ALBERT

Description: Sediment-Hosted Geothermal Systems (SHGSs) are hybrid geological systems, where volcanic and sedimentary domains interact, leading to mixtures of inorganic and organic gases. Typically characterized by geothermal (thermometamorphic or mantle-derived) CO2 and biotic (microbial or thermogenic) CH4, SHGSs occur in sedimentary basins crossed by magmatic intrusions or involved in volcanic plumbing systems. These systems can be of considerable interest for petroleum exploration and natural greenhouse-gas emission studies, but systematic studies for their characterization and worldwide distribution are missing. Here, we provide a review of SHGSs identified so far, and propose methodological criteria for their definition and identification, based on integrated geological and gas-geochemical parameters. We find that SHGSs are typically characterized by: (a) fluids dominated by mantle or decarbonation-methamorphic CO2 (〉50 vol%); (b) considerable amounts of CH4 and heavier hydrocarbons (at least 1.5 vol%, generally up to 30–40 vol%), produced by microbial or thermogenic degradation of organic matter hosted in sedimentary rocks; (c) tectonically active sedimentary basins (back-arc, rift zones and foredeep), generally hosting petroleum fields and within ~300 km from recent or ancient volcanic centers. This analysis resulted in a global map including a first set of 33 SHGSs located in North America, Central and Eastern Europe, Far East, Eastern Oceania and Northern New Zealand, and a second set of potential SHGS prone areas, occurring also in South America, North Africa, Middle East and Kamchatka. The present SHGS map can evolve on the basis of more detailed geological analysis and new gas-geochemical data.

Description: Pathogenic bacteria use Quorum sensing (QS) to regulate the expression of virulence factors involved in plant tissue infection. Some of these factors are the production of biofilm, hydrolytic enzymes, toxins, and plasmids; therefore, the interruption of this system could be a useful tool to control plant tissue infections. This review analyzes the potential treatments to interrupt QS and control the infection of plant tissues.

Description: Large Magnitude (6–8) Late Quaternary Japanese volcanic eruptions are responsible for widespread ash (tephra) dispersals providing key isochrons suitable for the synchronisation and dating of palaeoclimate archives across East Asia, the NW Pacific and beyond. The transfer of geochronological information using these eruption deposits demands robust tephra correlations underpinned by detailed and precise volcanic glass geochemical data. Presented here is a major (electron microprobe; EMP) and trace element (Laser ablation inductively coupled plasma mass spectrometry; LA-ICP-MS) characterisation of near-source deposits from a series of large magnitude Japanese eruptions spanning approximately the last 150 ka. These data offer new insights into diagnostic compositional variations of the investigated volcanic sources spanning the Japanese islands. Whilst in the case of the highly productive Aso caldera (Kyushu), we are able to explore compositional variations through successive large magnitude eruptions (50–135 ka). These near-source volcanic glass data are used to validate and refine the visible tephrostratigraphy of the intensely dated Lake Suigetsu sedimentary record (SG06 core), Honshu Island, whilst also illustrating key tephrostratigraphic tie points to other East Asian palaeoclimate records (e.g. Lake Biwa). The identification of widespread Japanese tephrostratigraphic markers in the SG06 sediment record enables us to place chronological constraints on these ash dispersals, and consequently explosive volcanism at source volcanoes situated along the Kyushu Arc, including Kikai, Ata and Aso calderas. The proximal Aso-4 Ignimbrite (Magnitude 7.7) deposit is dated here by 40Ar/39Ar at 86.4 ± 1.1 ka (2σ), and provides a chronological anchor (SG06-4963) for the older sediments of the Lake Suigetsu record. Finally, trace element glass data verify visible ash fall layers derived from other compositionally distinct source regions of Japanese volcanism, including activity along the northern Izu-Bonin arc and North East Japan Arcs. These findings underline the Lake Suigetsu record as central node in the Japanese tephrostratigraphic framework. Highlights • Near-source and distal (Lake Suigetsu) characterisation of Late Quaternary widespread Japanese Tephrostratigraphic markers. • Grain-specific major and trace element volcanic glass analyses (EMP & LA-ICP-MS). • Chemical discrimination of Japanese volcanic source regions for the purposes of Tephrochronology. • Unlocking the Lake Suigetsu (SG06 core) visible tephra layers for reliable archive synchronisation. • Proximal 40Ar/39Ar age of 86.4 ± 1.1 ka (2σ) for the Magnitude 7.7 caldera forming Aso-4 eruption.

Description: The Late Devonian (383-359 Ma) was a time of prolonged climate instability with catastrophic perturbation of global marine ecosystems at the Frasnian-Famennian (F-F) and the Devonian-Carboniferous (D-C) boundaries. The causes and mechanisms of anoxia and extinction at the F-F interval are not clearly delineated, and alternative explanations for virtually every aspect of this interval are still intensely debated. In many (but not all) locations, the F-F interval is characterized by two dark, organic-rich lithologies: the Lower and Upper Kellwasser beds (as originally described in Germany) that represent a stepwise ocean anoxia and extinction sequence. The Upper and Lower Kellwasser anoxia event beds are often collectively termed the Kellwasser Event, and the termination of this sequence is within the Upper Kellwasser Event at the F-F boundary. Current knowledge is limited by significant sampling bias, as most previous studies sampled epicontinental seaways or passive continental shelves, primarily from localities across Europe and North America. Together these formed a single equatorial continent with a rising mountain chain during the Late Devonian. Our understanding of the Kellwasser Event is thus based on data and observations from a restricted set of paleoenvironments that may not represent the complete range of Late Devonian environments and oceanic conditions. In the last decade, new methodologies and research in additional paleoenvironments around the world confirm that the Kellwasser Event was global in scope, but also that its expression varies with both paleoenvironment and paleogeography. Studying the many differing geochemical and lithological expressions of the Kellwasser Event using a) a wide variety of paleoenvironments, b) a multiproxy approach, and c) placement of results into the broader context of Late Devonian marine biodiversity patterns is vital for understanding the true scope of ocean anoxia, and determining the causes of the marine biodiversity crisis at the F-F boundary. Highlights • Bias in existing samples limits understanding of the Frasnian-Famennian biodiversity crisis and the Kellwasser anoxia event. • The Kellwasser Event was global but its expression is highly dependent on paleoenvironment and paleogeography. • The Kellwasser Event was due to "top-down" climate forcing with surface eutrophication not upwelling anoxic bottom water. • The F-F crisis was a lack of species origination in environments with climate stress and changes in sediment/nutrient supply.

Description: Northeast Atlantic marine ecosystems such as the Bay of Biscay, Celtic Sea, English Channel, Subpolar Gyre region, Icelandic waters and North Sea as well as the Mediterranean Sea show concomitant ‘regime shift’-like changes around the mid-1990s, which involved all biota of the pelagial: phytoplankton, zooplankton, pelagic fish assemblages, demersal fish assemblages and top predators. These shifts were caused by complex ocean-atmosphere interactions initiating large-scale changes in the strength and direction of the current systems, that move water masses around the North Atlantic, and involved the North Atlantic Oscillation (NAO), the Atlantic Meridional Overturning Circulation (AMOC), and the subpolar gyre (SPG). The contractions and expansions of the SPG and fluctuations of the Atlantic Multidecadal Oscillation (AMO) play a key role in these complex processes. Small pelagic fish population trends were the sentinels of these changes in the mid-1990s in the ecosystems under investigation.

Description: Atlantic cod (Gadus morhua) is an important recreational and commercial fisheries target species in the Northern hemisphere. Release rates are high in the recreational fishery due to regulatory and voluntary catch-and-release practice. Although post-release mortality of cod is relatively low, there is potential for further reductions. The most effective way to reduce post-release mortality is to minimize the catch of sublegal fish or non-target species and to reduce hooking injuries by using more selective fishing methods. This study investigated the influence of the lure/bait type on: (1) size of fish, (2) catch and harvest, (3) proportion of bycatch, (4) hooking location, and (5) injury (bleeding) in the western Baltic Sea recreational cod fishery. Data were collected via random onboard sampling of 35 charter vessel angling trips (778 anglers) and during two supplementary studies in the western Baltic Sea. Overall, the median total length was significantly higher for cod caught on artificial lures (39 cm) than for cod caught on natural bait (28 cm), leading to a 43% higher proportion of sublegal (〈38 cm) cod for bait than for lure. Median catch-per-unit-efforts (number of captured cod per angling hour) did not differ significantly between lure and bait angling (both: 0.49 cod per hour), whereas the median harvest-per-unit-effort (number of captured cod ≥ minimum landing size (38 cm) per angling hour) was significantly higher for lure (0.24 cod ≥38 cm per hour) than for bait angling (0.06 cod ≥38 cm per hour). The incidence of deep hooking and severe bleeding was significantly higher for bait angling. Furthermore, bait angling significantly increased bycatch of other species dominated by whiting (Merlangius merlangus) and European flounder (Platichthys flesus). Cod anglers can reduce the catch of sublegal cod and non-target species and minimize hooking injuries of released fish by using lures instead of bait in the western Baltic Sea. Thus, voluntary terminal gear recommendations may be an effective tool for anglers and managers to increase selectivity in recreational cod fisheries.

Description: Highlights • Frequent sediment resuspension may have buffered D-Fe released from shelf sediments. • 228Ra was used to estimate trace element fluxes from the Chukchi shelf sediments. • The estimated sediment 228Ra flux ranks among the highest reported globally. • About 10–25% of the Chukchi shelf sediment Fe flux is exported to the Arctic Ocean. The Chukchi Sea is a primary site for shelf-ocean exchange in the Arctic region and modifies Pacific-sourced water masses as they transit via the Bering Strait into the Arctic Ocean. The aim of this study was to use radium and trace metal distributions to improve our understanding of biogeochemical cycles in the Bering and Chukchi Seas, and evaluate their potential response to future changes in the Arctic. We investigated the distributions of dissolved and total dissolvable trace metals (Cd, Fe, Ni, Cu, Zn, Mn, Co, and Pb) in the Bering and Chukchi Seas during spring. In addition, the long-lived radium isotopes (226Ra and 228Ra) were measured as tracers of benthic trace metal inputs. Trace metal concentrations, especially Fe and Mn, were highly elevated in Chukchi shelf waters compared with the open Arctic Ocean and Bering Strait. Trace metal, nutrient, and Ra patterns suggested that Fe, Mn, and Co concentrations were predominantly controlled by reductive benthic inputs, whereas the other trace metals were influenced by biological uptake and release processes. We propose that Fe, Mn, and Co in the Chukchi Sea are supplied from shelf sediments during winter overturning, and we combine the 228Ra fluxes with the distributions of Fe, Mn, and Co to provide a first estimate of their benthic fluxes in the region. The average benthic flux of 228Ra was 1.49 × 108 atoms m−2 d−1, which is among the highest rates reported globally. Estimated dissolved Fe (D-Fe) flux from the sediments was 2.5 μmol m−2 d−1, whereas D-Mn and D-Co fluxes were 8.0 μmol m−2 d−1 and 0.2 μmol m−2 d−1, respectively. The off-shelf transport of D-Fe to the Arctic Ocean is estimated to be about 10–25% of the benthic Fe flux, with the remainder retained on the shelf due to scavenging and/or phytoplankton uptake. Our results highlight the importance of the Chukchi Sea as a major source of the micro-nutrients to the Arctic Ocean, thereby supporting primary production. Long-term changes in factors that affect cross-shelf mixing, such as the observed reduction in ice cover, may therefore enhance shelf nutrient inputs and primary productivity in the Arctic.

Description: Proglacial streams deliver melt water and chemical weathering products, including nutrients and radiogenic isotopes, from continental ice sheets to the ocean. Weathering products are also delivered to the ocean in non-glacial streams that form following ice sheet retreat and are disconnected from ice sheet meltwater by hydrologic divides. If weathering reactions differ in non-glacial and proglacial stream catchments, the streams could deliver different types and magnitudes of solutes to the ocean, depending on relative discharge volumes. Unlike proglacial streams, however, little is known of non-glacial stream solute compositions or discharge. Here we show specific discharges are similar from a proglacial stream draining the Greenland Ice Sheet (GrIS) with several streams disconnected from the ice sheet. We also evaluate weathering reactions across a 170-km transect in western Greenland that contains one proglacial stream draining the GrIS, and two coastal (ice distal) and three inland (ice proximal) areas with non-glacial streams. Non-glacial streams exhibit solute compositions and offsets between dissolved and bedload Sr isotope ratios that indicate weathering increases toward the coast with exposure age and precipitation. Major element mass balance calculations show weathering reactions shift from predominately carbonic acid weathering of carbonate minerals inland near the ice sheet to predominately sulfuric acid weathering of carbonate minerals near the coast. Strontium concentrations and isotopic ratios of the proglacial stream reflect mixing of at least two subglacial sources and minor in-stream weathering that consumes CO2. About 5 times less CO2 is consumed per liter in the proglacial than inland non-glacial streams; however, arid conditions inland suggest limited discharge from the ungauged inland streams leads to less total CO2 weathering than proglacial stream. One coastal area consumes less CO2 per liter than the proglacial stream and another coastal area exhibits net CO2 production. These results indicate estimates for glacial foreland solute fluxes and CO2 weathering consumption and production should include estimates from both non-glacial and proglacial streams. Understanding weathering fluxes from these two types of streams will be important for evaluations of past ice sheet retreat and predictions of future solute and CO2 fluxes associated with continued ice sheet retreat.

Description: The Earth’s ocean floor deforms continuously under the influence of plate tectonic processes. In recent years, the development of deep-sea instruments using acoustic direct-path ranging allows observations of ocean floor deformation with unprecedented spatial and temporal resolution. Due to rapid technological progress, acoustic ranging emerged as a central research field to monitor seafloor deformation. Here we review recent developments and the progress of direct-path ranging applications. We discuss the methodology and examine the effects of the oceanographic environment on the measurement precision. Comparing the resolution of previous deployments, we find that the baseline uncertainty increases linearly with baseline length, at least for distances up to 3 km, but with different linear relations for each deployment. Measurements of displacement at millimeter-level precision across normal, thrust or strike-slip faults are discussed to evaluate the influence of dedicated network designs appropriate for the discrete fault geometries. Furthermore, tectonically quiet areas, such as flanks of coastal or ocean island volcanoes and passive continental margins pose substantial hazards that often lack in-situ monitoring and are therefore a significant target for the application of seafloor geodetic techniques.

Description: The role of accessory minerals in the incongruent release of Hf and Pb during continental weathering and its implications for the generation of distinct seawater isotope compositions is subject of debate. While it has been suggested that radiogenic Hf and Pb isotope signatures released during the dissolution of rocks are controlled by the relative abundances of minerals with distinct isotope compositions and differences in their resistance to dissolution there has not been a comprehensive experimental investigation of these processes to date. We carried out systematic sequential leaching experiments on fresh and partly weathered granitic rock samples as well as separated zircons from the Central Aar Granite in Switzerland. Combined with major and rare earth element concentrations our new quantitative experimental data reveal systematic preferential release of radiogenic Nd, Hf and Pb isotopes primarily controlled by dissolution characteristics of the host rock's easily dissolvable accessory and major minerals, in particular apatite and sphene, during weak chemical weathering. Moreover, Pb isotope signatures of incipient weathering conditions, contrary to expectations, indicate initial congruent release of Pb from freshly exposed mineral surfaces that becomes subsequently incongruent. During more advanced chemical weathering stages, as well as enhanced physical weathering conditions, the dissolution of major minerals (i.e. feldspars) becomes dominant for Nd and Pb isotope signatures, whereas Hf isotopes are still dominated by contributions from highly radiogenic accessories. Additional leaching experiments of zircon separates were performed to test the specific role of zircons for Hf isotope compositions of riverine runoff. It is demonstrated that zircon is more efficiently dissolved when physical weathering is enhanced. This increased Hf release originating from partial dissolution of zircons, however, is quantitatively not sufficient to explain less radiogenic Hf isotope signatures in seawater during episodes of enhanced mechanical erosion alone. Moreover, the observed addition of Hf from the more congruent dissolution of the zircon-free fractions of the parent rock due to enhanced physical weathering indicate that these minerals also play an important role in controlling Hf isotope signatures released under deglacial conditions.

Description: The Manihiki Plateau, a Large Igneous Province (LIP) in the western Pacific, has been proposed to be emplaced as part of the “Greater Ontong Java Event” during the early Cretaceous. Shortly after its formation, the Manihiki Plateau fragmented into multiple sub-provinces. Plate tectonic reconstructions ignore this fragmentation, treating the Manihiki Plateau as a single crustal block. By analyzing two seismic refraction/wide-angle reflection profiles crossing the two largest sub-provinces of the Manihiki Plateau, we provide new insight into their deep crustal structure and magmatic evolution. Our data indicate that the High Plateau and the Western Plateaus were emplaced as a single unit during an initial phase of massive magmatic activity, but later magmatic stages altered the individual sub-provinces considerably. The High Plateau has a crustal thickness of 20 km and its P-wave velocity distribution is comparable to previously surveyed oceanic LIPs. Strong secondary magmatic phases are visible by eruptive centers and former magmatic pathways in the middle and lower crust. The Western Plateaus, which have a crustal thickness decreasing gradually from 17.3 km (East) to 9.2 km (West), experienced smaller amounts of magmatism mainly along fault zones and on local seamounts. Therefore, we propose a distinct development of the two main sub-provinces of the Manihiki Plateau after their initial joint emplacement. The High Plateau experienced voluminous multi-phase magmatic accretion and extrusion, whereas the thinner Western Plateaus exhibit only relatively minor magmatic growth. Such a large difference in the evolution process has not been reported from any other oceanic LIP so far.

Description: A central aspect of coastal biogeochemistry is to determine how nutrients, lithogenic- and organic matter are distributed and transformed within coastal and estuarine environments. Analyses of the spatio-temporal changes of total suspended matter (TSM) concentration indicate strong and variable linkages between intertidal fringes and pelagic regions. In particular, knowledge about the organic fraction of TSM provides insight to how biogenic and lithogenic particulate matter are distributed in suspension. In our study we take advantage of a set of over 3000 in situ Loss on Ignition (LoI) data from the Southern North Sea that represent fractions of particulate organic matter (POM) relative to TSM (LoI $\equiv$ POM:TSM). We introduce a parameterization (POM-TSM model) that distinguishes between two POM fractions incorporated in TSM. One fraction is described in association with mineral particles. The other represents a seasonally varying fresh pool of POM. The performance of the POM-TSM model is tested against data derived from MERIS/ENVISAT-TSM products of the German Bight. Our analysis of remote sensing data exhibits specific qualitative features of TSM that can be attributed to distinct coastal zones. Most interestingly, a transition zone between the Wadden Sea and seasonally stratified regions of the Southern North Sea is identified where mineral associated POM appears in concentrations comparable to those of freshly produced POM. We will discuss how this transition is indicative for a zone of effective particle interaction and sedimentation.The dimension of this transition zone varies between seasons and with location. Our proposed POM-TSM model is generic and can be calibrated against in situ data of other coastal regions.

Description: Highlights: • Clay dehydration water expelled from buried sediments drives mud volcanism. • Rise of fluids mediated by crustal-scale strike-slip faults cross-cutting wedge. • On active accretionary wedge, petroleum accumulations were dismantled in Neogene. • 4He enrichment and δ13C-CH4 ~−50‰ in fluids reflect an open hydrocarbon system. • Petroleum pools remain on shallow margin. Microbial gas vented out of active wedge. Abstract: A geochemical study of the composition of hydrocarbon gases and helium isotopes (3He/4He) in fluids from Mud Volcanoes (MVs) located on and out of the active accretionary wedge of the Gulf of Cadiz (GoC) provides information on fluid sources and migrations in deeply buried sediments. The GoC is a tectonically active segment of the Africa-Iberia plate boundary occluded beneath the thick sediments of an accretionary wedge dissected by crustal-scale strike-slip faults. Initially built during the Miocene Gibraltar Arc subduction, the wedge has since developed toward the W-NW in an oblique convergent setting. Interstitial water expelled from clays undergoing diagenesis in buried sediments drives mud volcanism on the wedge, with MVs located along strike-slip faults mediating fluid ascent. The large excess of radiogenic helium (4He) in all GoC fluids agrees with a clay mineral dehydration source of water. Hydrocarbon gases from all deepwater MVs bear methane having similar stable carbon isotope compositions of ~−50‰VPDB whether fluids are highly enriched in methane relative to heavier homologues (C2+) or not (Methane / (Ethane + Propane) ~10 to 10,000). We suggest that methane with −50‰VPDB was largely diffused out of early generating source rocks, and became dissolved in the water expelled by the buried sediments. Consistently, low 3He/4He ratios suggest an open hydrocarbon system: Petroleum accumulations and 3He dissolved in the original sedimentary pore water have mostly escaped into the water column during the major Late Neogene compressional events. At present, some MVs vent CH4-rich fluids from dewatering sediments, while other structures located on active thrusts additionally vent C2+-rich gases generated by active Cretaceous source intervals. By contrast, evaporitic seals preserved petroleum accumulations on the shallow Moroccan Margin, while the westernmost MVs located out of the accretionary wedge vent microbial gas.

Description: Abstract ETHNOPHARMACOLOGICAL RELEVANCE: The oleoresin of Brazilian Copaifera reticulata is a traditional remedy used for the treatment of skin and urinary tract infections, respiratory diseases, rheumatism, ulcer and tumours; thus, playing an important role in the primary health care of the indigenous population. AIM: As most previous pharmacological tests used the crude oleoresin and only a few studies so far dealt with enriched fractions or pure chemically defined compounds, the aim of this study was to systematically evaluate the antimicrobial and cytotoxic properties of the Copaifera reticulata oleoresin and to assign traditional uses to specific secondary metabolites. MATERIALS AND METHODS: The oleoresin, as well as its neutral and acidic fractions were tested for their activity against six cancer cell lines, two clinically relevant bacterial strains, and two dermatophytes. Both fractions were analysed by GC-MS and UHPLC-ELSD, respectively. The antibacterial acidic phase was further fractionated by preparative chromatography to purify and characterize the compounds responsible for the observed pharmacological effect. RESULTS: Whereas no cytotoxic activity was detected, the crude oleoresin and its acidic fraction showed antibacterial activity against gram-positive bacteria Enterococcus faecium (IC50 values 4.2 and 4.8 µg/mL, respectively) and methicillin-resistant Staphylococcus aureus (MRSA, IC50 values 5.3 and 7.2 µg/mL, respectively). Purification of the acidic fraction of the C. reticulata oleoresin yielded two dicarboxylic diterpene acids and the four main diterpene acids, comprising three different diterpene scaffolds. Interestingly, the activity was not restricted to a particular diterpene-type but rather depended on the compounds' lipophilicity, with the most active constituent showing IC50 values of 1.6 (E. faecium) and 2.5 µg/mL (MRSA), respectively. Furthermore, ent-polyalthic acid, the major diterpenoid, was significantly active against dermatophytes with IC50 values of 6.8 µg/mL (Trichophyton rubrum) and 4.3 µg/mL against (T. mentagrophytes). CONCLUSION: The present study proved the antimicrobial effects of the C. reticulata oleoresin and its diterpenoid constituents, confirming its wide use in folk medicine for the treatment of skin and urinary tract infections. The inhibitory activity of copaiba diterpenoids against dermatophytic fungi as well as the gram-positive bacteria E. faecium and MRSA is being reported for the first time, providing potential lead structures for the treatment of these clinically relevant bacterial strains.

Description: Rapid anthropogenic climate change is a major threat to ocean biodiversity, increasing the challenge for marine conservation. Strategic conservation planning, and more recently marine spatial planning (MSP) are among the most promising management tools to operationalize and enforce marine conservation. As yet, climate change is seldom incorporated into these plans, potentially curtailing the effectiveness of designated conservation areas under novel environmental conditions. Reliable assessment of current and future climate change threats requires the ability to map climate-driven eco-evolutionary changes and the identification of vulnerable and resistant populations. Here we explore the heretofore largely unrecognized value of information gained from physiological, ecological and evolutionary studies to MSP under ongoing climate change. For example, we explore how climate threats do not necessarily follow latitudinal gradients, such that both risk hotspots and refugia occur in mosaic distributions along species ranges - patterns that may be undetectable without knowledge of biological vulnerabilities at regional and local scales. Because co-occurring species can exhibit markedly different vulnerabilities to the same environmental changes, making ecological predictions requires, when possible, measuring the fundamental niches of key species (e.g., with the use of thermotolerance experiments). Forecasting also requires development of tools to identify the likelihood of community-level thresholds or tipping points (e.g., with the use of near-real world mesocosms), and assessment of the potential of populations for adaptation (e.g., with common garden experiments). Such research will facilitate better predictive models for the fate of populations, species, ecosystems and their functions. Ultimately, unfolding the complexity of the processes underlying climate change impacts will facilitate quantifying and reducing uncertainty in spatial planning decision processes and will enable the development of practical tools to validate adaptive conservation strategies.

Description: Highlights • First deep water Nd and Pb isotope records from the glacial–deglacial Nordic Seas. • Deglacial changed by up to six units from unradiogenic LGM background. • Glacial–deglacial Nd and Pb isotope changes controlled by local weathering input. • Pb isotopes suggest synchronous postglacial weathering fluxes around the North Atlantic. • Holocene Nd isotope evolution dominated by re-invigorated water mass mixing. Abstract Neodymium (Nd) isotopes are a powerful proxy tool for reconstructing past changes in water mass mixing, but reliable application of this proxy requires constraints on past changes of source water compositions. A key region of the global deep water circulation system are the Nordic Seas, which provide dense waters fundamental for the formation of North Atlantic Deep Water (NADW). Yet, the Nd isotope evolution of past deep waters in the Nordic Seas is so far poorly constrained. Here we present the first reconstructions of seawater Nd isotope compositions extracted from marine sediments at two locations in the central and northern Nordic Seas covering the period from the last glacial to the present. Further insights into past changes in sediment provenance, weathering inputs and water mass mixing are provided by complementary seawater and detrital strontium (Sr) and lead (Pb) isotope compositions. Our new data reveal that changes in source and magnitude of weathering inputs from the Scandinavian and Svalbard–Barents Ice Sheets (SIS and SBIS, respectively) controlled the Nd and Pb isotope composition of the Nordic Seas' deep waters during the last glacial period. During the Last Glacial Maximum (LGM), deep waters showed distinctly unradiogenic Nd and radiogenic Pb isotope signatures most likely driven by weathering inputs of the SBIS. In contrast, the deglaciation was characterized by enhanced SBIS ice dynamics and/or meltwater release delivering sediments from the distal Eurasian shelves to the Norwegian Sea. Pulses of volcanogenic sediment supply changed the deep water Nd isotope composition during Heinrich Stadials 1, 2 and the Bølling period. As such, the glacial–deglacial Nd and Pb isotope evolution was markedly different in the Nordic Seas, the North Atlantic and the Arctic Oceans, respectively. During the Holocene, Pb isotopes indicate synchronized weathering fluxes around the North Atlantic, whereas the influence of local weathering input on the Nd isotope evolution of the deep Nordic Seas ceased. Instead, the Holocene Nd isotope signal has been driven by the strength of the advection/convection of water masses in the study area. These new constraints on changes in the Nordic Seas provide important endmember information for Nd isotope based reconstructions of NADW export downstream in the Atlantic Ocean.

Description: Transgenerational effects of multiple stressors on marine organisms are emerging environmental themes. We thus experimentally tested for transgenerational effects of seawater acidification and hypoxia on the early development traits of the mussel Mytilus edulis. Fertilization rate, embryo deformity rate, and larval shell length were negatively impacted by acidification, while hypoxia had little effect except for increasing deformity rates under control pH conditions. Offspring from low pH/O2 parents were less negatively affected by low pH/O2 conditions than offspring from control parents; however, low pH/O2 conditions still negatively affected developmental traits in offspring from acclimated parents compared to control seawater conditions. Our results demonstrate that experimental seawater acidification and hypoxia can adversely affect early developmental traits of M. edulis and that parental exposure can only partially alleviate these impacts. If experimental observations hold true in nature, it is unlikely that parental exposure will confer larval tolerance to ocean acidification for M. edulis.

Description: The link between ecology and reproductive isolation constitutes the cornerstone of the ecological hypothesis of speciation. Such a link can arise when traits under ecologically based selection are also used as cues for mating (‘magic traits’) or as a by-product of habitat choice when mating takes place within habitats. Here, we propose that behavioural syndromes may also constitute such a link. We illustrate this mechanism in the butter hamlet, Hypoplectrus unicolor, a reef fish from the wider Caribbean, with aggressive mimicry as the focal ecological trait. Aggressive mimicry is of particular interest in hamlets since it has been proposed to play a key role in the radiation of Hypoplectrus. Individuals from a natural population in Bocas del Toro, Panama, were tagged and their diurnal and spawning behaviours observed over 2 years. The results indicate that aggressive mimicry behaviour differed consistently between individuals and formed two discrete behavioural types that also differed with respect to territoriality. Differences in territoriality between the two behavioural types translated into different use of space in spawning contexts, which generated a tendency for assortative mating by behavioural type. This case study illustrates how behavioural syndromes may form a link between ecologically relevant behavioural traits and mate choice, suggesting that they might play an underappreciated role in the early stages of speciation.

Description: Highlights • In-situ trace metal speciation in the Adriatic Sea by submersible voltammetric sensors • Metal species distribution mainly affected by Po River outflow. • Metal dynamic concentrations below legal limits • Cu dynamic concentrations toxic to sensitive phytoplankton Abstract Information on the distribution and speciation of trace metals is of critical importance for our ability to interpret the links between the bioavailability and uptake of an element, and its biogeochemical cycle in coastal environments. Within the framework of the European Project “In-situ automated Monitoring of Trace metal speciation in Estuaries and Coastal zones in relation with the biogeochemical processes (IMTEC)”, the chemical speciation of Cd, Pb and Cu was carried out along the Po River plume in the period 27 October – 2 November 2002. During the cruise, five Voltammetric In-situ Profiling systems and one Multi Physical Chemical Profiler, as well as conventional voltammetric instruments, were successfully applied in order to evaluate the distribution of Cd, Pb and Cu between different fractions (free ion, dynamic, colloidal, dissolved and particulate fractions) and to assess the evolution of these fractions during estuarine mixing and in the water column. Dynamic concentrations were 0.05–0.2 nmol L−1 Cd, 0.02–0.2 nmol L−1 Pb, and 0.15–4.0 nmol L−1Cu. Cd was mainly present as dynamic fraction (40–100% of the dissolved Cd). High proportions of Pb (~70%) and Cu (~80%) were present as colloids probably of biogenic origin. Principal components analysis reveals a strong influence of the Po River discharge on the spatial and vertical distributions of metal species. Almost all the metal fractions globally decreased following the salinity gradient. Metal concentrations are far below (at least one order of magnitude lower) the Environmental Quality Standard established by the Italian law. However, the Cu dynamic fraction showed concentrations likely to be toxic to sensitive phytoplankton community and to have negative effects on larva development of coastal macroinvertebrate species (toxicity data extracted from literature).

Description: Highlights • Systematic analysis of ship bathymetry enables segment scale geological mapping. • The Menez Gwen segment experiences magmatic periods every 300 to 500 ka. • Periods of enhanced magmatic activity are a regional phenomenon. • Hydrothermalism at Menez Gwen accompanies a waning, intense magmatic period. • Faulting and along-axis permeability variations focus hydrothermal venting. Abstract Slow-spreading mid-ocean ridges have the potential to form large seafloor massive sulphide (SMS) deposits. Current exploration for SMS deposits commonly targets associated active hydrothermal venting on the ridge axis, which makes the discovery of inactive vent sites and SMS deposits in the off-axis regions unlikely. Geological maps of the seafloor, which help understand the timing and location of SMS formation, usually focus on individual hydrothermal vent sites and their immediate surroundings, and are often too small to aid in SMS exploration. This study uses ship-based multibeam echosounder (MBES) data and a systematic classification scheme to produce a segment-scale geological map. When combined with spreading rate, this allows us to not only reconstruct the segment's spreading history, but also reveals important processes that localize hydrothermal venting. Geological mapping around two known hydrothermal vent sites on the Menez Gwen segment at 37°50′N on the slow-spreading Mid-Atlantic Ridge showed that hydrothermal venting accompanies the tectonic break-up of a large, cooling magmatic body. Venting is focussed by faulting and resulting permeability changes. The large magmatic body is associated with an axial volcano that formed as a last stage of a period with intense magmatic accretion. Such magmatic accretion periods occur every 300 to 500 ka at the Menez Gwen segment, with increasing intensity over the past 3.5 Ma years. The most recent, most intense magmatic period appears to be a regional phenomenon, also affecting the neighbouring Lucky Strike and Rifted Hills segments. Understanding the accretional setting and the spatial and temporal constraints of hydrothermal venting enables us to develop criteria in MBES data to aid exploration for inactive SMS deposits.

Description: Highlights • Generic geological model of hydrothermally extinct seafloor massive sulphide. • Sub-surface characterisation by combined drilling and geophysics. • New resource estimate for slow-spreading mid-ocean ridges. • Holistic approach to seafloor mineral deposits assessment. Abstract Deep-sea mineral deposits potentially represent vast metal resources that could make a major contribution to future global raw material supply. Increasing demand for these metals, many of which are required to enable a low-carbon and high-technology society and to relieve pressure on land-based resources, may result in deep sea mining within the next decade. Seafloor massive sulphide (SMS) deposits, containing abundant copper, zinc, gold and silver, have been the subject of recent and ongoing commercial interest. Although many seafloor hydrothermally systems have been studied, inactive SMS deposits are likely to more accessible to future mining and far more abundant, but are often obscured by pelagic sediment and hence difficult to locate. Furthermore, SMS deposits are three dimensional. Yet, to date, very few have been explored or sampled below the seafloor. Here, we describe the most comprehensive study to date of hydrothermally extinct seafloor massive sulphide deposits formed at a slow spreading ridge. Our approach involved two research cruises in the summer of 2016 to the TAG hydrothermal field at 26°N on the Mid-Atlantic Ridge. These expeditions mapped a number of hydrothermally extinct SMS deposits using an autonomous underwater vehicle and remotely operated vehicle, acquired a combination of geophysical data including sub-seafloor seismic reflection and refraction data from 25 ocean bottom instruments, and recovered core using a sub-seafloor drilling rig. Together, these results that have allowed us to construct a new generic model for extinct seafloor massive sulphide deposits that indicate the presence of up to five times more massive sulphide at and below the seafloor than was previously thought.

Description: Carbon dioxide (CO2) is the main greenhouse gas (GHG) and its atmospheric concentration is currently 50% higher than pre-industrial levels. The continuous GHGs emissions may lead to severe and irreversible consequences in the climate system. The reduction of GHG emissions may be not enough to mitigate climate change. Consequently, besides carbon capture from large emission sources, atmospheric CO2 capture may be also required. To meet the target defined for climate change mitigation, the removal of 10 Gt·yr−1 of CO2 globally by mid-century and 20 Gt·yr−1 of CO2 globally by the end of century. The technologies applied with this aim are known as negative emission technologies (NETs), as they lead to achieve a negative balance of carbon in atmosphere. This paper aims to present the recent research works regarding NETs, focusing the research findings achieved by academic groups and projects. Besides several advantages, NETs present high operational cost and its scale-up should be tested to know the real effect on climate change mitigation. With current knowledge, no single process should be seen as a solution. Research efforts should be performed to evaluate and reduce NETs costs and environmental impact.

Description: Highlights • Age and petrogenesis of the Miocene-Pleistocene proto Kermadec arc: the Kermadec and Colville Ridge • Complex interplay between element flux from the subducting Pacific Plate and heterogenous mantle wedge • New insights into the recent tectonic history of the Kermadec arc system Abstract The intra-oceanic Kermadec arc system extends ~1300 km between New Zealand and Fiji and comprises at least 30 arc front volcanoes, the Havre Trough back-arc and the remnant Colville and Kermadec Ridges. To date, most research has focussed on the Kermadec arc front volcanoes leaving the Colville and Kermadec Ridges virtually unexplored. Here, we present seven 40Ar/39Ar ages together with a comprehensive major and trace element and Sr-, Nd-, and Pb-isotope dataset from the Colville and Kermadec Ridges to better understand the evolution, petrogenesis and splitting of the former proto-Kermadec (Vitiaz) Arc to form these two remnant arc ridges. Our 40Ar/39Ar ages range from ~7.5–2.6 Ma, which suggests that arc volcanism at the Colville Ridge occurred continuously and longer than previously thought. Recovered Colville and Kermadec Ridge lavas range from mafic picro-basalts (MgO = ~8 wt%) to dacites. The lavas have arc-type normalised incompatible element patterns and Sr and Pb isotopic compositions intermediate between Pacific MORB and subducted lithosphere (including sediments, altered oceanic crust and serpentinised uppermost mantle). Geochemically diverse lavas, including ocean island basalt-like and potassic lavas with high Ce/Yb, Th/Zr, intermediate 206Pb/204Pb and low 143Nd/144Nd ratios were recovered from the Oligocene South Fiji Basin (and Eocene Three Kings Ridge) located west of the Colville Ridge. If largely trench-perpendicular mantle flow was operating during the Miocene, this geochemical heterogeneity was likely preserved in the Colville and Kermadec sub arc mantle. The Colville and Kermadec Ridge data therefore highlight the complex interplay between pre-existing mantle heterogeneities and material fluxes from the subducting Pacific Plate. The new data allow us to present a holistic (yet simplified) picture of the tectonic evolution of the late Vitiaz Arc and northern Zealandia since the Miocene and how this tectonism influences volcanic activity along the Kermadec arc at the present.

Description: Highlights • New experiments with melt inclusions in olivine at 1200 °C and 300 MPa. • Coupled behavior H2O and SiO2 in inclusions during re-hydration and dehydration. • SiO2 mobility results from formation/destruction of metal vacant olivine. • SiO2-undersaturated arc melt inclusions may originate by dehydration. • New method to assess initial H2O in dehydrated inclusions. Abstract Primary subduction-related magmas build up modern continental crust and counterbalance massive recycling of crustal material into the deep mantle occurring at this tectonic setting. Melt inclusions in Mg-rich olivine are believed to be the best probes of primary subduction-related melts. However, unexpectedly, most of such inclusions are SiO2-undersaturated, in contrast to predominantly SiO2-saturated island-arc rocks. The origin of these melts has been explained by melting of amphibole-bearing pyroxenites in the lower crust or upper mantle. The current models fail, however, to explain the high abundance of SiO2-undersaturated melts as well as their compositional difference with host rocks for the major elements but not for incompatible trace elements. Here we report results from the investigation of rocks and melt inclusions in olivine from Klyuchevskoy volcano in Kamchatka. We show that experimental re-hydration of SiO2-undersaturated melt inclusions in olivine Fo85−90 at 300 MPa pressure and 1200 °C causes a concomitant enrichment of melt in H2O and SiO2 so that re-hydrated inclusions (4–5 wt% H2O) become as silica-saturated as primitive Klyuchevskoy rocks. An experimental dehydration of previously re-hydrated inclusions also resulted in coupled depletion of melt in H2O and SiO2. The estimated stoichiometry of SiO2 and H2O gain/loss is consistent with dissolution/crystallization of metal-defect olivine on inclusion walls. The migration mechanism of water is controlled by hydrogen diffusion in the octahedral metal (Mg, Fe) vacancies through olivine structure as confirmed by FTIR spectroscopy. We conclude that the previously reported SiO2-undersaturated composition of many melt inclusions from hypersthene-normative island-arc rocks can be explained by the coupled loss of up to several weight percent of H2O and SiO2 from the initially trapped primitive SiO2-saturated hydrous melts. Thus, SiO2-undersaturated melt inclusions may not be representative of primitive island-arc magmas. The discovery of the coupled SiO2 and H2O loss from inclusions allowed us to propose a method for reconstruction of the initial water content even for completely dehydrated inclusions. The results of this study may indicate that the majority of primitive island-arc inclusions have not preserved their initial H2O content, and that primary arc melts contain on average ≥4 wt% H2O. The higher H2O concentration in primary arc melts implies the existence of a ‘crustal filter’ controlling the water content, which can be preserved in melt inclusions, and also the lower mantle melting temperatures and higher output H2O fluxes in subduction zones than previously estimated based on direct determination of H2O in potentially dehydrated melt inclusions.

Description: The Pb isotope compositions of galena in hydrothermal deposits obtained by drillings from two hydrothermal fields in the middle Okinawa Trough were studied. One of the study fields was the Iheya North field located on a volcanic complex and the other was the Izena field located in the sediment-filled caldera structure. LA-MC-ICP-MS was applied to directly measure Pb isotope compositions in individual galena grains which highlighted variations not only in regional scale, but also in microscopic scale so that changes of Pb isotope compositions within a galena grain can be tracked. Homogeneous Pb isotope compositions were found within the same hydrothermal site, irrespective of the mineral assemblage, texture and sampling depth beneath the seafloor. In contrast, the isotope compositions varied significantly between the two hydrothermal fields. The Pb isotope composition from the Iheya North field was isotopically close to the volcanic rocks of the Okinawa Trough, whereas that from the Izena field was more radiogenic with values intermediate between sediments and volcanic rocks of the Okinawa Trough. Within the Iheya North field, intra-field variation of Pb isotope compositions was recognized between two active sites 2.5 km apart from each other. The intra-field variation was recognized also in the Izena field. The sub-seafloor massive sulfide layer has a more sediment-like Pb isotope composition, compared to the inactive sulfide mound. These results illustrate that the Pb-mineralizing hydrothermal fluids originate from their local host rocks with/without sediment and that the isotope compositions of the galena grains reflect their metal sources; either the volcanic rocks and/or the sediments via water-rock interactions.

Description: Emplacement of Large Igneous Provinces (LIPs) had a major effect on global climate, ocean chemistries as traced in sedimentary records and biotic turnovers. The linkage between LIPs and oceanic anoxic events has been documented with the Cenomanian/Turonian boundary event and Oceanic Anoxic Event 2 (OAE2). The Caribbean LIP and High Arctic Large Igneous Province (HALIP) are regarded as possible triggers. The pericratonic Arctic Sverdrup Basin is the partial location of the HALIP, where little is known about sedimentary, geochemical and biotic responses to the HALIP phases. Sedimentary strata at Glacier Fiord, Axel Heiberg Island, exhibit a dynamic Cretaceous polar carbon burial history within the lower to middle Cenomanian Bastion Ridge Formation and upper Cenomanian to Turonian part of the Kanguk Formation. We present the first initial 187Os/188Os (Osi) composition profile for a polar Cenomanian/Turonian boundary interval (∼100–93.9 Ma) linked to recently dated magmatic phases of the Strand Fiord Formation, part of the HALIP. The carbon isotope record coupled with the Osi profile show two events in the upper Cenomanian interval marked by positive carbon perturbations and shifts to more non-radiogenic Osi compositions. The earlier short-lived event is interpreted as result of weathering of the surrounding Strand Fiord volcanics causing a local non-radiogenic Osi signal. Coinciding transgressive shorelines let to an increase in marine and terrestrially derived organic matter. Subsequently, injection of mantle-derived basalts into organic rich sediments is credited with causing the release of methane documented in a distinct negative carbon isotope excursion. We speculate that the methane release of the HALIP was an important contribution for rapid global warming caused by increasing atmospheric CO2 levels associated with the OAE2 event likewise recognized in the Sverdrup Basin. As climate cooled in the middle and late Turonian, carbon burial decreased under increasingly oxygenated benthic conditions. Epifaunal foraminiferal species, adapted to low oxygen conditions, persisted during the OAE2. Our Cenomanian to Turonian multiproxy record of the Sverdrup Basin distinguishes between local and global signals within a restricted High Arctic basin. Our results demonstrate the interplay between basin tectonism and sea-level change, increased weathering during transgressive phases, seafloor processes such as hydrothermal activity and methane release and biotic response to a complex paleoceanography. With future reliable dated frameworks this unique polar record will facilitate correlations to other polar basins and records of lower paleolatitudes.

Description: Highlights • Ritter Island's sector collapse provides an exemplar of volcanic tsunami hazards. • Deposit heterogeneity reflects erosion, secondary failure and a triggered eruption. • The volume of the distal deposit alone far exceeds the tsunamigenic failure. • A single catastrophic collapse led to stratigraphically complex distal deposits. • Accurate assessment of tsunami potential requires internal imaging and sampling. Abstract The current understanding of tsunamis generated by volcanic-island landslides is reliant on numerical models benchmarked against reconstructions of past events. As the largest historical event with timed tsunami observations, the 1888 sector collapse of Ritter Island, Papua New Guinea provides an outstanding opportunity to better understand the linked process of landslide emplacement and tsunami generation. Here, we use a combination of geophysical imaging, bathymetric mapping, seafloor observations and sampling to demonstrate that the Ritter landslide deposits are spatially and stratigraphically heterogeneous, reflecting a complex evolution of mass-flow processes. The primary landslide mass was dominated by well-bedded scoriaceous deposits, which rapidly disintegrated to form an erosive volcaniclastic flow that incised the substrate over much of its pathway. The major proportion of this initial flow is inferred to have been deposited up to 80 km from Ritter. The initial flow was followed by secondary failure of seafloor sediment, over 40 km from Ritter. The most distal part of the 1888 deposit has parallel internal boundaries, suggesting that multiple discrete units were deposited by a series of mass-flow processes initiated by the primary collapse. The last of these flows was derived from a submarine eruption triggered by the collapse. This syn-collapse eruption deposit is compositionally distinct from pre- and post-collapse eruptive products, suggesting that the collapse immediately destabilised the underlying magma reservoir. Subsequent eruptions have been fed by a modified plumbing system, constructing a submarine volcanic cone within the collapse scar through at least six post-collapse eruptions. Our results show that the initial tsunami-generating landslide at Ritter generated a stratigraphically complex set of deposits with a total volume that is several times larger than the initial failure. Given the potential for such complexity, there is no simple relationship between the volume of the tsunamigenic phase of a volcanic-island landslide and the final deposit volume, and deposit area or run-out cannot be used to infer primary landslide magnitude. The tsunamigenic potential of prehistoric sector-collapse deposits cannot, therefore, be assessed simply from surface mapping, but requires internal geophysical imaging and direct sampling to reconstruct the event.

Description: A detailed study of kinetics of reaction between hydrogen sulfide and orthorhombic cyclooctasulfur at environmentally relevant conditions, which results in formation of inorganic polysulfides, was performed. Rates of reaction were measured as a function of pH, temperature and concentrations of S2− and S0 in airtight stirred batch reactor. Reaction was carried out at [S0]/[S2−] 〈 0.1 in order to minimize a contribution of interfering reaction between orthorhombic cyclooctasulfur and polysulfides, which are stronger nucleophiles than sulfanide (HS−). Reaction was found to follow the 0.28 order with respect to activity of hydroxyl anion and first order with respect to concentrations of both hydrogen sulfide and orthorhombic cyclooctasulfur. The reaction activation energy was found to be 69 kJ mol−1. At conditions relevant for sulfidic marine sediments, the characteristic time of the reaction is c.a. 1 year. Relatively high activation energy of the reaction and distribution of polysulfide species testify to formation of polysulfides by a reaction between sulfanide and dissolved cyclooctasulfur rather than by direct nucleophilic dissolution of orthorhombic cyclooctasulfur.

Description: Anthropogenically-derived nitrogen input to the northern Indian Ocean has increased significantly in recent decades, based on both observational and model-derived estimates. This external nutrient source is supplied by atmospheric deposition and riverine fluxes, and has the potential to affect the vulnerable biogeochemical systems of the Arabian Sea and Bay of Bengal, influencing productivity and oceanic production of the greenhouse-gas nitrous-oxide (N 2 O). We summarize current estimates of this external nitrogen source to the northern Indian Ocean from observations and models, highlight implications for regional marine N 2 O emissions using model-based analyses, and make recommendations for measurement and model needs to improve current estimates and future predictions of this impact. Current observationally-derived estimates of deposition and riverine nitrogen inputs are limited by sparse measurements and uncertainties on accurate characterization of nitrogen species composition. Ocean model assessments of the impact of external nitrogen sources on regional marine N 2 O production in the northern Indian Ocean estimate potentially significant changes but also have large associated uncertainties. We recommend an integrated program of basin-wide measurements combined with high-resolution modeling and more detailed characterization of nitrogen-cycle process to address these uncertainties and improve current estimates and predictions.

Description: The Mauddud Formation, a late Albian-aged carbonate oil reservoir, is one of the main oil producers in Kuwait, however, it exhibits unreliable oil production from the Bahrah Field. The Mauddud Formation in the Bahrah field is divided into two sub-structures by a series of E-W faults and shows a slight degradation in oil quality (~5API) within the up-dip structure. Intersections of the E-W faults with NW-SE faults are associated with deep-seated seismic pipes, which culminate in pull-up features, creating the overlying sag-like features. Additionally, the Mauddud Formation shows evidence of baroque (saddle) dolomite in fracture cements and replacing clasts. Fluid inclusions within the baroque dolomite have abnormally high salinity (〉20 wt% NaCl eq), high homogenisation temperatures (up to ~100°C) and 3He/4He ratios ~0.3 times higher than atmospheric values. Taken together, this seismic and petrographic evidence suggests that the Mauddud Formation experienced an ingress of radiogenic, crustal fluids, potentially sourced from the basement. Seismic pipes, therefore, are interpreted to be the product of the upward movement of hydrothermal fluids that breach seal rocks, causing oil to escape and subsequent calcite cementation. An integrated map of a basement magnetic anomaly and current exhalative features on the present-day surface shows evidence of a relationship with fault locations on the level of the Mauddud Formation that were rejuvenated and associated with the remigration of oil. This study provides an exceptional example of a seal breach in one of the world’s most prolific hydrocarbon provinces. It also indicates the importance of a multidisciplinary, multi-scale approach extending from the basement to the surface in order to understand seal breach in carbonate petroleum systems. The overall data is used to assess the main factors that effected the integrity of the seal when this latter is breached by hydrothermal fluids.

Description: Highlights • We present a 5 myr record of biogeochemical cycling in a Cretaceous upwelling area. • A novel quantitative approach for the evaluation of Fe speciation proxies was applied. • Ferruginous proxy signature reflects intense chemical weathering rather than anoxia. • Water column redox conditions evolved from oxic to nitrogenous to euxinic before OAE2. • Smaller seawater nitrate inventory facilitated sedimentary H2S release and euxinia. Abstract Oceanic Anoxic Events (OAEs) in Earth's history are regarded as analogues for current and future ocean deoxygenation, potentially providing information on its pacing and internal dynamics. In order to predict the Earth system's response to changes in greenhouse gas concentrations and radiative forcing, a sound understanding of how biogeochemical cycling differs in modern and ancient marine environments is required. Here, we report proxy records for iron (Fe), sulfur and nitrogen cycling in the Tarfaya upwelling system in the Cretaceous Proto-North Atlantic before, during and after OAE2 (∼93 Ma). We apply a novel quantitative approach to sedimentary Fe speciation, which takes into account the influence of terrigenous weathering and sedimentation as well as authigenic Fe (non-terrigenous, precipitated onsite) rain rates on Fe-based paleo-redox proxies. Generally elevated ratios of reactive Fe (i.e., bound to oxide, carbonate and sulfide minerals) to total Fe (FeHR/FeT) throughout the 5 million year record are attributed to transport-limited chemical weathering under greenhouse climate conditions. Trace metal and nitrogen isotope systematics indicate a step-wise transition from oxic to nitrogenous to euxinic conditions over several million years prior to OAE2. Taking into consideration the low terrigenous sedimentation rates in the Tarfaya Basin, we demonstrate that highly elevated FeHR/FeT from the mid-Cenomanian through OAE2 were generated with a relatively small flux of additional authigenic Fe. Evaluation of mass accumulation rates of reactive Fe in conjunction with the extent of pyritization of reactive Fe reveals that authigenic Fe and sulfide precipitation rates in the Tarfaya Basin were similar to those in modern upwelling systems. Because of a smaller seawater nitrate inventory, however, chemolithoautotrophic sulfide oxidation with nitrate was less efficient in preventing hydrogen sulfide release into the water column. As terrigenous weathering and sediment flux determine how much authigenic Fe is required to generate an anoxic euxinic or ferruginous proxy signature, we emphasize that both have to be taken into account when interpreting Fe-based paleo-redox proxies.

Description: Highlights • Cell-reorganization; commissure: muti-cell-layered, central shell: single-cell-layered. • Individual fibres are secreted by several cells at the same time. • Tight cooperation of cells for the coordinated secretion of organic membrane and mineral. • Lack of extrapallial space between OME cells and developing fibres. • Mineral transport to sites of mineralization occurs via ion transport through cell membrane. Abstract To understand mineral transport pathways for shell secretion and to assess differences in cellular activity during mineralization, we imaged with TEM and FE-SEM ultrastructural characteristics of outer mantle epithelium (OME) cells. Imaging was carried out on Magellania venosa shells embedded/etched, chemically fixed/decalcified and high-pressure frozen/freeze-substituted samples from the commissure, central shell portions and from puncta. Imaging results are complemented with morphometric evaluations of volume fractions of membrane-bound organelles. At the commissure the OME consists of several layers of cells. These cells form oblique extensions that, in cross-section, are round below the primary layer and flat underneath fibres. At the commissure the OME is multi-cell layered, in central shell regions it is single-cell layered. When actively secreting shell carbonate extrapallial space is lacking, because OME cells are in direct contact with the calcite of the forming fibres. Upon termination of secretion, OME cells attach via apical hemidesmosomes to extracellular matrix membranes that line the proximal surface of fibres. At the commissure volume fractions for vesicles, mitochondria and lysosomes are higher relative to single-cell layered regions, whereas for endoplasmic-reticulum and Golgi apparatus there is no difference. FE-SEM, TEM imaging reveals the lack of extrapallial space between OME cells and developing fibres. In addition, there is no indication for an amorphous precursor within fibres when these are in active secretion mode. Accordingly, our results do not support transport of minerals by vesicles from cells to sites of mineralization, rather by transfer of carbonate ions via transport mechanisms associated with OME cell membranes.

Description: Chromium (Cr) isotope fractionation is sensitive to redox changes and the Cr isotopic composition (δ53Cr) of sedimentary rocks has been used to reconstruct marine redox conditions and atmospheric oxygenation in the past. However, little is known about the behaviour of chromium isotopes across modern marine redox boundaries. We investigated Cr concentrations and δ53Cr variations in seawater and sediment across the Peruvian oxygen minimum zone (OMZ) to provide a better understanding of Cr cycling in the ocean. We found that seawater δ53Cr values ranged from 0.02 ± 0.16‰ to 0.59 ± 0.11‰ (2SD) and sediment values from 0.31 ± 0.07 to 0.92 ± 0.12‰. Neither Cr concentrations nor δ53Cr values in the water column revealed significant shifts across the oxic-anoxic boundaries. Instead, processes that operate at a local scale, such as Cr scavenging by Fe-rich particles and Cr release from reducing sediments, are identified as the main controls on Cr concentrations and isotope compositions in the water column. The δ53Cr values of sediments deposited in permanently anoxic waters (0.77 ± 0.19‰, n = 5) are significantly different from the δ53Cr values of sediments deposited in oxic bottom waters (0.46 ± 0.19‰, n = 4). This suggests that sediment Cr concentrations and δ53Cr values are to some extent influenced by water column redox (e.g. reductive dissolution and transport of Fe oxides) and/or early diagenetic (e.g. redistribution of Cr during phosphogenesis) processes as well as biologic activity. Our data demonstrate that local scale water column redox gradients and sediment exchange can lead to a large range of δ53Cr values in sediments, comparable to the range found in the entire geologic record to date. Given the increasing prominence of Cr isotope measurements in constraining atmospheric oxygenation in deep time, we argue that the processes influencing Cr cycling under different conditions and from the water column to the sediment need to be better resolved to verify the utility of such measurements as paleoenvironmental proxies.

Description: The formation and segregation of oceanic and continental crust from the mantle, and its return to the mantle via subduction and/or delamination, leads to the development of distinct geochemical reservoirs in the terrestrial mantle. Fundamental questions remain regarding the location, nature, and residence time of these reservoirs, as well as the respective roles of oceanic and continental crust in the development of the mantle's geochemical endmembers. The Lu-Hf and Sm-Nd isotope systems behave similarly in magmatic systems and together form the terrestrial mantle Hf-Nd isotopic array. Here we combine a geodynamic model of mantle convection with isotope and trace element (TE) geochemistry to investigate the evolution of the Hf-Nd mantle array. This study examines the sensitivity to: TE partition coefficients used in the formation of oceanic crust; density contrasts between subducting oceanic crust and the mantle; and the formation and recycling of continental crust. We show that the fractionation between the parent (Lu and Sm) and daughter (Hf and Nd) species needs to be higher than is indicated by partition coefficients determined from the present-day melting environment. This is consistent with the suggestion of deeper mantle melting earlier in Earth history and an increased role for residual garnet. Subduction and accumulation of dense oceanic crust produces a large mass of incompatible TE enriched material in the deep mantle. This deep mantle enrichment appears to play a more significant role than the extraction and recycling of continental crust in developing the Hf and Nd isotope and TE compositions of the mid-ocean ridge mantle source. The corollary of this result is that the formation of the continental crust plays a secondary role, contrary to the currently accepted paradigm. Nevertheless, the inclusion of continental crust formation and recycling produces a broader model mantle array, which better reproduces the spread in the natural data set. This model also produces the Hf and Nd isotope and TE compositions of the upper mantle and continental crust, as well as deep mantle compositions similar to those of plume-fed ocean island basalts. Our model is consistent with continental growth models based on the Lu-Hf isotopic composition of zircon, which suggest that 50–70% of the present-day mass of the continental crust is produced prior to 3 Ga, and that the recycling of continental crust becomes more prevalent after this time.

Description: Highlights • Biodegradation is a critical process that governs the fate of oil spilled subsea. • Current models use first-order decay of pseudo-components of the oil composition. • We simulated subsea oil spills varying composition, biodegradation rates, and droplet size. • The most important parameter affecting surfacing time and location was droplet size. • The choice of biodegradation model and rates was of secondary importance. Abstract Biodegradation is important for the fate of oil spilled in marine environments, yet parameterization of biodegradation varies across oil spill models, which usually apply constant first-order decay rates to multiple pseudo-components describing an oil. To understand the influence of model parameterization on the fate of subsurface oil droplets, we reviewed existing algorithms and rates and conducted a model sensitivity study. Droplets were simulated from a blowout at 2000 m depth and were either treated with sub-surface dispersant injection (2% dispersant to oil ratio) or untreated. The most important factor affecting oil fate was the size of the droplets, with biodegradation contributing substantially to the fate of droplets ≤0.5 mm. Oil types, which were similar, had limited influence on simulated oil fate. Model results suggest that knowledge of droplet sizes and improved estimation of pseudo-component biodegradation rates and lag times would enhance prediction of the fate and transport of subsurface oil.

Description: The Hikurangi Subduction Zone (HSZ), New Zealand, accommodates westward subduction of the Pacific Plate. Where imaged seismically, the shallow HSZ décollement (〈10–15 km depth) occurs within or along the upper contact of Late Cretaceous-Paleogene (70–32 million-year-old) sediments. The frictional properties of Paleogene sediments recovered from Ocean Drilling Program Leg 181, Site 1124 were measured at 60 MPa effective normal stress and varying sliding velocities (V = 0.3–30 µm/s) and temperatures (T = 25–225 °C). Velocity-stepping experiments were conducted at temperatures of 25 °C, 75 °C, 150 °C, and 225 °C to determine the friction rate parameter (a–b). Paleocene and Oligocene clay-bearing nannofossil chalks (μ = 0.45–0.61) and a middle Eocene clayey nannofossil chalk (μ = 0.35–0.51) are frictionally stronger than smectite-bearing Eocene clays (μ = 0.16–0.31). With increasing temperature, chalks show rate-strengthening to rate-weakening frictional stability trends; clays show rate-weakening and rate-neutral to rate-strengthening frictional stability trends. The results obtained from Site 1124 sediments indicate that: (1) fault-zone weakness may not require pore-fluid overpressures; (2) clays and chalks can host frictional instabilities; and (3) heterogeneous frictional properties can promote variable slip behaviour.

Description: Nitrous oxide (N2O) is a climate-relevant atmospheric trace gas. It is produced as an intermediate of the nitrogen cycle. The open and coastal oceans are major sources of atmospheric N2O. However, its oceanic distribution is still largely unknown. Here we present the first measurements of the water column distribution of N2O in the Gulf of Aqaba and the Red Sea. Samples for N2O depth profiles were collected at the time-series site Station A in the northern Gulf of Aqaba (June and September 2003, and February 2004) and at several stations in the central Red Sea (October 2014, January and August 2016). Additionally, we measured N2O concentrations in brine pool samples collected in the northern and central Red Sea (January 2005 and August 2016). In the Gulf of Aqaba, N2O surface concentrations ranged from 6 to 8 nmol L−1 (97–111% saturation) and were close to the equilibrium with the overlying atmosphere. A pronounced temporal variability of the N2O water column distribution was observed. We suggest that this variability is a reflection of the interplay between N2O production by nitrification and its consumption by N2 fixation in the layers below 150 m during summer. N2O surface concentrations and saturations in the central Red Sea basin ranged from 2 to 9 nmol L−1 (43–155% saturation). A pronounced temporal variability with significant supersaturation in October 2014 and undersaturation in January and August 2016 was observed in the surface layer. In October 2014, N2O in the water column seemed to result from production via nitrification. Low N2O water column concentrations in January and August 2016 indicated a significant removal of N2O. We speculate that either in-situ consumption or remote loss processes of N2O such as denitrification in coastal regions were responsible for this difference. Strong meso- and submesoscale processes might have transported the coastal signals into the central Red Sea. In addition, enhanced N2O concentrations of up to 39 nmol L−1 were found at the seawater-brine pool interfaces which point to an N2O production via nitrification and/or denitrification at low O2 concentrations. Our results indicate that the Red Sea and the Gulf of Aqaba are unique natural laboratories for the study of N2O production and consumption pathways under extreme conditions in one of the warmest and most saline regions of the global ocean.

Description: Highlights • Extensive set of 170 40Ar39Ar single-crystal ages for Cadamosto Seamount. • Volcanic eruption ages at Cadamosto Seamount are all young (〈 100 ka). • Three samples dominated by sanidine phenocrysts preserve a 21.04 ± 0.62 ka age. • Sanidine antecrysts in two samples show complex chemical zonation patterns. • Antecryst ages suggest long-lived magmatic activity in the seamount, up to 1.52 Ma. Abstract Cadamosto Seamount is located in the SW of the Cape Verde Archipelago in the central Atlantic Ocean off the west coast of Africa. Many radiometric dates exist for the islands in the archipelago; however, no geochronological information has been obtained from the numerous seamounts. The timescales for igneous processes in the submarine realm are thus poorly understood. In this study, we investigated five lavas that were sampled by dredging and ROV (remotely operated vehicle) from the flanks and summit areas of the largely phonolitic Cadamosto Seamount during two different research cruises. Chemical zonation patterns of minerals were determined by electron microprobe, and radiometric ages were obtained from single-crystal total-fusion and single−/multi-grain step-heating 40Ar39Ar analyses of sanidine, nepheline and sodalite-group minerals. Our 40Ar39Ar results reveal young sanidine eruption ages (all 〈100 ka) at Cadamosto Seamount: (1) Three western flank/summit lavas have a relatively simple petrology dominated by phenocrysts, and overlap with mean sanidine ages of 20.98 ± 0.87 ka, 21.44 ± 0.80 ka and 22.3 ± 2.0 ka, with a combined mean age of 21.04 ± 0.62 ka from the three samples (all uncertainties are quoted at 2σ). The remaining two samples from the summit/NE flank are dominated by complex zoned sanidines with resorbed antecrystic cores and phenocrystic rims. These samples yield older sanidine ages of 51.8 ± 2.4 ka and 97 ± 14 ka, which are interpreted to be maximum eruption ages. This is due to the dominance of antecrysts in these two samples and the possibility that the analyzed sanidine grains may be a mixture of older antecrystic cores and younger phenocrystic rims. The older 40Ar39Ar ages of many sanidine and nepheline antecrysts also give us clues regarding older magmatic events at Cadamosto Seamount, despite these grains having undergone resorption and phenocrystic rim overgrowths, resulting in some radiogenic 40Ar loss during entrainment in the subsequent magmas. The antecrysts minimum ages extend back to 1.5215 ± 0.0083 Ma, which supports the age progression of magmatism observed in the southern islands chain of the Cape Verde Archipelago. The youngest volcanic eruption period (21.14 ± 0.62 ka) occurred during the Last Glacial Maximum, a period of global sea level lowstands. We suggest that the comparatively rapid unloading leading up to the lowstand may have reduced pressure conditions within the Cadamosto Seamount magma plumbing system, and thus led to enhanced submarine eruption activity.

Description: It is hypothesized that pH fluctuations produced by seagrasses metabolism may confer marine calcifiers resistance to ocean acidification. Here, we tested this thesis by comparing the net population growth rate (NPGR) of a foraminifer species (Rosalina sp.) epiphytic of Mediterranean seagrass (Posidonia oceanica) to average current and projected pH scenarios under either stable conditions or diel fluctuations in pH of 0.3 units; variations similar to that experienced in their habitat. No significant differences were found in NPGRs between the fluctuating and stable pH treatments at current pH levels. NPGRs in treatments where pH fluctuated did not present significant differences to the treatment with high and stable pH conditions. In contrast, foraminifers exposed to stable low pH regimes experienced a steep decline in NPGR. These results suggest that diel pH fluctuations generated by P. oceanica photosynthetic activity could confer resistance to ocean acidification to Rosalina sp.

Description: Fossil brachiopod shells are often used as valuable archives to reconstruct paleoenvironmental conditions in deep time. However, biomineralization processes can impact their fidelity as geochemical proxies. Brachiopod shells comprise an outer primary layer, a secondary fibrous layer and sometimes, a tertiary columnar layer. Therefore, it is essential to assess the potential effects of the biomineralization processes in each of the different shell microstructures of modern brachiopods. This study analyses the oxygen isotopic composition together with Li/Ca, Na/Ca Mg/Ca and Sr/Ca data at high spatial (20-50 μm) resolution in seven modern brachiopod species, focusing on differences between the primary, secondary and tertiary layers. In all studied species, δ18O values of the outer primary layer are consistently out of equilibrium with seawater. Also, this shell layer is enriched in Li, Na, Mg and Sr. Contrary to the primary layer, the innermost secondary layer is near or at oxygen isotopic and elemental equilibrium with ambient seawater. The columnar tertiary shell layer, if present, has the least variable and the heaviest oxygen isotopic composition, within the range of equilibrium values with seawater. This tertiary layer, however, is depleted in minor and trace elements relative to the other shell layers. Thus, the tertiary layer is more suitable for oxygen isotopic studies, whereas the innermost secondary layer of the most mature parts of the shell is the best target in two-layered shells. While we do not observe any clear interspecific relationships between Mg/Ca and Sr/Ca ratios, on one hand, and environmental parameters such as temperature, salinity and pH, on the other hand, there is a positive interspecific relationship between Na/Ca and salinity and a negative interspecific relationship between Li/Ca and temperature, suggesting their potential use as proxies of physicochemical parameters of seawater.

Description: High latitude deep water upwelling has the potential to control global climate over glacial timescales through the biological pump and ocean-atmosphere CO2 exchange. However, there is currently a lack of continuous long nutrient upwelling records with which to assess this mechanism. Here we present geochemical proxy records for nutrient upwelling and glacial North Pacific Intermediate Water (GNPIW) formation in the Bering Sea over the past 850 kyr, which demonstrates that glacial periods were characterised by reduced nutrient upwelling, when global atmospheric CO2 and temperature were also lowered. We suggest that glacial expansion of sea ice in the Bering Sea, and the simultaneous expansion of low nutrient GNPIW, inhibited vertical mixing and nutrient supply across the subarctic Pacific Ocean. Our findings lend support to the suggestion that high latitude sea ice and the resultant intermediate water formation, modulated deep water upwelling and ocean-atmosphere CO2 exchange on glacial-interglacial timescales.

Description: Fluid flow patterns at cold seeps provide insights into the mechanism and influence of methane emission into the ocean, which is critical in its environmental impact assessment. Here, we report pore fluid compositions of three ~8 m long piston cores (QDN-14A, QDN-14B and R1) collected from the newly-discovered active Haima cold seeps on the northwestern slope of the South China Sea. Reaction-transport models were further applied to quantify related biogeochemical processes and to reveal the patterns of fluid flow. Extremely low δ13C values (〈 -52‰) of dissolved inorganic carbon (DIC) near the sulfate-methane transition in the three cores suggest that anaerobic oxidation of methane is the predominant biogeochemical process. The presence of small pieces of gas hydrates along with negative anomalies of porewater chloride and sodium concentrations reflects gas hydrate dissociation. Nearly invariable concentrations of sulfate, DIC, and calcium on a meter-scale were observed in the uppermost part of the sediment cores QDN-14A and QDN-14B. This irrigation-like feature is inferred to result from enhanced methane flux in QDN-14A and QDN-14B. We infer that lateral migration of methane-rich fluids from R1 site to QDN-14A and QDN-14B sites together with upward migrated methane is responsible for the enhanced methane flux. This speculation is supported by the occurrence of gas hydrates which might have clogged the fluid channel in the seepage center (R1) and driven the transportation of methane-bearing fluid along a coarser sediment layer in surrounding sediments (QDN-14A and QDN-14B). The proposed scenario is further demonstrated using a non-steady-state modeling that reconstructed the porewater irrigation-like feature assuming an increased methane flux. The modeling result predicts that gas-hydrate formation in core R1 started at least 150 yr B.P. The proposed fluid flow pattern within a localized seep site may have a great implication for understanding the heterogeneity of sedimentary records.

Description: Highlights • Novel multi-disciplinary approach to tracing freshwater and particle transport into boundary currents; • Significant glacial inputs reach coastal waters and are transported rapidly offshore; • Low surface water dissolved silicon concentrations maintained by diatom activity despite strong glacial and benthic supplies. Abstract Biogeochemical cycling in high-latitude regions has a disproportionate impact on global nutrient budgets. Here, we introduce a holistic, multi-disciplinary framework for elucidating the influence of glacial meltwaters, shelf currents, and biological production on biogeochemical cycling in high-latitude continental margins, with a focus on the silica cycle. Our findings highlight the impact of significant glacial discharge on nutrient supply to shelf and slope waters, as well as surface and benthic production in these regions, over a range of timescales from days to thousands of years. Whilst biological uptake in fjords and strong diatom activity in coastal waters maintains low dissolved silicon concentrations in surface waters, we find important but spatially heterogeneous additions of particulates into the system, which are transported rapidly away from the shore. We expect the glacially-derived particles – together with biogenic silica tests – to be cycled rapidly through shallow sediments, resulting in a strong benthic flux of dissolved silicon. Entrainment of this benthic silicon into boundary currents may supply an important source of this key nutrient into the Labrador Sea, and is also likely to recirculate back into the deep fjords inshore. This study illustrates how geochemical and oceanographic analyses can be used together to probe further into modern nutrient cycling in this region, as well as the palaeoclimatological approaches to investigating changes in glacial meltwater discharge through time, especially during periods of rapid climatic change in the Late Quaternary.

Description: Highlights • Three distinct types of carbonates exist in cold seeps in the Okinawa Trough. • Carbonate forms between lower part of SMTZ and upper part of methanogenic zone. • Hydrothermal has the potential to foster Fe-AOM in cold seep sediment. • Metal-AOM might have an influence on early Earth's methane flux and metal cycle. Abstract Anaerobic oxidation of methane (AOM) is an important process that regulates methane budget in the global carbon cycle. Sulfate is traditionally regarded as the most important electron acceptor for AOM. However, recent studies reveal that reactive metal reduction-driven AOM (metal-AOM) may also present on natural environments. Partitioning the methane-C sink from anaerobic oxidation between sulfate reduction-driven AOM (sulfate-AOM) and metal-AOM is thus becoming a scientific challenge to be addressed. This study aimed to show that metal-AOM has a potential to complement sulfate-AOM, especially when methane seeps met sediments enriched in iron and manganese oxides supplied by hydrothermal plumes. Samples of authigenic carbonate were collected from the cold seeps on the western slope of the Okinawa Trough (OT), a semi-enclosed back-arc basin with cold seeps and hydrothermal activities coexist spatially. Petrologic and mineralogical observations provided faithful evidence of a close genetic relationship between goethite and authigenic carbonates, likely indicating the presence of metal-AOM although some contributions of organoclastic Fe reduction cannot be ruled out. The most possible place of metal-AOM was between the lower part of the sulfate–methane transition zone (SMTZ) and the immediate upper part of the methanogenic zone. The characteristics of δ13Ccarb [−53.7‰ to −3.3‰ Vienna-PeeDee Belemnite (VPDB)] also point to our carbonate samples as the products of AOM. These authigenic carbonates was further identified as three possible types of carbonate of different sources: sulfate-AOM, metal-AOM, and hydrothermal carbonates, depending on the correlations among concentrations of carbonate-associated sulfate (CAS), δ13Ccarb, and δ18Ocarb. Based on these findings, we tentatively suggested that the reduction of reactive metals carried by hydrothermal plumes might drive the methane oxidation in the adjacent cold seep areas, resulting in the precipitation of unique carbonates and enhancement the efficiency of “the benthic methane filter”. This study reported the coupling or interaction between the two extreme submarine environments by metal-AOM for the first time, which might help in understanding and improving the global carbon and metal cycles now and in the past. Previous article in issue

Description: Highlights: • A remarkable increase in PFASs levels was found in the Japan Sea from 2005 to 2010. • The inventory of PFASs in whole water mass was firstly assessed in semi-closed sea. • The annual ΣPFASs inflow from the East China Sea to the Japan Sea was around 70.8 t. • The PFASs vertical profile in the Mediterranean Sea implied a few pollution sources. • PFOA predominated in the Japan Sea, the Mediterranean Sea, and the East China Sea. Abstract: Perfluoroalkyl substances (PFASs) have become an important class of global environmental contaminants, yet their vertical profile in the marine water column is still less understood, especially for the semi-closed seas. In this study, the contamination level and spatial distribution of 8 PFASs were investigated in both surface and vertical water samples from two semi-closed seas, the Japan Sea and the Mediterranean Sea. Similar levels and compositions of PFASs were found between these two seas. The vertical profile of PFASs in the Mediterranean Sea was variable while that was relatively steady in the Japan Sea, probably due to their different pollution sources. The accumulation rate of PFASs from the East China Sea to the Japan Sea was calculated, for which perfluorooctanesulfonic acid and perfluorooctanoic acid were found to have high accumulation potency in both surface and deep water; most of the investigated PFASs were accumulated in the deep water due to the long residence time while they were more likely to escape to the Pacific Ocean in the surface water. This work aimed (i) to study the distribution of PFASs in both surface and vertical water samples in two semi-closed seas, namely the Japan Sea and for the first time the Mediterranean Sea, (ii) to assess the temporal trend in the Japan Sea, and (iii) to firstly investigate the potential transport of PFASs from the East China Sea and Taiwan Strait in order to estimate the inventory of PFASs in whole water mass in the Japan Sea.

Description: Picoeukaryotes are an important, diverse and spatially variable component of marine microbial communities. However, little is known of their distribution in response to environmental heterogeneity. In this study, to understand the Nordic Seas picoeukaryotic community, eleven surface samples from different water bodies were collected in June 2015. Archaeplastida, mainly Prasinophyceae, was present in all samples and was the largest component in cold waters, while Rhizaria and Alveoata were most abundant in the samples influenced by warm waters. Multivariate analyses showed that samples could be discriminated into groupings, each with its specific dominant species and community structure could precisely reflect the environmental heterogeneity caused by different water masses. This study details the relationships between the picoeukaryotes and complex currents in the Nordic Seas, and provides insight for application of using picoeukaryotes as indicator in future bioassessment for arctic or boreal waters.

Description: Highlights • Strong ocean stratification in the Fram Strait during the late glacial (33–26 ka). • Breakup of ocean stratification during the LGM (26–20 ka) due to enhanced upwelling. • No extreme aging of 〉6000 yr in the Arctic Mediterranean as previously suggested. Abstract The present-day ocean ventilation in the Arctic Mediterranean (Nordic Seas and Arctic Ocean), via transformation of northward inflowing warm Atlantic surface water into cold deep water, affects regional climate, atmospheric circulation and carbon storage in the deep ocean. Here we study the glacial evolution of the Arctic Mediterranean circulation and its influence on glacial climate using radiocarbon reservoir-age reconstructions on deep-sea cores from the Fram Strait that cover the late glacial period (33,000–20,000 yr ago; 33–20 ka). Our results show high Benthic-Planktic 14C age differences of ∼1500 14C years 33–26.5 ka suggesting significant water column stratification between ∼100–2600 m water depth, and reduction and/or shoaling of deep-water formation. This phase was followed by break-up of the stratification during the Last Glacial Maximum (LGM; 26–20 ka), with Benthic-Planktic 14C age differences of ∼250 14C years, likely due to enhanced upwelling. These ocean circulation changes potentially contributed to the final intensification phase of glaciation via positive cryosphere-atmosphere-ocean circulation-carbon cycle feedbacks. Our data also do not support ‘extreme aging’ of 〉6000 14C years in the deep Arctic Mediterranean, and appear to rule out the proposed outflow of very old Arctic Ocean water to the Nordic Seas during the LGM and to the subpolar North Atlantic Ocean during the deglacial period.

Description: This article describes the biodiversity of gelatinous macrozooplankton and presents quantitative field data on their community composition and distribution pattern in the North Sea during August 2018. The data set consists of jellyfish and comb jelly species abundance estimates which are based on sampling at 62 stations in the central and southern North Sea covering Danish waters, the German Bight, waters off the Dutch coast as well as the western North Sea off the UK coast and the central North Sea. The sampling gear was a 13 m long MIK-net (modified Methot Isaac Kidd net; Ø 2 m, mesh size 1 mm, mesh size cod end 500 μm) deployed in double oblique hauls from the surface to 5 m above the sea floor. Samples were visually analysed for gelatinous macrozooplankton (〉2 mm) using a light table. Samples were processed within 1 hour after catch. In total, 6239 gelatinous macrozooplankton specimen were caught. Spatial distribution pattern described in this article include the jellyfish species Aequorea sp., Aurelia aurita, Beroe sp., Chrysaora hysoscella, Clytia hemisphaerica, Cyanea capillata, Cyanea lamarckii, Eirene viridula, Leuckartiara octona, Melicertum octocostatum, Obelia sp. as well as the comb jelly species Mnemiopsis leidyi and Pleurobrachia pileus. Further, size frequency distributions of abundant taxa are provided together with a summary of abundances as well as average, maximum and minimum sizes of all species. This dataset has not previously been published and is of high value for comparison with other – and future - investigations of gelatinous macrozooplankton in the North Sea. The data were obtained during an internationally coordinated, standard fishery survey which is carried out annually (Quarter 3 – North Sea – International Bottom Trawl Survey – Q3 NS-IBTS). The gained information could be used as baseline for a monitoring of potential changes in gelatinous macrozooplankton abundances to address the long standing question if gelatinous zooplankton are on the rise due to climate change induced stressors.

Description: Marine phytoplankton can regulate their stoichiometric composition in response to variations in the availability of nutrients, light and the pH of seawater. Varying elemental composition of photoautotrophs affects several important ecological and biogeochemical processes, e.g., primary and export production, nutrient cycling, calcification, and grazing. Here we compare two plankton ecosystem models that consider regulatory mechanisms of cellular carbon and nitrogen, driving the physiological acclimation of photoautotrophs. The Carbon:Nitrogen Regulated Ecosystem Model (CN-REcoM) and the optimality-based model (OBM) differ in their representation of phytoplankton dynamics, i.e. nutrient acquisition, synthesis of chlorophyll a, and growth. All other model compartments (zooplankton, detritus, dissolved inorganic and organic matter) and processes (grazing, aggregation, remineralisation) remain identical in both models. We assess the skills of the two models against data from an ocean acidification mesocosm experiment with three CO2 treatments. Neither model accounts for any carbon dioxide (CO2) effects explicitly. Instead, we assimilate data of the different CO2 treatments separately into the models. Thereby we aim at identifying optimal model parameter values that might correlate with differences in CO2 conditions. For the OBM, optimal parameter estimates of Qmin (subsistence N:C ratio) and V (maximum potential photosynthesis rate of photoautotrophs) turned out to be higher for mesocosms exposed to high CO2 compared to those with low CO2 concentrations. By contrast, a similar correlation is not observed for the CN-REcoM. A possible physiological interpretation of higher estimates of Qmin and V according to the OBM is that phytoplankton may experience environmental stress under more acidic conditions, and hence must invest more energy/resources for maintaining basic cellular functions. Our data assimilation reveals that the parameters of the OBM are better constrained by the data than those of the CN-REcoM. Furthermore, the OBM is better able than CN-REcoM to reproduce data that were not used for parameter optimization.

Description: Highlights • We report on methane seeps found at shallow depths on New Zealand's Hikurangi Margin. • Tools have been applied to measure bubble characteristics from video footage and to estimate the gas flow rate using acoustic data. • We estimate that the entire Tuaheni seep field produces somewhere in the range of 30–2415 t of methane per year. • The density of seeps at this location is far greater than anything else observed on the Hikurangi Margin. Abstract We analyse an area of high density submarine methane gas seeps situated on the shelf to slope transition (130–420 m water depth) on the northern region of New Zealand's Hikurangi margin, off Poverty Bay. Multibeam and singlebeam echo sounder data collected in 2014 and 2015 revealed 〉600 seeps, at much greater density than any previously mapped areas of seepage on the Hikurangi margin. To broadly constrain the output of methane from these seeps, we have estimated the flow of methane at individual seeps, utilising perspective-measurements applied to still frames from a deep towed camera system to measure the dimensions of rising bubbles. We combine bubble size and rise-rate distributions with singlebeam acoustic data to estimate gas flow rates at six selected seeps sites. Our results predict a wide range (3.0–2249 mL/min) of methane release into the water column. If we assume that the six seeps we analysed are representative of the entire seep population, and that gas flow is constant, we can extrapolate across the seep field and infer a gas release of 30 to 2415 t of methane per year into the ocean.

Description: Highlights: • Sponges, evolutionary basal animals, represent a reservoir of novel viral diversity • Viromes of neighboring sponges are individually unique and species specific • Phages encode ankyrins to aid bacteria in evading the eukaryotic immune system • Such “Ankyphages” are widespread in host-associated environments, including humans Summary: Phages are increasingly recognized as important members of host-associated microbiomes, with a vast genomic diversity. The new frontier is to understand how phages may affect higher order processes, such as in the context of host-microbe interactions. Here, we use marine sponges as a model to investigate the interplay between phages, bacterial symbionts, and eukaryotic hosts. Using viral metagenomics, we find that sponges, although massively filtering seawater, harbor species-specific and even individually unique viral signatures that are taxonomically distinct from other environments. We further discover a symbiont phage-encoded ankyrin-domain-containing protein, which is widely spread in phages of many host-associated contexts including human. We confirm in macrophage infection assays that the ankyrin protein (ANKp) modulates the eukaryotic host immune response against bacteria. We predict that the role of ANKp in nature is to facilitate coexistence in the tripartite interplay between phages, symbionts, and sponges and possibly many other host-microbe associations.

Description: Describing the pore habit of methane hydrate in sediment matrices is essential for understanding natural distribution of methane hydrate, methane trace (transport and solidification) in the hydrate stability zone, physical properties of hydrate-bearing sediments, and the associated influence on potential gas production. Pore habit visualization in natural media at pore scale even with laboratory synthesized cores has been challenging due to the similar densities of methane hydrate from pore liquid. In this work, we used phase-contrast assisted micro-CT with potassium iodine-doped brine to visualize four phases: sand particles, pore fluid, methane hydrate and methane gas. This study visualizes the pore habit of methane hydrate at various stages including during hydrate formation in excess-gas systems, its evolution after brine injection to replace pore fluid, and hydrate formation in excess-water systems. Hydrate tends to adopt round and smooth surfaces when in contact with water while exhibits relatively angular interfaces when in contact with methane gas. Hydrate formation in excess-gas systems results in a partial cementing and partial mineral-coating pore habit, while hydrate in excess-water systems develops mainly as pore-filling, and locally cementing or mineral-coating where big gas pockets exist at the initial state. Pore liquid replacement from methane gas to brine triggers a shift of hydrate pore habit towards pore-filling. Methane hydrate evolution over time produces bigger hydrate particles but with less contact area with sand particles. The effects of hydrate pore habit become less important as hydrate particle size exceeds the pore size. Additionally, hydrate formation could trap residual methane gas and brine as inclusions.

Description: The physical properties of natural gas hydrate-bearing sediments are critical for the analysis of natural systems and for the design of gas production strategies. This work explores the properties of fine-grained sediments containing segregated hydrate lenses. Our analyses show that hydrate formation is grain-displacive when the product of the effective stress and the grain radius is σ′R 〈 2πΓhw ≈ 0.2-to-0.3 N/m, such as in shallow fine-grained sediments. The assessment of physical properties is particularly challenging in fine-grained sediments with segregated gas hydrate because (1) inherent difficulties in hydrate formation hinder laboratory studies, and (2) segregated hydrate requires large specimens and laboratory devices to avoid boundary effects and to create a representative volume for analysis. We circumvent these challenges through the use of numerical simulations. In these simulations, the properties of the hydrate-free sediment surrounding the segregated hydrate lenses take into consideration the effects of cryogenic suction and grain-displacive hydrate growth. Our results for mechanical properties and conduction show that numerical simulations must properly consider the hydrate morphology, the altered sediment properties, and the sediment-hydrate interfacial conditions (interfaces are rough, jagged and well bonded during hydrate formation, but become weak-frictional on dissociation). In fact, changes in the strength and stiffness of the hydrate-free sediment that surrounds a segregated hydrate mass can be more important on the global properties than the presence of hydrate itself. Numerical simulations highlight distinct anisotropy in mechanical properties and conduction in the presence of segregated hydrate lenses, and the tendency to shear localization when there is a weak-frictional interface. We emphasize that a relatively small fraction of fines can make sediments prone to segregated hydrate formation, therefore proper sediment classification is critical.

Description: Harmful invader ctenophore Mnemiopsis leidyi's expansions in the Eurasian Seas, its spatio-temporal population dynamics depending on environmental conditions in recipient habitats have been synthesized. M. leidyi found suitable temperature, salinity and productivity conditions in the temperate and subtropical environments of the semi-enclosed seas, in the coastal areas of open basins and in closed water bodies, where it created autonomous populations. M. leidyi changes its phenology depending on seasonal temperature regime in different environments. We assessed ranges of sea surface temperature, sea surface salinity and sea surface chlorophyll values, sufficient for M. leidyi general occurrence and reproduction based on comprehensive long-term datasets, contributed by co-authors. This assessment revealed that there are at least two eco-types (Southern and Northern) in the recipient seas of Eurasia with features specific for their donor areas. The range of thresholds for M. leidyi establishment, occurrence and life cycle in both eco-types depends on variability of environmental parameters in their native habitats.

Description: Continental flood basalts (CFB) are amongst the most voluminous volcanic eruptions in Earth's history. They are rapidly emplaced, and in rare cases the thick lava piles are associated with primitive magmas that have high MgO contents. The compositions of these primitive melts are consistent with a deep-sourced, high-temperature mantle plume origin. Whilst the association of CFBs with impacting mantle plumes is widely accepted, the magnitude of the thermal anomaly is not yet resolved. The development of Al-in-olivine thermometry, however, allows the crystallisation temperature of (near-)liquidus olivine to be determined without knowing the composition of the co-existing melt. This provides both a robust minimum estimate of mantle temperature and a value from which potential temperature (TP) can be back-calculated. This technique has previously confirmed that crystallisation temperatures in CFB settings can be a few hundred degrees greater than those estimated for MORB, and the results hint at a diversity in crystallisation temperatures between different CFB settings. In this study, we re-assess the TP of the mantle source of the Paraná-Etendeka CFB province by applying the Al-in-olivine thermometer to olivine–spinel pairs from picrites and ferropicrites. We show that the mean crystallisation temperature of olivine with Fo〉90 in the picrites is 1458 °C, with a maximum temperature of 1511 °C. Using the mean value, we calculate a preferred TP of 1623 °C, for an assumed lithospheric thickness of 50 km and magma emplacement pressure of 0.5 GPa. This represents a thermal anomaly of around +300 °C relative to ambient mantle, and confirms that the mantle source of the Paraná-Etendeka CFB is the second hottest known from Phanerozoic Large Igneous Provinces, after the Caribbean Large Igneous Province. The ferropicrites record a cooler mean olivine crystallisation temperature of 1296 °C. Given that these low-volume melts derive from deeper and earlier melting of mantle pyroxenite, their temperature is not directly comparable to that of the picrites but they appear to require a somewhat cooler mantle source – perhaps found at the front or edges of a rising plume head.

Description: From oxic atmosphere to metallic core, the Earth's components are broadly stratified with respect to oxygen fugacity. A simple picture of reducing oxygen fugacity with depth may be disrupted by the accumulation of oxidised crustal material in the deep lower mantle, entrained there as a result of subduction. While hotspot volcanoes are fed by regions of the mantle likely to have incorporated such recycled material, the oxygen fugacity of erupted hotspot basalts had long been considered comparable to or slightly more oxidised than that of mid-ocean ridge basalt (MORB) and more reduced than subduction zone basalts. Here we report measurements of the redox state of glassy crystal-hosted melt inclusions from tephra and quenched lava samples from the Canary and Cape Verde Islands, that we can independently show were entrapped prior to extensive sulphur degassing. We find high ferric iron to total iron ratios (Fe3+/∑Fe) of up to 0.27–0.30, indicating that mantle plume primary melts are significantly more oxidised than those associated with mid-ocean ridges and even subduction zone. These results, together with previous investigations from the Erebus, Hawaiian and Icelandic hotspots, confirm that mantle upwelling provides a return flow from the deep Earth for components of oxidised subducted lithosphere and suggest that highly oxidised material accumulates or is generated in the lower mantle. The oxidation state of the Earth's interior must therefore be highly heterogeneous and potentially locally inversely stratified.

Description: While the impact of ocean warming on single species is well described, the impact on marine biofouling communities is not well understood. Effluents of power plants have higher temperatures and can be used as natural large-scale test sites to investigate warming effects on marine ecosystems. In the present study, we evaluated the impact of elevated temperatures in the vicinity of a power plant on macro-biofouling communities in the northern coast of the Persian Gulf. The impact site was on average 2 °C warmer than the control site. Our results demonstrate a significantly different structure and composition of biofouling communities between control and impact sites. Warming led to a 1.5-fold increase in the mean coverage of biofouling communities and slightly decreased functional and species richness. Our results indicated that future warming will likely increase biofouling pressure, while decreasing diversity of communities, particularly in habitats where organisms exist at their upper tolerance limits of temperature.

Description: Highlights • Determination of the tectonomagmatic evolution of the NW Atlantic • Mapping of the breakup-related magmatism using the vocanostratigraphy concept • Mapping of the magnetic and gravimetric crustal domain patterns and their boundaries using integrated SGM method • Analyses of seabed and onshore samples and field analogues work • New plate tectonic reconstruction for the NW Atlantic Abstract Passive margins are the locus of tectonic and magmatic processes leading to the formation of highly variable along-strike and conjugate margins structures. Using extensive new seismic, gravity, and magnetic datasets, complemented by seabed samples and field work, we investigate the tectonomagmatic evolution of the northwest (NW) Atlantic where breakup-related igneous rocks were emplaced during several Paleogene events associated with lithospheric stretching, continental breakup, and the formation of new oceanic basins. Interpretational methods include integrated seismic-gravity-magnetic (SGM) interpretation and seismic volcanostratigraphy. In addition, seabed and field samples were collected and analyzed to constrain the basin stratigraphy, hydrocarbon potential, and the geochronology and geochemistry of the volcanic sequences. Offshore, 2D seismic data reveal several Seaward Dipping Reflector (SDR) wedges and escarpments in the Labrador Sea, Davis Strait, and Baffin Bay. Onshore, eastward prograding foreset-bedded hyaloclastite delta deposits and overlying horizontal lava successions outcrop on Nuussuaq. These hyaloclastites and lava successions are world class analogues to the Lava Delta and Landward Flows volcanic seismic facies units identified offshore. Our mapping results document an aerial extent of the Paleogene breakup-related volcanics of 0.3 × 106 km2, with an estimated volume of 0.5–0.6 × 106 km3. Basalt samples recovered by dredging the Upernavik Escarpment have late Paleocene to/early Eocene ages, whereas the sedimentary samples provide an excellent seismic tie with the stratigraphy and the geology in this frontier area. From the integrated SGM interpretation, we identify a rapidly thinning crust and changes in top and intra-basement seismic reflection characteristics in the oceanic domain correlated with transition between different magnetic domains. The mapping results were subsequently integrated in a plate tectonic model. The plate tectonic reconstruction and basalt geochronology suggest that the majority of the volcanism in the NW Atlantic occurred between ~62 and ~58 Ma, associated with an increased spreading rate in the Labrador Sea, starting from the onset of the Selandian (~61.6 Ma). A change in the spreading direction during the Eocene (~56 Ma), synchronously with a shift of volcanic activity from the NW to the NE Atlantic, correspond to a northward drift of Greenland and the initiation of the Eurekan Orogeny. Finally, our interpretations reveal a complex rift configuration along the NW Atlantic conjugate margins both prior to and during breakup.

Description: Highlights • Major eruption of Ilopango volcano, El Salvador occurred in the first half of the 6th century. • Ilopango eruption is consistent with ‘mystery’ eruption of 540 CE that caused global cooling. • Magnitude 7 event ranks as one of the 10 largest on Earth in past 7000 years. • Impacts on the Maya of Central America were severe, including estimated 100,000 + fatalities. Abstract Ilopango volcano (El Salvador) erupted violently during the Maya Classic Period (250–900 CE) in a densely-populated and intensively-cultivated region of the southern Maya realm, causing regional abandonment of an area covering more than 20,000 km2. However, neither the regional nor global impacts of the Tierra Blanca Joven (TBJ) eruption in Mesoamerica have been well appraised due to limitations in available volcanological, chronological, and archaeological observations. Here we present new evidence of the age, magnitude and sulfur release of the TBJ eruption, establishing it as one of the two hitherto unidentified volcanic triggers of a period of stratospheric aerosol loading that profoundly impacted Northern Hemisphere climate and society between circa 536 and 550 CE. Our chronology is derived from 100 new radiocarbon measurements performed on three subfossil tree trunks enveloped in proximal TBJ pyroclastic deposits. We also reassess the eruption magnitude using terrestrial (El Salvador, Guatemala, Honduras) and near-shore marine TBJ tephra deposit thickness measurements. Together, our new constraints on the age, eruption size (43.6 km3 Dense Rock Equivalent of magma, magnitude = 7.0) and sulfur yield (∼9–90 Tg), along with Ilopango's latitude (13.7° N), squarely frame the TBJ as the major climate-forcing eruption of 539 or 540 CE identified in bipolar ice cores and sourced to the tropics. In addition to deepening appreciation of the TBJ eruption's impacts in Mesoamerica, linking it to the major Northern Hemisphere climatic downturn of the mid-6th century CE offers another piece in the puzzle of understanding Eurasian history of the period.

Description: Quest is a fully integrated Carbon Capture and Storage (CCS) project that started CO2 injection in August of 2015. The Quest CCS Project is located near Fort Saskatchewan, Alberta, Canada. It includes a capture facility which uses a Shell amine technology, a pipeline of about 65 km length, and three injection well pads. Each injection well pad has an injection well, a deep monitoring well, and shallow groundwater wells. The storage complex is geologically defined by the injection reservoir, a deep saline aquifer called the Basal Cambrian Sand (BCS) (about 45 m thick) and several seals, including the Middle Cambrian Shale (about 50 m thick) and Lotsberg Salts (about 120 m thick). As of August 2018, over three million tonnes of CO2 have been safely injected and permanently stored in the BCS. The Alberta Carbon Competitiveness Incentive Regulation (CCIR) requires the use of standard methods of quantification for reporting greenhouse gas (GHG) emissions for facilities with over 100,000 tonnes of carbon dioxide equivalent (CO2e) per year. An emission offset project is required to comply with CCIR, associated standards and protocols, to demonstrate a reduction in the specified gas emissions and, in the case of Quest, geological sequestration. Quest is the first CCS project to implement an offset project in the context of commercial scale on-shore CO2 geological sequestration within a saline aquifer. Quest uses the Quantification Protocol for CO2 Capture and Permanent Storage in Deep Saline Aquifers, from Alberta Environment and Parks. An offset project must develop an offset project plan (OPP) which demonstrates how the project meets the requirement of the protocol, describes how GHG emissions reductions are achieved, identifies risks associated with the quantification of emission reduction benefits, and describes methodologies used to quantify sources and sinks. Subsequent to completing the OPP, an offset project will put together offset project reports (OPR) to report on the net reductions of GHG emissions for a specific period. The intent of this paper is a) to provide an overview of the OPP and OPR for the Quest CCS project, and b) to discuss learnings from the initial compilation and submission of offset project reports. The key learning at this time is associated to the equipment improvements to the injection gas online analyzer.

Description: The apicomplexans are a group of obligate animal pathogens that include Plasmodium (malaria), Toxoplasma (toxoplasmosis), and Cryptosporidium (cryptosporidiosis) [1]. They are an extremely diverse and specious group but are nevertheless united by a distinctive suite of cytoskeletal and secretory structures related to infection, called the apical complex, which is used to recognize and gain entry into animal host cells. The apicomplexans are also known to have evolved from free-living photosynthetic ancestors and retain a relict plastid (the apicoplast), which is non-photosynthetic but houses a number of other essential metabolic pathways [2]. Their closest relatives include a mix of both photosynthetic algae (chromerids) and non-photosynthetic microbial predators (colpodellids) [3]. Genomic analyses of these free-living relatives have revealed a great deal about how the alga-parasite transition may have taken place, as well as origins of parasitism more generally [4]. Here, we show that, despite the surprisingly complex origin of apicomplexans from algae, this transition actually occurred at least three times independently. Using single-cell genomics and transcriptomics from diverse uncultivated parasites, we find that two genera previously classified within the Apicomplexa, Piridium and Platyproteum, form separately branching lineages in phylogenomic analyses. Both retain cryptic plastids with genomic and metabolic features convergent with apicomplexans. These findings suggest a predilection in this lineage for both the convergent loss of photosynthesis and transition to parasitism, resulting in multiple lineages of superficially similar animal parasites.

Description: With increased global warming, cyanobacteria are blooming more frequently in lakes and reservoirs, severely damaging the health and stability of aquatic ecosystems and threatening drinking water safety and human health. There is an urgent demand for the effective prediction and prevention of cyanobacterial blooms. However, it is difficult to effectively reduce the risks and loss caused by cyanobacterial blooms because most methods are unable to successfully predict cyanobacteria blooms. Therefore, in this study, we proposed a new cyanobacterial bloom occurrence prediction method to analyze the probability and driving factors of the blooms for effective prevention and control. Dominant cyanobacterial species with bloom capabilities were initially determined using a dominant species identification model, and the principal driving factors of the dominant species were then analyzed using canonical correspondence analysis (CCA). Cyanobacterial bloom probability was calculated using a newly-developed model, after which, the probable mutation points were identified and thresholds for the principal driving factors of cyanobacterial blooms were predicted. A total of 141 phytoplankton data sets from 90 stations were collected from six large-scale hydrology, water-quality ecology, integrated field surveys in Jinan City, China in 2014–2015 and used for model application and verification. The results showed that there were six dominant cyanobacterial species in the study area, and that the principal driving factors were water temperature, pH, total phosphorus, ammonia nitrogen, chemical oxygen demand, and dissolved oxygen. The cyanobacterial blooms corresponded to a threshold water temperature range, pH, total phosphorus (TP), ammonium nitrogen level, chemical oxygen demand, and dissolved oxygen levels of 19.5–32.5 °C, 7.0–9.38, 0.13–0.22 mg L−1, 0.38–0.63 mg L−1, 10.5–17.5 mg L−1, and 4.97–8.28 mg L−1, respectively. Comparison with research results from other global regions further supported the use of these thresholds, indicating that this method could be used in habitats beyond China. We found that the probability of cyanobacterial bloom was 0.75, a critical point for prevention and control. When this critical point was exceeded, cyanobacteria could proliferate rapidly, increasing the risk of cyanobacterial blooms. Changes in driving factors need to be rapidly controlled, based on these thresholds, to prevent cyanobacterial blooms. Temporal and spatial scales were critical factors potentially affecting the selection of driving factors. This method is versatile and can help determine the risk of cyanobacterial blooms and the thresholds of the principal driving factors. It can effectively predict and help prevent cyanobacterial blooms to reduce the global probability of occurrence, protect the health and stability of water ecosystems, ensure drinking water safety, and protect human health.

Description: Lake Van, the largest soda lake in the world, is a key area where climatic changes are recorded by well-preserved sedimentary successions. In spite of the existence of such sequences, the ancient lake levels are still under debate. Here, we present U/Th ages of tufa layers exposed along the northern margin of the lake near the town of Adilcevaz. Tufa are interpreted to form during humid and temperate climate conditions in the contact zone between the highly alkaline lake water – rich in bicarbonate and carbonate ions – and calcium-rich groundwater. These contact zones most likely appear near shore. Thus, U/Th ages and altitude of the tufa present minimum ancient lakestands. The tufas obtained in our study are dated between 112.7 and 19.3 ka. They are interpreted to record two transgressional intervals, the first starting at 1701 meters above sea level (masl) altitude at 112.7 ka reaching 1706 masl at 72.5 ka (based on three U/Th ages). The second transgression starts at the present Lake Van level of 1646 masl at 30.1 ka, reaching 1725 masl at 19.3 ka (based on 15 U/Th ages). Comparison with climate proxies reveals that the first transgression was caused by intensified precipitation accompanied by warming, while the second transgression was triggered mainly by warming that initiated melting of glaciers. The lake-level fluctuations described here are almost in line with the ones gathered from dated lake terraces but contradict lake-level reconstruction based on pore water salinity.

Description: We present new field data from three outcrops of Miocene methane-derived authigenic carbonates in the foredeep of the northern Apennines that contain chemosynthetic fauna and record a long history (∼1 Ma) of shallow fluid seepage linked to seafloor anaerobic oxidation of methane. The studied outcrops show similar features in terms of carbonate morphology, facies, spatial distribution and lateral and vertical contacts with the enclosing sediments. Methane-derived carbonates occur in two structural positions: 1) on the slope of the accretionary wedge in hemipelagites draping buried thrust-related anticlines, and 2) at the leading edge of the deformation front in the inner foredeep, within fault-related anticlines standing above the adjacent deep seafloor as intrabasinal ridges. We compare fossil seeps with two extensively investigated modern analogues: the Hikurangi Margin, offshore New Zealand and Hydrate Ridge, on the Cascadia margin, offshore the U.S.A. These analogues share a similar compressive structural setting and are marked by the presence of variably extensive and voluminous methane-derived carbonate bodies and chemosynthetic fauna on the present-day seafloor. The comparison allows us to propose a model for the evolution of fluid seeps on thrust-related ridges. At the deformation front, uplift and geometry of the anticlinal ridges are controlled by the growth of splay faults, mostly blind, connected to the basal detachment, favoring the migration of fluids toward the incipient anticline. Fold development generates extensional stresses in the hinge zone of the anticline, promoting the development of normal faults; fluid migration pathways and seafloor seeps shift from the forelimb toward the crest of the ridge as the structures evolve. In the slope setting, far from the deformation front, thrust faults and extensional faults in buried anticlines remain the main fluid migration pathways to sustain seepage at the seafloor. After reaching a mature stage within the wedge, the structure is less active and buried in the slope environment of the evolved prism.

Description: Seismic imaging techniques are widely used to determine fluid migration pathways in the subsurface. Understanding the timing and distribution of focused fluid migration pathways is important for assessing reservoir seal quality and hydrocarbon exploration risk, as well as seafloor biogeochemical processes in the case of fluid venting from the seafloor. The frontier Canterbury Basin southeast of New Zealand is well studied, but questions remain regarding the dynamic movement of fluids through the basin. Using 3D seismic data combined with high-resolution boomer seismic data, we characterise focused fluid migration and sediment remobilisation events in the Canterbury Basin. We show how polygonal fault formation and nucleation is affected in the vicinity of vertically ascending fluids and sediments. A cylindrical region devoid of polygonal faulting around the feeder system of a buried sediment volcano points to the possible existence of an axisymmetrical stress field induced by upward migrating fluids and sediments. Sediment remobilisation and intrusions of permeable stingers (i.e. sand injectites) could enable dewatering of their host strata and thereby prevent polygonal faults from nucleating. Amplitude variations with angle (AVA) and a detailed analysis of two tiers of polygonal faults reveal three phases of fluid migration and sediment remobilisation and intrusion through, and into, low permeability sediments. Our integrated conceptual model provides insights into vertical fluid migration mechanisms and the implications for polygonal fault formation.

Description: The composition and distribution of the phytoplankton community on the southweastern Brazilian continental shelf and continental slope were evaluated through chemotaxonomic analyses (HPLC-CHEMTAX). The samples were collected during five oceanographic cruises from 2012 to 2014 in spring and autumn. Fourteen surface blooms of Trichodesmium (slicks) were registered during the field surveys. The Trichodesmium biomass was estimated by both pigment analyses and microscope counts, with significant correlation found between the methods, except in some slicks. However, myxoxanthophyll, a Trichodesmium pigment biomarker generally used in CHEMTAX, was detectable only in seven samples from stations with Trichodesmium slicks, indicating that their use in pigment chemotaxonomic approaches should be taken with caution, because it could lead to errors in the estimation of Trichodesmium biomass. Four water masses were identified at the surface: Plata Plume Water (PPW), Subtropical Shelf Water (STSW), Shelf Water (SW) and Tropical Water (TW). The identified water masses seem to be the main driving factor influencing the composition, distribution and biomass of phytoplankton groups in the study region. The salty-warm oligotrophic TW, associated with the Brazil Current, was the dominant surface water mass in both autumn and spring. The surface waters in this work were generally associated with low values of both total chlorophyll a (TChl a) and nutrient concentration. In no slicks conditions, surface TChl a concentration was low ranging between 0.04 and 2.44 mg m−3 (mean 0.27 mg m−3) in almost all oceanographic stations. The highest biomass concentrations were recorded in stations under influence of both PPW and STSW. Overall, Prochlorococcus, haptophytes, Synechococcus, and Trichodesmium dominated the phytoplankton community and their contributions were above 70% to total Chl a in both spring and autumn. The other phytoplankton groups (prasinophytes, cryptophytes and dinoflagellates) represented a minor fraction, with values below 15% of the total biomass. A Canonical Correspondence Analysis showed that Prochlorococcus, haptophytes, Synechococcus and Trichodesmium were related with both TW and SW and were also positively associated with weaker water column stability, a deeper mixed layer, temperature and salinity. In turn, cryptophytes, dinoflagellates, prasynophytes and diatoms, mainly associated with STSW and PPW, were positively correlated with higher stability and nutrients (nitrogen and phosphorus), and negatively associated with both temperature and salinity. Our results showed that the pigment analysis (HPLC-CHEMTAX) allowed a detailed mapping of phytoplankton communities' distribution in the south and southeastern Brazilian continental shelf and shelf-break, and that the Trichodesmium biomass, as currently estimated by this approach, should be carefully revised.

Description: Rivers and estuaries are among the main entrances of litter to the marine environment. This study characterizes marine litter deposits in three estuaries of the Gulf of Biscay, assesses its potential impact in estuarine habitats based on expert elucidation, and develops a methodology to estimate the associated environmental risk. Litter was ubiquitous in the estuaries of study, mostly represented by plastic debris and sanitary waste. High marsh communities acted as litter traps, showing significantly higher litter densities than adjacent habitats. The expected impact was valued to be low but different across habitats and possible litter-habitat interactions. The estimated risk was low but different across habitats and estuaries, determined by the probability of encounter and the expected impact. This study contributes to increase the scarce knowledge available on the threat that marine litter poses in estuarine environments and presents a methodology to help identify those habitats under a higher risk.

Description: The ability of a community to absorb environmental change without undergoing structural modification is a hallmark of ecological resistance. The recognition that species interactions can stabilize community processes has led to the idea that the effects of climate change may be less than what most considerations currently allow. We tested whether herbivory can compensate for the expansion of weedy algae triggered by CO2 enrichment and warming. Using a six-month mesocosm experiment, we show that increasing per capita herbivory by gastropods absorbs the boosted effects of CO2 enrichment on algal production in temperate systems of weak to moderate herbivory. However, under the combined effects of acidification and warming this compensatory effect was eroded by reducing the diversity, density and biomass of herbivores. This loss of functionality combined with boosted primary productivity drove a fourfold expansion of weedy algal species. Our results demonstrate capacity to buffer ecosystems against CO2 enrichment, but loss of this capacity through ocean warming either in isolation or combined with CO2, driving significant algal turf expansion. Identifying compensatory processes and the circumstances under which they prevail could potentially help manage the impacts of ocean warming and acidification, which are further amplified by local disturbances such as habitat loss and herbivore over-exploitation.

Description: Ongoing and past biome transitions are generally assigned to climate and atmospheric changes (e.g. temperature, precipitation, CO2), but the major regional factors or factor combinations that drive vegetation change often remain unknown. Modelling studies applying ensemble runs can help to partition the effects of the different drivers. Such studies require careful validation with observational data. In this study, fossil pollen records from 741 sites in Europe, 728 sites in North America, and 418 sites in Asia (extracted from terrestrial archives including lake sediments) are used to reconstruct biomes at selected time slices between 40 cal ka BP (calibrated thousand years before present) and today. These results are used to validate Northern Hemisphere biome distributions (〉30°N) simulated by the biome model BIOME4 that has been forced with climate data simulated by a General Circulation model. Quantitative comparisons between pollen- and model-based results show a generally good fit at a broad spatial scale. Mismatches occur in central-arid Asia with a broader extent of grassland throughout the last 40 ka (likely due to the over-representation of Artemisia and Chenopodiaceae pollen) and in Europe with over-estimation of tundra at 0 cal ka BP (likely due to human impacts to some extent). Sensitivity analysis reveals that broad-scale biome changes follow the global signal of major postglacial temperature change, although the climatic variables vary in their regional and temporal importance. Temperature is the dominant variable in Europe and other rather maritime areas for biome changes between 21 and 14 ka, while precipitation is highly important in the arid inland regions of Asia and North America. The ecophysiological effect of changes in the atmospheric CO2-concentration has the highest impact during this transition than in other intervals. With respect to modern vegetation in the course of global warming, our findings imply that vegetation change in the Northern Hemisphere may be strongly limited by effective moisture changes, i.e. the combined effect of temperature and precipitation, particularly in inland areas.

Description: A crucial part of any equilibrium modelling calculation is the selection of equilibrium constants that quantify the strength of interactions between metals and ligands. For researchers new to the field of solution chemistry, locating suitable equilibrium constants that lead to reliable model results can be problematic. Numerous large compilations of equilibrium constant values have been published each having their own limitations, coverage and availability. This work surveys eleven major compilations of equilibrium constants including those from authoritative groups such as IUPAC, NIST, and NEA. For each compilation surveyed, details are given related to the historical background and underlying project, scope of the database with respect to range of included metals and ligands, and the present-day availability of publications or computer databases resulting from the project. The various methods employed by different data compilers in their critical assessment for each compilation are also discussed.

Description: The eastern slope of Mt. Etna is characterised by shallow seismicity originating from normal-oblique faulting, Timpe Fault System, related to WNW-ESE regional extension. Recent research has demonstrated that in the fault population of Mt. Etna's eastern flank the minimum earthquake magnitude that will have a ground rupture effect is ca. 2.5. This system is characterised by high frequency seismic activity, due to thinned seismogenic crustal layer. This characteristic, together with the high density of the fault segments, does not always for identification of the segments responsible for the earthquake. The earthquakes, affecting the medium-lower eastern flank, have been historically reconstructed by macroseismic analysis and reported in a macroseismic database, and in recent decades by instrumental seismic registration, which provide the seismological parameters capable of evaluating focal mechanism, hypocentre and relative algorithms related to geometric parameters which control the growth of fault segments. In this paper, we present a methodology to evaluate the age of the rapid exhumation of the free-face fault plane of the NNW-SSE oriented normal fault segment named S. Tecla (Timpe Fault System). It consists of the measurement of the thalli species (Lichenometry method) in order to evaluate the parameters which characterise their growth. The seismic history of the S. Tecla Fault indicates eight certain events from 1865 to 2005 with 3.4 ÷ 4.7 Magnitude (De Guidi et al., 2012 and reference therein). We found evidence of two different recent rapid vertical deformation events at the base of the S. Tecla fault escarpment, the oldest 20 m long and 0.25 m in height, and the youngest with a 0.02 m high nude surface exposed. We have observed that there are thalli of Xanthoparmelia conspersa (Ehrh. Ex Ach.) Hale, colonizing part of the nude surface on the escarpment. The results highlight that the oldest thalli was dated at 43.7 years old, showing that rapid vertical deformation generated the surface where the thalli, after 4 years, took root. The displacement of this surface could be related to the seismic events occurring on 3rd August 1973 (3.8 M) in S. M. Ammalati area probably accompanied by intense post seismic deformation. The second and last event could be attributable to a 3.1 M seismic event occurring on 25th September 2014 (ISIDe, 2016).

Description: The calcite shells, or tests, of foraminifera provide a window into Earth history because they are archived in most marine sediments and contain useful geochemical proxies for paleoceanography. Previous observations of diurnal heterogeneity in proxies like Mg/Ca demonstrate a complex relationship between environmental conditions and test composition. The causes for this diurnal banding and the potential impact for proxy interpretation in systems other than Mg/Ca have yet to be determined. Recently, Mg and Na in shells of the planktic foraminifer species Orbulina universa have been observed to be high at the location of the primary organic sheet (POS), i.e. the organic template upon which the calcite test is formed. Here we use time-of-flight secondary ion mass spectrometry (ToF-SIMS), a chemical and isotope mapping technique with a spatial resolution of 300 nm, to show that Na banding is a consistent feature in the tests of 45 individual cultured O. universa. This banding occurs in two distinct forms: (1) sharp Na bands associated with organic sheets that are embedded in the calcite test after chamber formation; and (2) regular, thicker, but lower-amplitude Na bands that are found throughout the test. We use the pattern of the first type of banding to indicate the extent and sequence of calcite growth during chamber formation. Specifically, we show that new chamber formation involves growth over the previous chamber in Orbulina bilobata, a morphotype of O. universa that develops a second partial spherical chamber attached to the primary sphere. This is consistent with a bilamellar model of foraminiferal growth. However, a SIMS mapping survey of the morphologically more complex Globigerina bulloides and Neogloboquadrina dutertrei suggests that the pattern of growth during chamber formation and the prevalence of different types of Na bands may be species-specific. The wide, repeating Na bands that occur throughout the test of O. universa generally occur in an inverse pattern with respect to Mg banding for the first few days of the foraminifer's life, but this pattern changes as the organism ages. We use the magnitude, timing, and coherency between Na and Mg bands to put constraints on various proposed mechanisms for banding, including antiport Mg2+-2Na+ exchange and kinetic growth rate effects.

Description: This study investigates the Lesser Antilles fore-arc at the latitude of Guadeloupe Archipelago and evidences that La Désirade Island, the eastermost island of the forearc, displays a staircase coastal sequence including four uplifted marine terraces and an upper reefal platform with mean shoreline angle elevations ranging from 10 to 210 m above sea level (asl). The platform paleobathymetry is constraint by a detailed analysis of the sediments. We propose a revised morphostratigraphy for this coastal sequence including 5 paleo-shorelines based on six U/Th dating from aragonitic corals from the three lowest terraces combined with paleobathymetric analysis of the fossil corals present in the upper platform. Terrace and upper platform carving of construction periods occurred during Marine Isotopic Stages MIS 5e, MIS 9, and during the intervals MIS 15–17, MIS 19–25 and MIS 31–49 (upper coral reef platform). Our results evidence a bulk decreasing uplift rate since early Calabrian to Present-Day, clearly documented since 310 ka (MIS 9) (from 0.14 to 0.19 to ca 0 mm/y). Our data are consistent with first the transient influence of the subducting oceanic Tiburon ridge during Calabrian, then with other parametres of the subduction zone since late Calabrian to Present-Day (dip of the slab, basal erosion of the upper plate, inherited structures …)

Description: Elevated concentrations of carbon dioxide are a common stressor for fish and other aquatic animals. In particular, intensive aquaculture can impose prolonged periods of severe environmental hypercapnia, manifold exceeding CO2 concentrations of natural habitats. In order to cope with this stressor, gills are essential and constitute the primary organ in the acclimatization process. Yet, despite a general understanding of changes in ion regulation, not much is known with regard to other cellular mechanisms. In this study, we apply RT-qPCR to investigate changes in the expression of several genes associated with metabolism, stress and immunity within gills of juvenile turbot (Psetta maxima) after an eight-week exposure to different concentrations of CO2 (low = ~3000 μatm, medium = ~15000 μatm and high = ~25000 μatm CO2). Histological examination of the gill tissue only found a significant increase of hypertrophied secondary lamella in the highest tested treatment level. gene expression results, on the other hand, implied both, mutual and dose-dependent transcriptional adjustments. Comparable up-regulation of IL-1ß, LMP7 and Grim19 at medium and high hypercapnia indicated an increase of reactive oxygen species (ROS) within gill cells. Simultaneous increase in Akirin and PRDX transcripts at medium CO2 indicated enhanced anti-oxidant activity and regulation of transcription, while reduced mRNA concentrations of COX, EF1α and STAT2 at high CO2 denoted suppressed protein synthesis and reduced metabolic capacity. In addition to upregulated DFAD and ApoE expression, implying compensating repair measures, gills exposed to the highest tested treatment level seemed to operate close to or even beyond their maximum capacity. Thus, fitting the model of capacity limitation, our results provide evidence for accretive intracellular hypoxia and oxidative stress in the gills of turbot, dependent on the level of environmental hypercapnia. Further, genes, such as COX, may be valuable biomarkers when attempting to discriminate between a successful and an overpowered stress response.

Description: Highlights • Northern Hispaniola Margin is studied with new high-resolution bathymetry and vintage seismic data. • Northern Hispaniola Deformed Belt forms an active N-verging fold-and-thrust imbricate system. • Gravity failures are frequent features in the Northern Hispaniola Margin and Bahamas Banks slope. • Oblique collision accelerates the Bahamas Carbonate Province collapse and retreat. • New observations help the assessment of tsunami hazards in the Northern Caribbean region. Abstract The northern margin of Hispaniola records the oblique collision/underthrusting of the Bahamas Carbonate Province with the island-arc. Due to the collision, northern Hispaniola has suffered several natural disasters caused by major earthquakes and tsunamis, such as the historic earthquake of 1842, the tsunami caused by earthquake-driven slumping in 1918 in the Mona Passage, the seismic crisis of 1943–1953 with five events of M 〉 7.0 or the seismic crisis of 2003 with a main shock of M6.3 and a large aftershock of M5.3. Using new swath multibeam bathymetry data and vintage single- and multi-channel seismic profiles, we have performed a regional scale analysis and interpretation of the shallow surface and active processes along the northern margin of the Dominican Republic. We have identified three morphostructural provinces: a) the Bahamas Banks, b) the Hispaniola Trench and c) the Insular Margin, which are divided into two tectonic domains, the Collision Domain and Underthrusting Domain. The southern slope of the Bahamas Carbonate Province shows a very irregular morphology produced by active erosive processes and normal dip-slip faulting, evidence of an extensional tectonic regime and margin collapse. This collapse is of major extent in the Oblique Collision Domain where there are erosive and fault escarpments with higher dip-slip fault throws. The Hispaniola Trench, is formed by the Caicos and Hispaniola basins in the underthrusting domain, and by the Santisima Trinidad and Navidad basins in the Oblique Collision Domain. They have a flat seafloor with a sedimentary filling of variable thickness consisting of horizontal or sub-horizontal turbiditic levels. The turbiditic fill mostly proceeds from the island arc through wide channels and canyons, which transports sediment from the shelf and upper slope. The Insular Margin comprises the Insular Shelf and the Insular Slope. The active processes are generated on the Insular Slope where the Northern Hispaniola Deformed Belt is developed. This Deformed Belt shows a very irregular morphology, with a WNW-ESE trending N verging imbricate thrust-and fold system. This system is the result of the adjustment of the oblique collision/underthrusting between the North American plate and the Caribbean plate. In the Oblique Underthrusting Domain the along-strike development of the imbricate system is highly variable forming salients and recesses. This variability is due to along-strike changes in the sediment thickness of the Hispaniola Trench, as well as to the variable topography of the underthrusting Bahamas Carbonate Province. In the Oblique Collision Domain, the morphology of the Insular Slope and the development of the Deformed Belt deeply change. The imbricate system is barely inferred and lies upslope. These changes are due to the active collision of Bahamas Carbonate Province with the Insular Margin where the spurs are indented against the Insular Margin. Throughout the entire area studied, gravitational instabilities have been observed, especially on the Insular Margin and to a lesser extent on the southern slope of the Bahamas Carbonate Province. These instabilities are a direct consequence of the active underthrusting/collision process. We have mapped large individual slumps north of Puerto Plata in the Oblique Underthrusting Domain and zones of major slumps in the Oblique Collision Domain. These evidences of active processes must be considered as near-field sources in future studies on the assessment of tsunami hazards in the region.

Description: Dissolved neodymium (Nd) and its radiogenic isotope composition (143Nd/144Nd, expressed as εNd) belong to the key parameters of the international GEOTRACES program, which aims to investigate the processes controlling the distribution of trace elements and their isotopes in the global ocean. We present Nd isotope and concentration ([Nd]) data from eleven full depth water column profiles from the eastern (sub)tropical Atlantic Ocean between 2°N and 29°N and from the Romanche Fracture Zone sampled during Meteor cruise M81/1 (GEOTRACES cruise GA11) in February/March 2010. The εNd signatures range from −12.9 in upper North Atlantic Deep Water (UNADW) at the equator to −8.1 in the mixed layer near the Canary Islands. Nd concentrations range from 11.9 pmol/kg observed within the Equatorial Undercurrent to 40.2 pmol/kg in Antarctic Bottom Water (AABW) in the Romanche Fracture Zone. Large variations in surface water Nd isotope compositions (−12.7 ≤ εNd ≤ −8.1) and concentrations (15.7 pmol/kg ≤ [Nd] ≤ 27.7 pmol/kg) are caused by partial dissolution of Saharan dust particles between 2°N and 13°N and volcanic island weathering (Canaries) between 25°N and 29°N. In contrast to dust inputs, which predominantly affect the Nd concentrations and isotope compositions of surface waters and underlying South Atlantic Central Water (SACW), contributions originating from the Canary Islands affect the Nd isotope composition of the entire surrounding water column without significantly altering Nd concentrations, thus confirming the concept of boundary exchange in its strictest sense. The results confirm that the composition of lower North Atlantic Deep Water (LNADW, εNd = −12.1) in the abyssal plains of the eastern North Atlantic is exclusively set by the mixing ratio of LNADW and Antarctic Bottom Water (AABW). Upper North Atlantic Deep Water (UNADW), in contrast, is characterized by εNd signatures between −12.7 and − 12.0 between 2°N and 10°N, whereas further north it is clearly affected by admixture of Mediterranean Water (MW) and radiogenic inputs from the Canary Islands and likely also the Cape Verde Islands. This article is part of a special issue entitled: Conway GEOTRACES - edited by Tim M. Conway, Tristan Horner, Yves Plancherel, and Aridane G. González.

Description: Highlights • Increased glacial sedimentation rates do not generate sufficient overpressure to trigger a landslide. • Simulated overpressures for different sedimentation scenarios do not significantly differ. • A glacimarine layer underneath rapidly-deposited sediments is important for overpressure build-up. • An earthquake of M6.9 or larger at a short distance from the Tampen Slide headwall could have triggered the Tampen Slide. Abstract Trough mouth fans are environments characterized by high sediment supply during glacial stages and the occurrence of large-scale instabilities. The geological record indicates that several of these environments have failed repeatedly resulting in large submarine landslides. The roles of sedimentation rate, weak layers, glacial loading and unloading as well as seismic activity on triggering megaslides in trough-mouth-fan systems is still unclear. A better understanding of the preconditioning factors, triggers and consequences of these landslides is crucial due to the hazard they pose to coastal communities and offshore industries. In this paper, we focus on the North Sea Trough Mouth Fan, which is the result of massive glacial sediment input delivered to the shelf edge through the Norwegian Channel, southeast Nordic Seas margin. The Tampen Slide, one of several large paleo-landslides that have happened within the North Sea Trough Mouth Fan, took place at c. 130 ka (end of MIS 6), and removed an estimated 1800 km3 of sediment. Here, we use boundary conditions from the Tampen Slide and 2D Finite Element Modeling (Abaqus software from Simulia) to evaluate the effects of variations in sedimentation rates as well as sediment properties on the generation of excess pore pressure, fluid flow, and slope stability along the axis of the trough-mouth-fan system. The model domain, 40 km in length and 2 km in height, is dominated by glacigenic debris flows and glacimarine sediment deposits. We use geotechnical data measured on samples of glacigenic and glacimarine sediment deposits from the nearby Ormen Lange gas field area to constrain the model. We evaluate the stability of the slope under various scenarios, including constant sediment loading, episodic changes in sedimentation rates and abrupt pulses in sediment delivery for a 61 kyr period (MIS 6). The models show that increased sedimentation rates during glacial stages do not generate sufficient excess pore pressure to set off a landslide. Furthermore, the simulated overpressures for the different sedimentation scenarios do not significantly differ at the end of the model runs. The results also highlight the importance of a basal glacimarine sediment layer underneath the rapidly-deposited sediments for the build-up of overpressure. Consequently, this glacimarine sediment layer has the inherited potential to act as a weak layer facilitating instability. However, as overpressure due to sediment deposition alone does not result in slope failure, we couple the preconditioned slope with earthquake ground shaking. Based on attenuation models, an earthquake of approximately M6.9 or larger at a short distance from the Tampen Slide headwall could have triggered the landslide. Therefore, we suggest glacial sedimentation and a glacimarine sediment layer to represent preconditioning factors, and seismic shaking as the final trigger mechanism for the Tampen Slide, i.e. similar to the situation that lead to the development of the Storegga Slide in the same area.

Description: The major processes that determine the distribution of methane (CH4) in anoxic marine sediments are methanogenesis and the anaerobic oxidation of methane (AOM), with organoclastic sulfate reduction exerting an important secondary control. However, the factors leading to the distribution of stable carbon isotopes (δ13C) of CH4 are currently poorly understood, in particular the commonly-observed minimum in δ13C-CH4 at the sulfate-methane transition (SMT) where AOM rates reach maximum values. Conventional isotope systematics predict 13C-enrichment of CH4 in the SMT due to preferential 12CH4 consumption by AOM. Two hypotheses put forward to explain this discrepancy are the addition of 12C-enriched CH4 to porewaters by methanogenesis in close proximity to AOM, and enzymatically-mediated carbon isotope equilibrium between forward and backward AOM at low concentrations of sulfate. To examine this in more detail, field data including δ13C of CH4 and dissolved inorganic carbon (DIC) from the continental margin offshore southwestern Taiwan were simulated with a reaction-transport model. Model simulations showed that the minima in δ13C-CH4 and δ13C-DIC in the SMT could only be simulated with carbon isotope equilibrium during AOM. The potential for carbon cycling between methanogenesis and AOM in and just below the SMT was insignificant due to very low rates of methanogenesis. Backward AOM also gives rise to a pronounced kink in the δ13C-DIC profile several meters below the SMT that has been observed in previous studies. We suggest that this kink marks the true base of the SMT where forward and backward AOM are operating at very low rates, possibly sustained by cryptic sulfur cycling or barite dissolution.

Description: Highlights • The pre-dill assessment of seismic data yielded identification of total 22 gas hydrate prospective sites. • The paper details the pre-expedition studies for identification of 18 Gas hydrate prospects. • On-board dynamic review studies for delineation of pre-expedition sites also detailed. • The drilling results matched with pre-expedition prediction, validated approach adopted for gas hydrate prospecting. Abstract After completing the first expedition of India's National Gas Hydrate Program (NGHP-01) in 2006, it was concluded that for the next expedition (National Gas Hydrate Program 02; NGHP-02), a new drill site review effort should focus on identifying potential deep-water offshore gas hydrate accumulations in sand dominated depositional environments. Therefore, geological and geophysical data analysis and 3D seismic data interpretation along with associated seismic modeling were carried out in three areas of the Krishna-Godavari Basin: Areas B, C, and E. Conventional petroleum exploration approaches of seismic amplitude evaluation were adapted to prospect for potentially sand-rich depositional systems within the gas hydrate stability zone. Subsequently, these prospective areas were further assessed through the geological and geophysical evaluation of depositional setting, gas sources, and gas migration pathways. In Area B, prospecting focused on a large anticlinal structure with a prominent bottom-simulating reflector and several key horizons that indicated evidence for potential sand-hosted hydrate occurrences. In Area C, the prospects were distributed throughout various settings within a very large deep-water channel-levee-fan system with complex indications of potential gas hydrate occurrence in sand-prone seismic facies. In Area E, prospects were associated with high amplitude events within inferred channel-levee sequences. Based on the pre-expedition/onboard drill-site evaluation, the 22 most promising sites in the Krishna-Godavari Basin were identified and prioritized to investigate and delineate a total of 17 identified gas hydrate prospects. This paper describes the geo-scientific studies carried out prior to NGHP-02 for site identification, evaluation and prioritization. An important outcome of this study is the identification of two potentially producible gas hydrate systems inferred to host significant quantities of gas hydrate in stratigraphic-structural traps.

Description: Highlights • Seafloor geomorphology was important in the structuring of abyssal megafauna. • Differences in megafaunal community ecology were found between all landscape types. • Lower megafauna density & diversity in a bathymetric valley than flat and ridge areas. • Large samples, collected by AUV, were required to make robust ecological conclusions. The potential for imminent polymetallic nodule mining in the Clarion Clipperton Fracture Zone (CCZ) has attracted considerable scientific and public attention. This concern stems from both the extremely large seafloor areas that may be impacted by mining, and the very limited knowledge of the fauna and ecology of this region. The environmental factors regulating seafloor ecology are still very poorly understood. In this study, we focus on megafaunal ecology in the proposed conservation zone ‘Area of Particular Environmental Interest 6′ (study area centred 17°16′N, 122°55′W). We employ bathymetric data to objectively define three landscape types in the area (a level bottom Flat, an elevated Ridge, a depressed Trough; water depth 3950–4250 m) that are characteristic of the wider CCZ. We use direct seabed sampling to characterise the sedimentary environment in each landscape, detecting no statistically significant differences in particle size distributions or organic matter content. Additional seafloor characteristics and data on both the metazoan and xenophyophore components of the megafauna were derived by extensive photographic survey from an autonomous underwater vehicle. Image data revealed that there were statistically significant differences in seafloor cover by nodules and in the occurrence of other hard substrata habitat between landscapes. Statistically significant differences in megafauna standing stock, functional structuring, diversity, and faunal composition were detected between landscapes. The Flat and Ridge areas exhibited a significantly higher standing stock and a distinct assemblage composition compared to the Trough. Geomorphological variations, presumably regulating local bottom water flows and the occurrence of nodule and xenophyophore test substrata, between study areas may be the mechanism driving these assemblage differences. We also used these data to assess the influence of sampling unit size on the estimation of ecological parameters. We discuss these results in the contexts of regional benthic ecology and the appropriate management of potential mining activities in the CCZ and elsewhere in the deep ocean.

Description: Highlights • Deglacial chemical weathering monitored by adsorbed isotopic and elemental signals • Resilience of authigenic geochemical signals towards variable lake redox conditions • Pronounced early deglacial weathering of labile accessory minerals • Remarkably congruent uranogenic and reduced thorogenic Pb isotope release • Anthropogenic, atmospherically deposited Pb pollution since over 2000 years Abstract Radiogenic Pb and Nd isotopes are well established tools in paleoceanographic science tracing ambient climate and continental runoff to the oceans down to sub-millennial timescales. Particularly in case of Pb isotopes, a clear climate dependency of continental isotopic runoff on glacial-interglacial transitions has been observed. Pb isotopes were reported to be released incongruently during initial chemical weathering. This incongruent release implies that Pb isotopic runoff compositions differ from the bulk catchment Pb isotopic signal. Yet only little is known about the processes leading to the incongruent release and the timescales of weathering on the continents. In this study we targeted the adsorbed trace metal signature in sediments from a Swiss high-Alpine lake that have accumulated since the retreat of the large Alpine ice domes during the last deglaciation to investigate initial Pb and Nd isotope weathering processes in a granitic environment. Additionally, selected adsorbed element concentrations and ratios were analysed to complement the isotopic physico-chemical weathering information. The integrity of the presented isotope records is supported by further investigation into the lake environment (e.g. oxic/anoxic conditions) and its potential influence on the isotopic record. The Pb isotope records during the early lake phase witnessed high-amplitude isotopic fluctuations linked to the initial chemical weathering of fine glacial substrate. This finding is also supported by the lithology of the core and rapidly decreasing adsorbed Th and U concentrations. Following this early lake phase, the majority of the Holocene traced congruent release of 207Pb/204Pb and 206Pb/204Pb and a significant depletion of 208Pb/204Pb in the adsorbed phase. These findings corroborate earlier suggestions of more effective weathering of uranogenic minerals yet also call for the presence of more weathering-resistant thorogenic minerals in the lake catchment. The latest 2.2 ka of the record are significantly overprinted by anthropogenic Pb deposition coinciding with the rise and fall of the Roman Empire. Finally, our data suggest that Nd isotopes are equally affected by incongruent weathering during the initial deglacial weathering processes, albeit at smaller magnitude than seen for Pb isotopes.

Description: CO2-induced ocean acidification and associated decrease of seawater carbonate saturation state contributed to multiple environmental crises in Earth’s history, and currently poses a major threat for marine calcifying organisms. Owing to their high abundance and good preservation in the Phanerozoic geological record, brachiopods present an advantageous taxon of marine calcifiers for palaeo-proxy applications as well as studies on biological mechanism to cope with environmental change. To investigate the geochemical and physiological responses of brachiopods to prolonged low-pH conditions we cultured Magellania venosa, Terebratella dorsata and Pajaudina atlantica under controlled experimental settings over a period of more than two years. Our experiments demonstrate that brachiopods form their calcite shells under strong biological control, which enables them to survive and grow under low-pH conditions and even in seawater strongly undersaturated with respect to calcite (pH = 7.35, Ωcal = 0.6). Using boron isotope (δ11B) systematics including MC-ICP-MS as well as SIMS analyses, validated against in vivo microelectrode measurements, we show that this resilience is achieved by strict regulation of the calcifying fluid pH between the epithelial mantle and the shell. We provide a culture-based δ11B−pH calibration, which as a result of the internal pH regulatory mechanisms deviates from the inorganic borate ion to pH relationship, but confirms a clear yet subtle pH dependency for brachiopods. At a micro-scale level, the incorporation of 11B appears to be principally driven by a physiological gradient across the shell, where the δ11B values of the innermost calcite record the internal calcifying fluid pH while the composition of the outermost layers is also influenced by seawater pH. These findings are of consequence to studies on biomineralisation processes, physiological adaptations as well as past climate reconstructions.

Description: Ecological studies need experimentation to test concepts and to disentangle causality in community dynamics. While simple models have given substantial insights into population and community dynamics, recent ecological concepts become increasingly complex. The globally important pelagic food web dynamics are well suited to test complex ecological concepts. For instance, trophic switches of individual organisms within pelagic food webs can elongate food webs or shift the balance between autotroph and heterotroph carbon fluxes. Here, we summarize results from mesocosm experiments demonstrating how environmental drivers result in trophic switches of marine phytoplankton and zooplankton communities. Such mesocosm experiments are useful to develop and test complex ecological concepts going beyond trophic level–based analyses, including diversity, individual behavior, and environmental stochasticity

Description: Highlights: • Researcher Ridge, a chain of volcanic seamounts in the central Atlantic is identified as a classical hotspot track; • The underlying small mantle plume is believed to get captured by the westward migrating Mid-Atlantic Ridge; • The bathymetric/geochemical anomaly of the Mid-Atlantic-Ridge at 14° N can therefore be explained by plume-ridge interaction. Abstract: Researcher Ridge is a 400 km long, WNW-ESE oriented chain of volcanic structures, located on ~20 to 40 Ma old oceanic crust on the western flank of the Mid-Atlantic Ridge (MAR) at ~15° N. Researcher Ridge has been little studied, and its age and origin are currently unclear. At roughly the same latitude (14–15° N), the MAR axis is bathymetrically elevated and geochemically enriched (hereafter referred to as the 14° N MAR anomaly). This study presents 40Ar/39Ar age data, major and trace elements, and Sr-Nd-Pb-Hf isotopic compositions of volcanic rocks dredged from several seamounts of the Researcher Ridge. In addition, new geochemical data of MORBs from two 13–14° N dredge sites on the MAR are also presented. The results reveal that Researcher Ridge lavas have geochemically enriched ocean island basalt compositions (chondrite-normalized [La/Sm]N = 1.7–5.0, and [Ce/Yb]N = 1.58–11.3) with isotopic signatures (143Nd/144Nd = 0.51294–0.51316, 87Sr/86Sr = 0.70266–0.70405, 206Pb/204Pb = 19.14–19.93, 207Pb/204Pb = 15.57–15.63, 208Pb/204Pb = 38.82–39.17, and 176Hf/177Hf = 0.28307–0.28312) trending towards the FOZO or HIMU mantle end member composition. Based on the new age and geochemical data, Researcher Ridge is interpreted as a classic hotspot track, albeit formed by a relatively weak melting anomaly. The lavas from the 14° N MAR anomaly have an enriched E-MORB type composition ([La/Sm]N = 1.81–2.29, [Ce/Yb]N = 1.6–3.9). Their isotopic compositions (143Nd/144Nd = 0.51298–0.51313, 87Sr/86Sr = 0.70250–0.70282, 206Pb/204Pb = 18.90–19.31, 207Pb/204Pb = 15.52–15.58, 208Pb/204Pb = 38.45–38.95, 176Hf/177Hf = 0.28315–0.28320) plot at the enriched end of the local MORB array and partly overlap the Researcher Ridge lava compositions, suggesting a genetic relationship. We propose that the 14° N MAR anomaly is caused by deflection of upwelling Researcher Ridge plume material towards the westward migrating MAR, causing the production of E-MORBs with similar isotopic compositions to the Researcher Ridge lavas. Once the plume was captured by the spreading ridge, off-axis hotspot track volcanism ceased, resulting in a seamount gap between the eastern end of the Researcher Ridge and the 14° N MAR anomaly.

Description: Temperature is a major factor that modulates the development and reactivity of the immune system. Only limited knowledge exists regarding the immune system of the catadromous European eel, Anguilla anguilla, especially during the oceanic early life history stages. Thus, a new molecular toolbox was developed, involving tissue specific characterisation of 3 housekeeping genes, 9 genes from the innate and 3 genes from the adaptive immune system of this species. The spatial pattern of immune genes reflected their function, e.g. complement component c3 was mainly produced in liver and il10 in the head kidney. Subsequently, the ontogeny of the immune system was studied in larvae reared from hatch to first-feeding at four temperatures, spanning their thermal tolerance range (16, 18, 20, and 22 °C). Expression of some genes (c3 and igm) declined post hatch, whilst expression of most other genes (mhc2, tlr2, il1β, irf3, irf7) increased with larval age. At the optimal temperature, 18 °C, this pattern of immune-gene expression revealed an immunocompromised phase between hatch (0 dph) and teeth-development (8 dph). The expression of two of the studied genes (mhc2, lysc) was temperature dependent, leading to increased mRNA levels at 22 °C. Additionally, at the lower end of the thermal spectrum (16 °C) immune competency appeared reduced, whilst close to the upper thermal limit (22 °C) larvae showed signs of thermal stress. Thus, protection against pathogens is probably impaired at temperatures close to the critical thermal maximum (CTmax), impacting survival and productivity in hatcheries and natural recruitment.

Description: Highlights • Records of hard-bottom communities show regional differences in community dynamics. • Regionally, signs of regime shift were detected. • Shift can be explained by the decline of the foundation species Mytilus sp. • Modelling process revealed three environmental variables explaining the decline. • Regional differences in larval dispersal could explain contrary Mytilus recoveries. Abstract Ecological processes modulate ecosystem functioning and services. Foundation species are those exerting intense control on such processes as both their existence and loss have profound implications on the structure of ecological communities. For the distinction between random fluctuations and directional regime shifts in community composition, long-term records are of strategic need. In this study we present the monitoring of benthic hard-bottom communities over 11 years along seven stations in the SW Baltic Sea. Regional differences were found between the communities of Kiel and Lübeck bights, with the former area displaying signs of regime shift. The decline and near disappearance of the foundational species Mytilus edulis from settlement panels deployed in Kiel Bight correlated with three environmental variables: sea surface temperature, water current speed and chlorophyll a concentration. Thus, low spring temperatures, in some cases reinforced by local maxima of chlorophyll a, correlated with reduced recruitment of Mytilus. Moreover, regional differences of larval dispersal and population connectivity could explain the rapid recovery after disturbance of the mussel populations in Lübeck Bight in contrast to Kiel Bight. Our findings underscore the relevance of long-term monitoring programmes to detect the interactive impacts of global climatic and regional environmental drivers.

Description: Highlights • Seasonal variations in air-sea CO2 fluxes on the Great Barrier Reef reveal a strong CO2 release during the early-dry season. • The Great Barrier Reef is overall a net source of CO2. • CO2 fluxes are largely controlled by cross-shelf advection of oversaturated warm surface waters from the Coral Sea. Abstract The Great Barrier Reef (GBR) is the largest contiguous coral reef system in the world. Carbonate chemistry studies and flux quantification within the GBR have largely focused on reef calcification and dissolution, with relatively little work on shelf-scale CO2 dynamics. In this manuscript, we describe the shelf-scale seasonal variability in inorganic carbon and air-sea CO2 fluxes over the main seasons (wet summer, early dry and late dry seasons) in the GBR. Our large-scale dataset reveals that despite spatial-temporal variations, the GBR as a whole is a net source of CO2 to the atmosphere, with calculated air–sea fluxes varying between −6.19 and 12.17 mmol m−2 d−1 (average ± standard error: 1.44 ± 0.15 mmol m−2 d−1), with the strongest release of CO2 occurring during the wet season. The release of CO2 to the atmosphere is likely controlled by mixing of Coral Sea surface water, typically oversaturated in CO2, with the warm shelf waters of the GBR. This leads to oversaturation of the GBR system relative to the atmosphere and a consequent net CO2 release.

Description: This paper is based on the results of a comprehensive investigations of sediments from seven cores sampled during the International Russian-Chinese Cruise 53 of the R/V “Akademik Lavrentyev” (2010) in the frames of the Russian-Chinese collaboration between the Pacific Oceanological Institute of the Far-Eastern Branch of the Russian Academy of Sciences (POI FEB RAS, Vladivostok, Russia), and the First Institute of Oceanography (FIO, Qingdao, China). Baitoushan (Chanbaishan) Volcano had several powerful explosive eruptions during the Middle Pleistocene-Holocene, which produced widespread tephra layers. The paper reports chemical composition of volcanic glasses and minerals from six tephra layers labeled as B-Og, B-Sado, B-J, B-Un1, B-V, and B-Tm, which belong to Baitoushan Volcano and were identified in sediments of the northwestern part of the Sea of Japan. The tephras were dated using geochronological data for the host sediments. The estimated ages for the Middle Pleistocene tephra is 488 ka; the Late Pleistocene tephras are 71.1–71.9 cal. kа (B-Sado), 50.8 cal. ka (B-J), 38.3 cal. ka (B-Un1), and 29.0–29.4 cal. ka (B-V). The ash layers consist of alkali-rich glass of trachydacitic to alkaline rhyolitic composition and specific assemblage of minerals including Fe-rich augite-hedenbergite, aegirine-augite, aegirine, arfvedsonite, and fayalite. The mineral assemblage is typical for alkalic volcanic rocks from continental rift setting. Aenigmatite, a rare mineral from the group of inosilicates, was firstly identified in distal tephra of Baitoushan Volcano, supplied into marine sediments. The composition of glasses and minerals from all layers are similar. It testifies about steady-state conditions of the magma accumulation under Baitoushan Volcano and about the bimodal character of magmatic chambers during the Late Pleistocene and Holocene (since 100 ka).

Description: In order to gain knowledge about the potential effects of acidification in aquatic ecosystems, global change research based on microalgae as sentinel species has been often developed. However, these studies are limited to single species tests and there is still a research gap about the behaviour of microalgal communities under this environmental stressor. Thus, the aim of this study was to assess the negative effects of CO2 under an ecologically realistic scenario. To achieve this objective, two types of toxicity tests were developed; i) single toxicity tests and ii) multispecies toxicity tests, in order to evaluate the effects on each species as well as the interspecific competition. For this purpose, three microalgae species (Tetraselmis chuii, Phaeodactylum tricornutum and Nannochloropsis gaditana) were exposed to two selected pH levels (7.4, 6.0) and a control (pH 8.0). The pH values were choosen for testing different scenarios of CO2 enrichment including the exchange atmosphere-ocean (pH 7.4) and natural or anthropogenic sources of CO2 (pH 6.0). The effects on growth, cell viability, oxidative stress, plus inherent cell properties (size, complexity and autofluorescence) were studied using flow cytometry (FCM). Results showed that T. chuii was the most resistant species to CO2 enrichment with less abrupt changes in terms of cell density, inherent cell properties, oxidative stress and cell viability. Although P. tricornutum was the dominant species in both single and multispecies tests, this species showed the highest decrease in cell density under pH 6.0. Effects of competence were recorded in the multispecies control (pH 8) but this competence was eclipsed by the effects of low pH. The knowledge of biological interactions made by different microalgae species is a useful tool to extrapolate research data from laboratory to the field.

Description: Highlights • At least parts of the Beata Ridge formed during the main CLIP stage at 95–83 Ma. • Sampling of numerous volcanic rocks indicates a broad extrusive magmatic event. • Depleted and enriched geochemical signatures point to a heterogeneous mantle source. • Geochemical heterogeneities can occur on a small scale of tens of kilometers. Abstract The Caribbean Large Igneous Province (CLIP), a Cretaceous oceanic flood basalt province, presumably formed at the initiation of the Galápagos hotspot. During the M81 cruise of the German R/V METEOR, we sampled the Beata Ridge, a prominent submarine structure in the Caribbean Sea belonging to the CLIP. The ridge offers the opportunity to directly sample basement sequences of the central, submarine part of the CLIP, complementing numerous studies of accreted CLIP sequences exposed on land around the margins of this LIP. The majority of the recovered Beata Ridge samples are volcanic, implying that at least parts of the Beata Ridge were formed during a large extrusive event in contrast to previous assumptions that the structure is primarily composed of intrusive rocks. Several stratigraphically controlled profiles were sampled along the western slope of the Beata Ridge using the remotely operated vehicle (ROV) Kiel 6000 and revealed variously alternating sequences of magmatic rocks (lavas, pillow breccias, tuffs and gabbros) and sediment plains. We report new 40Ar/39Ar age and geochemical (major and trace element, Sr-Nd-Hf-Pb isotope) data for the recovered magmatic samples. Although the 40Ar/39Ar analyses display disturbed age spectra, they suggest an age range of 92.4–76.9 Ma. Thus our age data show for the first time that the Beata Ridge also formed during the main magmatic stage of the CLIP (~95–83 Ma). Previous studies suggested that the Beata Ridge was formed during a second, lower-volume magmatic phase of the CLIP (~81–71 Ma), possibly related to decompression melting during an extensional phase in the Caribbean. Most samples display relatively flat chondrite-normalized rare earth element (REE) patterns commonly observed throughout the CLIP, but light REE enriched and depleted compositions are also present. The occurrence of enriched and depleted incompatible element and radiogenic isotope signatures implies a heterogeneous mantle source region, as is observed for other LIPs worldwide. Since a high degree of geochemical variability is observed over short stratigraphic intervals within the ROV profiles, melt homogenization did not operate as effectively as commonly assumed for LIPs. Instead the plume head probably preserved some domains of enriched and depleted components, whereas most of the melts during the main stage have intermediate compositions (with flat REE patterns), representing mixtures of the enriched and depleted components.

Description: Highlights • Exposure ages that constrain ice sheet thickness collated from an online database. • Thinning rates are reconstructed from 23 sites across Antarctica. • Palaeo-thinning rates are comparable to modern observations. • Wide-spread thinning during the Holocene, but after Meltwater Pulse 1A. Abstract Constraining Antarctic ice sheet evolution provides a way to validate numerical ice sheet models that aid predictions of sea-level rise. In this paper we collate cosmogenic exposure ages from exposed nunataks in Antarctica that have been used, or have the potential to be used, to constrain rates of thinning of the Antarctic Ice Sheets since the Last Glacial Maximum. We undertake quality control of the data and adopt a Bayesian approach to outlier detection. Past thinning rates are modelled by Monte Carlo linear regression analysis. We present thinning rates from 23 sites across Antarctica. The resulting data set is the first Antarctic-wide collation of past ice sheet thinning rates and provides an empirical starting point for future model-data comparisons. Palaeo-thinning rates are spatially variable with high rates appearing to correlate to areas of contemporary rapid changes. On centennial timescales past thinning rates are comparable to modern day observations implying that modern day thinning has the potential to persist for centuries in numerous parts of Antarctica. The onset of abrupt thinning from all sites post-dates Meltwater Pulse 1A suggesting that its source region(s) are distal to areas where exposure age constraints on ice surface geometry exist.

Description: Highlights • Robust increase in silt size at 5 ka reflects increased flow of Labrador Sea Water. • Ice-rafted debris likely affects on the Labrador Slope during the last deglacial. • End member modeling and corrections provide insight into deglacial sediments. Abstract The Labrador Sea is a vital region for the Atlantic Meridional Overturning Circulation (AMOC), where overflow waters from the Nordic Seas mix with locally produced Labrador Sea Water (LSW), before exiting to the interior of the Atlantic Ocean. The dynamical sedimentary proxy of mean sortable silt size ( ) can give information on past changes in deep water circulation speed and the strength of AMOC. We have produced records from two core sites at depths between 1500 and 2000 m on the continental slope east of Newfoundland, to reconstruct changes in intermediate depth water circulation speed, including Glacial North Atlantic Intermediate Water and Labrador Sea Water over the past 22,000 years. Increases in appear to coincide with much of the deglaciation as well as the mid-late Holocene. End-member modeling suggests that ice-rafted debris (IRD) is an important factor in interpreting during the deglaciation. We find that a robust increase in is likely unrelated to IRD during the past 5 ka, and probably reflects increased flow at intermediate depths due to local production of LSW strengthening as Nordic Seas overflows weakened at this depth. Our results highlight both the complications of producing records in IRD-rich, slope environments and the promise that this proxy nevertheless has for reconstructing dynamical changes in deep ocean currents.

Description: Global warming is already affecting the oceans through changes in water temperature, acidification, oxygen content and sea level rise, amongst many others. These changes are having multiple effects on marine species worldwide, with subsequent impacts on marine fisheries, peoples' livelihoods and food security. This work presents a review of the recent literature on the current and projected impacts of climate change on Canada's Pacific marine ecosystem. We find that there is an increasing number of studies in British Columbia focusing on changes in ocean conditions and marine species responses under climate change, including an emerging literature on the socio-economic impacts of these changes considered to be a knowledge gap. According to the literature, it is well established that ocean temperatures are increasing over the long-term, especially, in southern areas of British Columbia. Warming trends are increasing in the spring and are strongest in summer. However, there are important uncertainties regarding other climate drivers, such as oxygen concentration and acidification, stemming mainly from the insufficiency of data. Pacific salmon, elasmobranchs, invertebrates and rockfishes are amongst the most vulnerable species groups to climate change in British Columbia. Also, shifts in stock distribution and fish abundance under climate change may have a significant impact on fish supply affecting the livelihoods and food security of some British Columbians. The magnitude of these impacts is likely to vary according to a latitudinal gradient, with southern coastal areas being more affected than northern and central areas; challenging multiple areas of governance, such as equity and fishing access amongst First Nations; and institutional arrangements for transboundary stocks between the U.S. and Canada.

Description: We assessed the potential of Calcium (Ca) isotope fractionation measurements in blood (δ44/42CaBlood) and urine (δ44/42CaUrine) as a new biomarker for the diagnosis of osteoporosis. One hundred post-menopausal women aged 50 to 75 years underwent dual-energy X-ray absorptiometry (DXA), the gold standard for determination of bone mineral density. After exclusion of women with kidney failure and vitamin D deficiency (〈25 nmol/l) 80 women remained in the study. Of these women 14 fulfilled the standard diagnostic criteria for osteoporosis based on DXA. Both the δ44/42CaBlood (p 〈 0.001) and δ44/42CaUrine (p = 0.004) values were significantly different in women with osteoporosis (δ44/42CaBlood: −0.99 ± 0.10‰, δ 44/42CaUrine: +0.10 ± 0.21‰, (Mean ± one standard deviation (SD) n = 14) from those without osteoporosis (δ44/42CaBlood: −0.84 ± 0.14‰, δ44/42CaUrine: +0.35 ± 0.33‰, (SD), n = 66). This corresponded to the average Ca concentrations in morning spot urine samples ([Ca]Urine) which were higher (p = 0.041) in those women suffering from osteoporosis ([Ca]Urine-Osteoporosis: 2.58 ± 1.26 mmol/l, (SD), n = 14) than in the control group ([Ca]Urine-Control: 1.96 ± 1.39 mmol/l, (SD), n = 66). However, blood Ca concentrations were statistically indistinguishable between groups ([Ca]Blood, control: 2.39 ± 0.10 mmol/l (SD), n = 66); osteoporosis group: 2.43 ± 0.10 mmol/l (SD, n = 14) and were also not correlated to their corresponding Ca isotope compositions. The δ44/42CaBlood and δ44/42CaUrine values correlated significantly (p = 0.004 to p = 0.031) with their corresponding DXA data indicating that both Ca isotope ratios are biomarkers for osteoporosis. Furthermore, Ca isotope ratios were significantly correlated to other clinical parameters ([Ca]Urine, ([Ca]Urine/Creatinine)) and biomarkers (CRP, CTX/P1NP) associated with bone mineralization and demineralization. From regression analysis it can be shown that the δ44/42CaBlood values are the best biomarker for osteoporosis and that no other clinical parameters need to be taken into account in order to improve diagnosis. Cut-off values for discrimination of subjects suffering from osteoporosis were − 0.85‰ and 0.16‰ for δ44/42CaBlood and δ44/42CaUrine, respectively. Corresponding sensitivities were 100% for δ44/42CaBlood and ~79% for δ44/42CaUrine. Apparent specificities were ~55% for δ44/42CaBlood and ~71%. The apparent discrepancy in the number of diagnosed cases is reconciled by the different methodological approaches to diagnose osteoporosis. DXA reflects the bone mass density (BMD) of selected bones only (femur and spine) whereas the Ca isotope biomarker reflects bone Ca loss of the whole skeleton. In addition, the close correlation between Ca isotopes and biomarkers of bone demineralization suggest that early changes in bone demineralization are detected by Ca isotope values, long before radiological changes in BMD can manifest on DXA. Further studies are required to independently confirm that Ca isotope measurement provide a sensitive, non-invasive and radiation-free method for the diagnosis of osteoporosis.

Description: The composition of the growth medium has a major influence on the physiological properties of microalgae. We have previously shown that addition of the trace elements Zn and I enhances desiccation-induced fluorescence quenching (q des ) in the lichen phycobiont Trebouxia asymmetrica. q des is likely to be an important factor of the tolerance against drought, as it has a protective function against photoinhibition in the dehydrated state of this poikilohydric organism. The influence of the presence of iodine and/or zinc ions in culture media on growth of T. asymmetrica and its ability to show q des were investigated. T. asymmetrica was able to grow in seawater and showed enhanced q des as compared to when grown in the usual Bold's basal growth medium. While artificial seawater had no effect, addition of Zn and I in the concentrations present in natural seawater enhanced q des to almost the same level as observed in natural seawater. The presence of Zn and I also increased growth by the factor of almost 2, thus approximating the growth rate reached in enriched seawater. Both effects, enhancement of q des and of the growth rate were dependent on the simultaneous presence of both elements. Adding only one element at any concentration resulted in no or very little effect on either growth rate or q des . The mechanism of the action of both elements is unknown. It is possible that the simultaneous presence of I and Zn has a profound effect on the fitness of lichens containing T. asymmetrica in nature.