacts of INNS compared with natives. With the number of INNS introductions unlikely to saturate in the near future, we highlight the need to assess the impacts of potential future INNS, alongside established non‐natives and native species, in combination with abiotic changes associated with climate change.
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  • 41
    Publication Date: 2021-01-13
    Description: The unknown status of inland fish stocks hinders their sustainable management. Therefore, increasing stock status information is important for sustainable inland fisheries. Fisheries reference points were estimated for five exploited fish species (11 stocks) in the Lake Edward system, East Africa, which is one of the most productive inland water systems. The aim was to ascertain the status of the fisheries and establish reference points for effective management. The reference points were based on four linked stock assessment approaches for data‐limited fisheries. Estimates showed poor stock status with the stocks defined as either collapsed, recruitment impaired or overfished. However, higher catches could be obtained under sustainable management. Estimates of maximum sustainable yield (MSY) and supporting biomass (Bmsy) are provided for 10 of the stocks as targets for rebuilding plans. The immediate target of management should be rebuilding biomass to Bmsy. Applicable measures include shifting length at first capture to the length that maximizes catch without endangering size structure and biomass, and livelihood diversification out of fisheries.
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  • 42
    Publication Date: 2021-01-13
    Description: Highlights: • Fan-shaped sponges display panmixia at three locations in the Cantabrian Sea. • Subtle sponge population genetic and pronounced microbial differences were observed between a canyon and bank (〈100km apart). • Lagrangian modelling reveals variable inter-annual connectivity via ocean currents between the sampling regions. • Interdisciplinary approaches can help to improve understanding about connectivity in the deep-sea. Abstract: Connectivity is a fundamental process driving the persistence of marine populations and their adaptation potential in response to environmental change. In this study, we analysed the population genetics of two morphologically highly similar deep-sea sponge clades (Phakellia hirondellei and the ‘Topsentia-and-Petromica’ clade, (hereafter referred to as ‘TaP clade’)) at three locations in the Cantabrian Sea and simultaneously assessed the corresponding host microbiome by 16S rRNA gene sequencing. A virtual particle tracking approach (Lagrangian modelling) was applied to assess oceanographic connectivity in the study area. We observed overall genetic uniformity for both sponge clades. Notably, subtle genetic differences were observed for sponges of the TaP clade and also their microbiomes between a canyon and bank location, 〈 100 km apart and with the same depth range. The Lagrangian model output suggests a strong retention of larvae in the study area with variable inter-annual connectivity via currents between the three sampling regions. We conclude that geologic features (canyons) and the prevailing ocean currents may dictate sponge holobiont connectivity and that differentiation can emerge even on small spatial scales.
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  • 43
    Publication Date: 2021-01-13
    Description: Marine sponges are exceptionally prolific sources of natural products for the discovery and development of new drugs. Until now, sponges have contributed around 30% of all natural metabolites isolated from the marine environment. Family Latrunculiidae Topsent, 1922 (class Demospongiae Sollas, 1885, order Poecilosclerida Topsent, 1928) is a small sponge family comprising seven genera. Latrunculid sponges are recognized as the major reservoirs of diverse types of pyrroloiminoquinone-type alkaloids, with a myriad of biological activities, in particular, cytotoxicity, fuelling their exploration for anticancer drug discovery. Almost 100 pyrroloiminoquinone alkaloids and their structurally related compounds have been reported from the family Latrunculiidae. The systematics of latrunculid sponges has had a complex history, however it is now well understood. The pyrroloiminoquinone alkaloids have provided important chemotaxonomic characters for this sponge family. Latrunculid sponges have been reported to contain other types of metabolites, such as peptides (callipeltins), norditerpenes and norsesterpenes (trunculins) and macrolides (latrunculins), however, the sponges containing latrunculins and trunculins have been transferred to other sponge families. This review highlights a comprehensive literature survey spanning from the first chemical investigation of a New Zealand Latrunculia sp. in 1986 until August 2020, focusing on the chemical diversity and biological activities of secondary metabolites reported from the family Latrunculiidae. The biosynthetic (microbial) origin and the taxonomic significance of pyrroloiminoquinone related alkaloids are also discussed.
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  • 44
    facet.materialart.
    Unknown
    In:  (PhD/ Doctoral thesis), Christian-Albrechts-Universität, Kiel, 184 pp
    Publication Date: 2021-01-14
    Type: Thesis , NonPeerReviewed
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  • 45
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    Springer
    In:  (In Press / Accepted) Environmental Science and Pollution Research .
    Publication Date: 2021-01-15
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  • 46
    Publication Date: 2021-01-15
    Description: Highlights: • Microplastics were found at all of the 15 North German farmland sites sampled. • Mean microplastics' abundance was 3.7 ± 11.9 MP particles per kg DW (median: 0.0, interquartile range: 0.0–4.9). • Composition of microplastics was uniform across the farmland sites sampled. • The most abundant particles were black films made of polyethylene. • Microplastic pollution decreased with soil depths despite regular ploughing. Abstract: The pollution of the aquatic and terrestrial environment with plastics is a fast growing phenomenon with potential threats to the functioning of ecosystems and organisms therein as well as for human well-being. So far, research activities have mainly focused on the occurrence of microplastics (MP) in marine habitats, while little is known about their distribution and composition in the terrestrial environment. Agricultural practices such as fertilization, mulching or ensilage make agriculture a likely path for MP into the environment. Here, we collected soil samples at 15 farmland locations in Schleswig-Holstein, Northern Germany, to study the amount, distribution and composition of MP in the size range between 1 and 5 mm. In total, 379 MP were identified in a total of ~84 kg of dry weight (DW). Particle abundances in the sampling units ranged from 0 to 217.8 MP per kg DW with a mean abundance of 3.7 ± 11.9 MP per kg DW (median: 0.0, interquartile range: 0.0–4.9) per site. Although MP were found at all study sites, only 34% of the sampling units contained synthetic particles. Our data contribute to the establishment of a baseline on the amount, type and size of MP in farmland soils. Such a baseline is important for future monitoring schemes and for the development of more environmentally friendly management systems that reduce the input of MP into the agricultural system.
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  • 47
    Publication Date: 2021-01-15
    Description: Splitting of the Vitiaz arc formed the Tonga-Kermadec and Lau-Colville Ridges (southwestern Pacific Ocean), separated by the Lau Basin in the north and Havre Trough in the south. We present new trace element and Sr-Nd-Hf-Pb isotope geochemistry for the Kermadec and Colville Ridges extending ~900 km north of New Zealand (36°S–28°S) in order to (1) compare the composition of the arc remnants with Quaternary Kermadec arc volcanism, (2) constrain spatial geochemical variations in the arc remnants, (3) evaluate the effect of Hikurangi igneous plateau subduction on the geochemistry of the older arc lavas, and (4) elucidate what may have caused arc splitting. Compared to the Kermadec Ridge, the Colville Ridge has higher more-incompatible to less-incompatible immobile element ratios and largely overlapping isotope ratios, consistent with an origin through lower degrees of melting of more enriched upper mantle in the Vitiaz rear arc. Between ca. 8 and 3 Ma, both halves of the arc (~36°S–29°S) included a more enriched (EM1-type) composition (with lower 206Pb/204Pb and 207Pb/204Pb and higher Δ8/4 Pb [deviation of the measured 208Pb/204Pb ratio from a Northern Hemisphere basalt regression line] and 87Sr/86Sr) compared to older and younger arc lavas. High-Ti basalts from the Manihiki Plateau, once joined to the Hikurangi Plateau, could serve as the enriched Vitiaz arc end member. We propose that the enriched plateau signature, seen only in the isotope ratios of mobile elements, was transported by hydrous fluids from the western margin of the subducting Hikurangi Plateau or a Hikurangi Plateau fragment into the overlying mantle wedge. Our results are consistent with plateau subduction triggering arc splitting and backarc opening.
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  • 48
    Publication Date: 2021-01-15
    Description: The Atlantic Niño is the leading mode of interannual sea-surface temperature (SST) variability in the equatorial Atlantic and assumed to be largely governed by coupled ocean-atmosphere dynamics described by the Bjerknes-feedback loop. However, the role of the atmospheric diabatic heating, which can be either an indicator of the atmosphere’s response to, or its influence on the SST, is poorly understood. Here, using satellite-era observations from 1982–2015, we show that diabatic heating variability associated with the seasonal migration of the Inter-Tropical Convergence Zone controls the seasonality of the Atlantic Niño. The variability in precipitation, a measure of vertically integrated diabatic heating, leads that in SST, whereas the atmospheric response to SST variability is relatively weak. Our findings imply that the oceanic impact on the atmosphere is smaller than previously thought, questioning the relevance of the classical Bjerknes-feedback loop for the Atlantic Niño and limiting climate predictability over the equatorial Atlantic sector.
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  • 49
    Publication Date: 2021-01-15
    Description: We present results from an ensemble of eight climate models, each of which has carried out simulations of the early Eocene climate optimum (EECO, ∼ 50 million years ago). These simulations have been carried out in the framework of the Deep-Time Model Intercomparison Project (DeepMIP; http://www.deepmip.org, last access: 10 January 2021); thus, all models have been configured with the same paleogeographic and vegetation boundary conditions. The results indicate that these non-CO2 boundary conditions contribute between 3 and 5 ∘C to Eocene warmth. Compared with results from previous studies, the DeepMIP simulations generally show a reduced spread of the global mean surface temperature response across the ensemble for a given atmospheric CO2 concentration as well as an increased climate sensitivity on average. An energy balance analysis of the model ensemble indicates that global mean warming in the Eocene compared with the preindustrial period mostly arises from decreases in emissivity due to the elevated CO2 concentration (and associated water vapour and long-wave cloud feedbacks), whereas the reduction in the Eocene in terms of the meridional temperature gradient is primarily due to emissivity and albedo changes owing to the non-CO2 boundary conditions (i.e. the removal of the Antarctic ice sheet and changes in vegetation). Three of the models (the Community Earth System Model, CESM; the Geophysical Fluid Dynamics Laboratory, GFDL, model; and the Norwegian Earth System Model, NorESM) show results that are consistent with the proxies in terms of the global mean temperature, meridional SST gradient, and CO2, without prescribing changes to model parameters. In addition, many of the models agree well with the first-order spatial patterns in the SST proxies. However, at a more regional scale, the models lack skill. In particular, the modelled anomalies are substantially lower than those indicated by the proxies in the southwest Pacific; here, modelled continental surface air temperature anomalies are more consistent with surface air temperature proxies, implying a possible inconsistency between marine and terrestrial temperatures in either the proxies or models in this region. Our aim is that the documentation of the large-scale features and model–data comparison presented herein will pave the way to further studies that explore aspects of the model simulations in more detail, for example the ocean circulation, hydrological cycle, and modes of variability, and encourage sensitivity studies to aspects such as paleogeography, orbital configuration, and aerosols.
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  • 50
    Publication Date: 2021-01-18
    Description: Chirp sub-bottom profilers (SBP) provide centi-to-decimetre resolution, seismic data with applications for various geophysical and geological purposes. To verify the field application of imaging of a buried target with a cost-effective and easy-to-apply pseudo-3D Chirp SBP survey, we explored the buried site of an ancient wooden shipwreck off the west coast of Korea before underwater excavations. The survey was conducted using a commercial 2D Chirp SBP system with a newly devised recording system that preserved the true polarity of the chirp signal. To produce high-resolution 3D Chirp SBP data from 2D Chirp SBP datasets recorded by the novel system, an optimal data processing sequence, consisting of a first phase of 2D data processing and a second phase of 3D data processing was designed. The first, 2D phase, included the estimation of a source sweep signature, cross-correlation, and deconvolution using an inverse filter. The resulting resolution of the 2D Chirp SBP data was better than that of the enveloped data provided by the commercial acquisition system. The second phase of 3D data processing included gathering 3D datasets, redistributing of ping positions, and static correction. To improve the consistency of the seismic events and reduce the repetitive corrections (swell, tidal, tie, and residual corrections), a static correction was based on multi-beam echo sounder data. The amplitude variation near the shipwreck was clearly apparent in the time slice from the final pseudo-3D Chirp SBP dataset with a bin size of 2.0 m (crossline) × 0.6 m (inline). Through 3D rendering, the buried ancient shipwreck with dimensions of 5 m (width) × 12 m (length) × 2 m (depth) was imaged successfully.
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  • 51
    Publication Date: 2021-01-18
    Description: The substance Tris (or THAM, 2-amino-2-hydroxymethyl-1,3-propanediol) is used in the preparation of pH buffer solutions for applications in natural water chemistry, including seawater. The development of a chemical speciation model of buffer solutions containing Tris, TrisH+, and the major ions of seawater is desirable, so that the effects of changes in the composition and concentration of the medium on pH can be calculated. The Pitzer activity coefficient equations, commonly used in such speciation models, describe the thermodynamic properties of solutions in terms of interactions between dissolved ions and uncharged solute species. To determine some of these interactions, we have measured solubilities of Tris(s) in water and aqueous solutions of NaCl, TrisHCl, and (TrisH)2SO4 and the solubility of NaCl(s) in aqueous Tris(aq), from 5 to 45 °C. We report measurements of the water activities of Tris solutions at 293.5 K to high supersaturation with respect to the solid. Using the Pitzer equations, we compare our results to literature data yielding stoichiometric dissociation constants of TrisH+ in aqueous NaCl, and to electromotive forces of cells containing dissolved Tris, TrisHCl, and NaCl. Values of parameters for the interactions of Tris with the ions TrisH+, Na+, and SO42– at 25 °C are determined.
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  • 52
    Publication Date: 2021-01-18
    Description: Highlights • Loess in Northern Iran sensitively reacted on Pleistocene climate change. • Dust accumulation and soil formation followed climate cycles of the Northern Hemisphere. • Pedostratigraphic correlation provides link within Southern Eurasian loess belt. • Southern Caspian Lowlands provide key area for climate reconstruction in West Asia. The southern Caspian Lowland sensitively reacted to Pleistocene climate change and is a key area for reconstructing climate dynamics and landscape evolution in Southern Eurasia. Loess-paleosol sequences (LPS) of the northern foothills of Alborz Mountains provide detailed records of climate-induced changes of dust accumulation and soil formation correlating with relatively dry or moist conditions of the past. The LPS at Neka-Abelou (NA) was studied in detail in order to understand these dynamics and provide a base for regional pedostratigraphic correlation. We have carried out high-resolution analyses of grain-size, sediment color, mass specific and frequency-dependent magnetic susceptibility and carbonate content and established a temporal framework as based on luminescence dating using a post-IR infrared stimulated luminescence (pIRIR) protocol and fading corrections. The LPS of NA is composed of finely textured loess, which is subdivided by at least eleven paleosols. Moreover, it contains a thin loess layer with lenses of trachytic tephra which most likely originated from the Damavand volcano and was deposited during Marine Isotope Stage (MIS) 4. The lower part of the LPS at NA consists of four strongly-developed reddish-brown paleosols (Bt, Btg horizons) separated by thin layers of pedogenically-altered loess indicating moist climate conditions and low dust accumulation rates during the Middle Pleistocene or earlier. The central part contains a pedocomplex of clay-rich paleosols composed of well developed Bt, ABk and Bw horizons formed under strongly reduced dust accumulation rates and intercalated by loess layers. Pedostratigraphic reasoning suggests that this pedocomplex formed during MIS 5, which is corroborated by luminescence dating. The pedocomplex reflects precession time scale climate change and represents an excellent pedostratigraphic marker recognized in numerous exposures along the northern foothills of the Alborz Mountains. The upper part of the LPS accumulated during the Last Pleniglacial and contains probably six weakly developed synsedimentary paleosols (CBk horizons) as well as the modern soil (Bt horizon). Magnetic susceptibility records show very close similarity with the pleniglacial sequence of the LPS at Toshan located about 100 km farther to the east of the Caspian Lowlands suggesting that the weak paleosols at both locations have formed synchronously, which is supported by luminescence dating. Their presence thus reflects at least a regional-scale climate change between dry phases and those of slightly increased edaphic moisture with ongoing dust supply. The LPS of the Caspian Lowlands document a multitude of changes between dominance of dust accumulation or pedogenesis controlled by moisture availability in the context of Pleistocene climate change. The proposed regional pedostratigraphy for the Late Quaternary provides a scheme for large-scale stratigraphic correlation and reconstruction of climate change in Southern Eurasia.
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  • 53
    Publication Date: 2021-01-18
    Description: Highlights • Atlantic and Mediterranean water-mass interface depth affected coral mound growth. • Sapropel derived events had a detrimental influence on coral mound development. • A shift in the reef-building dominating coral species occurred during the Holocene. • The southern mound has been subjected to less favourable environmental conditions. Abstract Cold-water coral mounds are key hot-spots of deep ocean biodiversity and also important archives of past climatic conditions. Nonetheless, the paleo-oceanographic setting in which coral mounds developed in the Mediterranean Sea during the last 500 ka still needs to be properly understood. This study describes the coral deposits and corresponding ages of two on-mound gravity cores acquired from opposite sectors of the newly discovered Cabliers Coral Mound Province (CMP, Alboran Sea, W Mediterranean). U–Th data revealed Pleistocene-aged corals covering mound formation periods from 〉389 to 9.3 ka BP and from 13.7 to 0.3 ka BP in the southern and northern mounds respectively. The coral-rich deposits of the cores were mainly dominated by Desmophyllum pertusum, although in some sections concurrent with the Middle Pleistocene and the Holocene, other corals such as Dendrophyllia cornigera and Madrepora oculata also appeared as dominating species. Coral mound formation stages generally occurred during deglacials and temperate interstadial (3.5–4.1 δ18O‰) periods, whereas during interglacials (〈3.5 δ18O‰) coral mound formation only occurred in the northern and shallower mound. We interpret this to indicate that the shoaling of the interface between Atlantic (AW) and Levantine Intermediate Waters (LIW) during interglacial periods prevented the corals in the southern CMP from acquiring sufficient food supply, thus causing periods of coral mound stagnation. Similarly, the interruption in LIW formation throughout sapropel events also coincides with coral mound stagnation phases. This suggests that sapropel-derived processes, which originated in the eastern Mediterranean, likely affected the entire Mediterranean basin and further supports the role of LIW as a conveyor belt facilitating cold-water coral growth in the Mediterranean Sea. Overall, we show that these coral mounds yield important insights into how local changes in oceanographic conditions can influence coral mound development.
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  • 54
    Publication Date: 2021-01-18
    Description: Highlights • New broad band magnetotelluric data covering the whole Gran Canaria island. • First 3D electrical resistivity model of Gran Canaria island at crustal scale. • Low resistivity anomalies found may be of interest for geothermal exploitation. • 3D electrical resitivity shows a good correlation with other geophysical data available at crustal scale. Abstract Gran Canaria, one of the two main islands of the Canary Archipelago off NW Africa, has been volcanically active for at least 15 million years. The island went through several volcanic cycles that varied greatly in composition and extrusive and intrusive activity. The complex orography of the island has excluded extensive land geophysical surveys on the island. A review of the available geophysical information on the island shows that it has been obtained mainly through marine and airborne geophysical surveys. A new dataset comprising 100 magnetotelluric soundings acquired on land has been used to obtain the first 3D electrical resistivity model of the island at crustal scale. The model shows high resistivity values close to the surface in the exposed Tejeda Caldera that extends at depth to the SE cutting the islands in half. Outside the inferred limits of the Tejeda Caldera the 3D model shows low resistivity values that could be explained by hydrothermal alteration at deeper levels and the presence of marine saltwater intrusion at shallower levels near the coast. The presence of unconnected vertical-like structures, with very low resistivity (〈10 ohm m) could be associated to small convective cells is confirmed by the sensitivity analysis carried out in the present study. Those structures are the most likely candidates for a detailed analysis in order to determine their geothermal economic potential. A comprehensive review of existing geophysical data and models of Gran Canaria island and their comparison with the new 3D electrical resistivity model is presented.
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  • 55
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    GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel
    In:  GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel, 2 pp.
    Publication Date: 2021-01-18
    Description: TRANSFORMERS ; Emden, Deutschland (11.01.2021) – Emden, Deutschland (14.02.2021)
    Type: Report , NonPeerReviewed
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  • 56
    Publication Date: 2021-01-18
    Description: The climactic Los Chocoyos (LCY) eruption from Atitlán caldera (Guatemala) is a key chronostratigraphic marker for the Quaternary period given the extensive distribution of its deposits that reached both the Pacific and Atlantic Oceans. Despite LCY tephra being an important marker horizon, a radioisotopic age for this eruption has remained elusive. Using zircon (U–Th)/He geochronology, we present the first radioisotopically determined eruption age for the LCY of 75 ± 2 ka. Additionally, the youngest zircon crystallization 238U–230Th rim ages in their respective samples constrain eruption age maxima for two other tephra units that erupted from Atitlán caldera, W-Fall (130 +16/−14 ka) and I-Fall eruptions (56 +8.2/−7.7 ka), which under- and overlie LCY tephra, respectively. Moreover, rim and interior zircon dating and glass chemistry suggest that before eruption silicic magma was stored for 〉80 kyr, with magma accumulation peaking within ca. 35 kyr before the LCY eruption during which the system may have developed into a vertically zoned magma chamber. Based on an updated distribution of LCY pyroclastic deposits, a new conservatively estimated volume of ~1220 ± 150 km3 is obtained (volcanic explosivity index VEI 〉 8), which confirms the LCY eruption as the first-ever recognized supereruption in Central America.
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  • 57
    Publication Date: 2021-01-18
    Description: Groundwater-derived solute fluxes to the ocean have long been assumed static and subordinate to riverine fluxes, if not neglected entirely, in marine isotope budgets. Here we present concentration and isotope data for Li, Mg, Ca, Sr, and Ba in coastal groundwaters to constrain the importance of groundwater discharge in mediating the magnitude and isotopic composition of terrestrially derived solute fluxes to the ocean. Data were extrapolated globally using three independent volumetric estimates of groundwater discharge to coastal waters, from which we estimate that groundwater-derived solute fluxes represent, at a minimum, 5% of riverine fluxes for Li, Mg, Ca, Sr, and Ba. The isotopic compositions of the groundwater-derived Mg, Ca, and Sr fluxes are distinct from global riverine averages, while Li and Ba fluxes are isotopically indistinguishable from rivers. These differences reflect a strong dependence on coastal lithology that should be considered a priority for parameterization in Earth-system models.
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  • 58
    facet.materialart.
    Unknown
    Elsevier
    In:  Journal of African Earth Sciences, 174 . Art.Nr. 104055.
    Publication Date: 2021-01-21
    Description: Highlights • Leucogranites from the Donkerhoek batholith (Namibia) are 530.6 ± 08 Ma old. • Leucogranites were generated from Kalahari craton basement rocks. • Extensive crystal fractionation, accumulation and assimilation modified the leucogranites. • The study highlights incremental growth of large-scale batholiths over ~30 Ma. Abstract Syn-tectonic 530.6 ± 0.8 Ma pegmatites and aplites from the Donkerhoek batholith in the Damara orogen (Namibia) are moderately to strongly peraluminous, ferroan, alkalic to calc-alkalic leucogranites. Major and trace element variations and strongly fractionated REE patterns with positive Eu anomalies indicate that the leucogranites represent highly fractionated melts that accumulated or retained feldspar that may account, in part, for their alkalic composition. Elemental variations imply that biotite, garnet, and feldspar were the main fractionating minerals. The pegmatites have lower 87Sr/86Sr (0.7053–0.7097) than—but similar unradiogenic initial εNd (−4.1 to −10) to—the least evolved Donkerhoek granites. Two aplites have similar εNd values but unreasonably unradiogenic 87Sr/86Sr ratios as a result of late-stage disturbance and associated overcorrection due to their extremely high 87Rb/86Sr ratios. Subtle variation in Nd isotope compositions coupled with LREE fractionation indicate limited AFC or contamination processes. Lead isotope compositions are more radiogenic than those from published Donkerhoek samples, indicating derivation from or involvement of a component with a considerable crustal residence time. Based on the alkalic to calc-alkalic and ferroan composition and the similarity in Nd–Sr isotopes, meta-igneous basement rocks from the nearby Kalahari craton are likely sources. This study confirms previous studies on the Donkerhoek batholith that have shown that giant batholiths consist of distinct magma batches that are derived from various sources. The new age constraints in conjunction with published ages show that the large-scale Donkerhoek batholith, with a spatial extent of 〉5000 km2, grew incrementally over a period of at least 30 Myr.
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  • 59
    Publication Date: 2021-01-21
    Description: In the Comechingones pegmatitic field, central Argentina, leucogranite and pegmatite bodies crop out in a relatively narrow (25 × 10 km) belt, and were emplaced synkinematically with the main deformational event of the crustal-scale Guacha Corral shear zone during the Early Ordovician (~ 475 Ma). These leucogranites and pegmatites are geochemically evolved rocks with high silica and alkalis, low Fe2O3, MgO, TiO2 and CaO, and high ASI values. The leucogranites display quite variable Sr and Nd isotope compositions (initial 87Sr/86Sr ratios from 0.7048 to 0.7170, and εNd values from + 2.0 to − 3.1), some of which do not overlap with almost any other pre-Famatinian rock from the Sierras de Córdoba. The major and trace element geochemistry and the particular Sr and Nd isotope compositions of the leucogranites are here explained by the following processes: (1) water-fluxed partial melting of amphibolites at relatively low P–T conditions generating currently unexposed granodioritic melts with unradiogenic 87Sr/86Sr ratios and radiogenic εNd values; (2) fractionation of mostly plagioclase and monazite leading to compositions close to the leucogranite melts; and (3) assimilation of metasedimentary rocks with crustal isotopic signatures, modelled by assimilation and fractional crystallization processes. The major, trace and isotope compositions of the pegmatites suggest a derivation from partial melting of the same metasedimentary protoliths of the Sierras de Córdoba that were assimilated by leucogranite melts. We propose a feedback relationship among deformation, anatexis, magma evolution and mass transfer in the context of such a crustal-scale shear zone in the foreland of the Famatinian orogen.
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  • 60
    Publication Date: 2021-01-21
    Description: Subduction zones may develop submarine spreading centers that occur on the overriding plate behind the volcanic arc. In these back-arc settings, the subducting slab controls the pattern of mantle advection and may entrain hydrous melts from the volcanic arc or slab into the melting region of the spreading ridge. We recorded seismic data across the Western Mariana Ridge (WMR, northwestern Pacific Ocean), a remnant island arc with back-arc basins on either side. Its margins and both basins show distinctly different crustal structure. Crust to the west of the WMR, in the Parece Vela Basin, is 4–5 km thick, and the lower crust indicates seismic P-wave velocities of 6.5–6.8 km/s. To the east of the WMR, in the Mariana Trough Basin, the crust is ~7 km thick, and the lower crust supports seismic velocities of 7.2–7.4 km/s. This structural diversity is corroborated by seismic data from other back-arc basins, arguing that a chemically diverse and heterogeneous mantle, which may differ from a normal mid-ocean-ridge–type mantle source, controls the amount of melting in back-arc basins. Mantle heterogeneity might not be solely controlled by entrainment of hydrous melt, but also by cold or depleted mantle invading the back-arc while a subduction zone reconfigures. Crust formed in back-arc basins may therefore differ in thickness and velocity structure from normal oceanic crust.
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  • 61
    Publication Date: 2021-01-21
    Description: Seismic full waveform inversion (FWI) is a powerful method for estimating quantitative subsurface physical parameters from seismic data. As the full waveform inversion is a non-linear problem, the linearized approach updates model iteratively from an initial model, which can get trapped in local minima. In the presence of a high velocity contrast, such as at Moho, the reflection coefficient and recorded waveforms from wide-aperture seismic acquisition are extremely non-linear around critical angles. The problem at the Moho is further complicated by the interference of lower crustal (Pg) and upper mantle (Pn) turning ray arrivals with the critically reflected Moho arrivals (PmP). In order to determine velocity structure near Moho, a non-linear method should be used. We propose to solve this strong non-linear FWI problem at Moho using a trans-dimensional Markov chain Monte Carlo (MCMC) method, where the earth model between lower crust and upper mantle is idealy parameterized with a 1-D assumption using a variable number of velocity interfaces. Different from common MCMC methods that require determining the number of unknown as a fixed prior before inversion, trans-dimensional MCMC allows the flexibility for an automatic estimation of both the model complexity (e.g. the number of velocity interfaces) and the velocity-depth structure from the data. We first test the algorithm on synthetic data using four representative Moho models and then apply to an ocean bottom seismometer (OBS) data from the Mid-Atlantic Ocean. A 2-D finite-difference solution of an acoustic wave equation is used for data simulation at each iteration of MCMC search, for taking into account the lateral heterogeneities in the upper crust, which is constrained from travel time tomography and is kept unchanged during inversion; the 1-D model parameterization near Moho enables an efficient search of the trans-dimensional model space. Inversion results indicate that, with very little prior and the wide-aperture seismograms, the trans-dimensional FWI method is able to infer the posterior distribution of both the number of velocity interfaces and the velocity-depth model for a strong nonlinear problem, making the inversion a complete data-driven process. The distribution of interface matches the velocity discontinuities. We find that the Moho in the study area is a transition zone of 0.7 km, or a sharp boundary with velocities from around 7 km/s in the lower crust to 8 km/s of the upper mantle; both provide nearly identical waveform match for the field data. The ambiguity comes from the resolution limit of the band-limited seismic data and limited offset range for PmP arrivals.
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  • 62
    Publication Date: 2021-01-21
    Description: Gully formation has been associated to groundwater seepage in unconsolidated sand- to gravel-sizedsediments. Our understanding of gully evolution by groundwater seepage mostly relies on experiments and nu-merical simulations, and these rarely take into consideration contrasts in lithology and permeability. In addition,process-based observations and detailed instrumental analyses are rare. As a result, we have a poor understandingof the temporal scale of gully formation by groundwater seepage and the influence of geological heterogeneityon their formation. This is particularly the case for coastal gullies, where the role of groundwater in their for-mation and evolution has rarely been assessed. We address these knowledge gaps along the Canterbury coastof the South Island (New Zealand) by integrating field observations, luminescence dating, multi-temporal un-occupied aerial vehicle and satellite data, time domain electromagnetic data and slope stability modelling. Weshow that gully formation is a key process shaping the sandy gravel cliffs of the Canterbury coastline. It is anepisodic process associated to groundwater flow that occurs once every 227 d on average, when rainfall intensi-ties exceed 40 mm d−1. The majority of the gullies in a study area southeast (SE) of Ashburton have undergoneerosion, predominantly by elongation, during the last 11 years, with the most recent episode occurring 3 yearsago. Gullies longer than 200 m are relict features formed by higher groundwater flow and surface erosion〉2 kaago. Gullies can form at rates of up to 30 m d−1via two processes, namely the formation of alcoves and tunnelsby groundwater seepage, followed by retrogressive slope failure due to undermining and a decrease in shearstrength driven by excess pore pressure development. The location of gullies is determined by the occurrenceof hydraulically conductive zones, such as relict braided river channels and possibly tunnels, and of sand lensesexposed across sandy gravel cliffs. We also show that the gully planform shape is generally geometrically similarat consecutive stages of evolution. These outcomes will facilitate the reconstruction and prediction of a prevalenterosive process and overlooked geohazard along the Canterbury coastline.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
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  • 63
    Publication Date: 2021-01-20
    Description: In a conserved culture of the purple sulfur bacterium Thiospirillum jenense DSM216T, cells of this species were easily recognized by cell morphology, large-size spirilla and visible flagellar tuft. The Tsp. jenense genome is 3.22 Mb in size and has a GC content of 48.7 mol%. It was readily identified as a member of the Chromatiaceae by the complement of proteins in its genome. A whole genome comparison clearly placed Tsp. jenense near Thiorhodovibrio and Rhabdochromatium species and somewhat more distant from Thiohalocapsa and Halochromatium species. This relationship was also found with the sequences of the photosynthetic reaction center protein PufM. The genome sequence supported important properties of this bacterium: the presence of ribulose-bisphosphate carboxylase and enzymes of the Calvin cycle of autotrophic carbon dioxide fixation but the absence of carboxysomes, an incomplete tricarboxylic acid cycle and the lack of malate dehydrogenase, the presence of a sulfur oxidation pathway including adenylylsulfate reductase (aprAB) but absence of assimilatory sulfate reduction, the presence of hydrogenase (hoxHMFYUFE), nitrogenase and a photosynthetic gene cluster (pufBALMC). The FixNOP type of cytochrome oxidase was notably lacking, which may be the reason that renders the cells highly sensitive to oxygen. Two minor phototrophic contaminants were found using metagenomic binning: one was identified as a strain of Rhodopseudomonas palustris and the second one has an average nucleotide identity of 82% to the nearest neighbor Rhodoferax antarcticus. It should be considered as a new species of this genus and Rhodoferax jenense is proposed as the name.
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  • 64
    Publication Date: 2021-01-20
    Description: The Arctic Ocean is subject to severe environmental changes, including the massive decline in sea ice due to continuous warming in many regions. Along with these changes, the Arctic Ocean’s ecosystem is affected on various scales. The pelagic microbial food web of the Arctic is of particular interest, because it determines mass transfer to higher trophic levels. In this regard, variations in the size structure of the microbial community reflect changes in size-dependent bottom-up and top-down processes. Here we present analyses of microscopic data that resolve details on composition and cell size of unicellular plankton, based on samples collected between 2016 and 2018 in the Fram Strait. Using the Kernel Density Estimation method, we derived continuous size spectra (from 1 μm to ≈ 200 μm Equivalent Spherical Diameter, ESD) of cell abundance and biovolume. Specific size intervals (3–4, 8–10, 25–40, and 70–100μm ESD) indicate size-selective predation as well as omnivory. In-between size ranges include loopholes with elevated cell abundance. By considering remote sensing data we could discriminate between polar Arctic- and Atlantic water within the Fram Strait and could relate our size spectra to the seasonal change in chlorophyll-a concentration. Our size spectra disclose the decline in total biovolume from summer to autumn. In October the phytoplankton biovolume size-spectra reveal a clear relative shift towards larger cell sizes (〉 30 μm). Our analysis highlights details in size spectra that may help refining allometric relationships and predator-prey dependencies for size-based plankton ecosystem model applications.
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  • 65
    Publication Date: 2021-01-20
    Description: SO277 OMAX served two scientific projects. The objectives of the first project, SMART, were to develop multi-disciplinary methodologies to detect, quantify, and model offshore groundwater reservoirs in regions dominated by carbonate geology such as the Mediterranean Sea. To this end we acquired controlled-source electromagnetic, seismic, hydroacoustic, geochemical, seafloor imagery data off Malta. Preliminary evaluation of the geophysical data show that there are resisitivity anomalies that may represent offshore freshwater aquifers. The absence of evidence for offshore springs means that these aquifers would be confined and that it will be difficult to use them in a sustainable manner. The objective of the second project, MAPACT-ETNA, is to monitor the flank of Etna volcano on Sicily which is slowly deforming seaward. Here, we deployed six seafloor geodesy stations and six ocean bottom seismometers for long-term observation (1-3 years). In addition, we mapped the seafloor off Mt. Etna and off the island of Stromboli to constrain the geological processes that control volcanic flank stability.
    Type: Report , NonPeerReviewed
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  • 66
    Publication Date: 2021-01-20
    Description: Serum calcium (Ca), bone biomarkers and radiological imaging do not allow accurate evaluation of bone mineral balance (BMB), a key determinant of bone mineral density (BMD) and fracture risk. We studied naturally occurring stable (non‐radioactive) Ca isotopes in different body pools as a potential biomarker of BMB. 42Ca and 44Ca are absorbed from our diet and sequestered into different body compartments following kinetic principles of isotope fractionation; isotopically light 42Ca is preferentially incorporated into bone, whereas heavier 44Ca preferentially remains in blood and is excreted in urine and feces. Their ratio (δ44/42Ca) in serum and urine increases during bone formation and decreases with bone resorption. In 117 healthy participants we measured Ca isotopes, biomarkers, and BMD by DXA and tibial peripheral quantitative CT (pQCT). 44Ca and 42Ca were measured by multi‐collector ionization‐coupled plasma mass‐spectrometry in serum, urine and feces. The relationship between bone Ca gain and loss was calculated using a compartment model. δ44/42Caserum and δ44/42Caurine were higher in children (n=66, median age 13 years) compared to adults (n=51, median age 28 years; p〈0.0001 and p=0.008 respectively). δ44/42Caserum increased with height in boys (p〈0.001, R2=0.65) and was greatest at Tanner stage 4. δ44/42Caserum correlated positively with biomarkers of bone formation (25‐hydroxyvitaminD [p〈0.0001, R2=0.37] and alkaline phosphatase [p=0.009, R2=0.18]) and negatively with bone resorption marker PTH (p=0.03, R2=0.13). δ44/42Caserum strongly positively correlated with tibial cortical BMD‐Z‐score (n=62; p〈0.001, R2=0.39), but not DXA. Independent predictors of tibial cortical BMD‐Z‐score were δ44/42Caserum (p=0.004, β=0.37), 25‐hydroxyvitaminD (p=0.04, β=0.19) and PTH (p=0.03, β=‐0.13), together predicting 76% of variability. In conclusion, naturally occurring Ca isotope ratios in different body compartments may provide a novel, non‐invasive method of assessing bone mineralization. Defining an accurate biomarker of BMB could form the basis of future studies investigating Ca dynamics in disease states and the impact of treatments that affect bone homeostasis.
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  • 67
    Publication Date: 2021-01-19
    Description: We present porosity and free gas estimations and their uncertainties at anactive methane venting site in the UK sector of the North Sea. In the Scan-ner Pockmark area in about 150m water depth, we performed a multi-disciplinary experiment to investigate the physical properties of fluid flowstructures within unconsolidated glaciomarine sediments. Here we focus onthe towed controlled source electromagnetic (CSEM) data analysis with con-straints from seismic reflection and core logging data. Inferred backgroundresistivity values vary between 0.6–1 Ωm at the surface and 1.9–2.4 Ωm at150 mbsf. We calibrate Archie’s parameters with measurements on cores, andestimate porosities of about 50±10% at the seafloor decreasing to 25±3% at 150 mbsf which matches variations expected for mechanical compaction ofclay rich sediments. High reflectivity in seismic reflection data is consistentwith the existence of a gas pocket. A synthetic study of varying gas contentin this gas pocket shows that at least 33±8% of free gas are required to causea distinct CSEM data anomaly. Real data inversions with seismic constraintssupport the presence of up to 34±14% free gas in a 30–40 m thick gas pocketunderneath the pockmark within the stratigraphic highs of a till layer abovethe glacial unconformity in the Aberdeen Ground Formation.
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  • 68
    Publication Date: 2021-01-19
    Description: Evaluation of seismic reflection data has identified the presence of fluid escape structures cross-cutting overburden stratigraphy within sedimentary basins globally. Seismically-imaged chimneys/pipes are considered to be possible pathways for fluid flow, which may hydraulically connect deeper strata to the seabed. These fluid migration pathways through the overburden must be constrained to enable secure, long-term subsurface carbon dioxide (CO2) storage. We have investigated a site of natural active fluid escape in the North Sea, the Scanner Pockmark Complex, to determine the physical characteristics of focused fluid conduits, and how they control fluid flow. Here we show that a multi-scale, multi disciplinary experimental approach is required for complete characterisation of fluid escape structures. Geophysical techniques are necessary to resolve fracture geometry and subsurface structure (e.g., multifrequency seismics) and physical parameters of sediments (e.g., controlled source electromagnetics) across length scales (m to km). At smaller (mm to cm) scales, sediment cores were sampled directly and their physical and chemical properties assessed using laboratory-based methods. Numerical modelling approaches bridge the resolution gap, though their validity is dependent on calibration and constraint from field and laboratory experimental data. Further, time-lapse seismic and acoustic methods capable of resolving temporal changes are key for determining fluid flux. Future optimisation of experiment resource use may be facilitated by the installation of permanent seabed infrastructure, and replacement of manual data processing with automated workflows. This study can be used to inform measurement, monitoring and verification workflows that will assist policymaking, regulation, and best practice for CO2 subsurface storage operations.
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