• European Marine Science
• French National Research Agency (ANR) close

Climate warming and related drivers of soil thermal change in the Arctic are expected to modify the distribution and dynamics of carbon contained in perennially frozen grounds. Thawing of permafrost in the Mackenzie Delta region of northwestern Canada, coupled with increases in river discharge and coastal erosion, trigger the release of terrestrial organic matter (OMt) from the largest Arctic drainage basin in North America into the Arctic Ocean. While this process is ongoing, well-established, and its rate is accelerating, the fate of the newly-mobilized organic matter, as it transits from the watershed through the delta and into the marine system, remains poorly understood. In the framework of the European Horizon 2020 Nunataryuk programme, and as part of the Work Package 4 (WP4) Coastal Waters theme, four field expeditions were conducted in the Mackenzie Delta region and southern Beaufort Sea from April to September 2019. The temporal sampling design allowed the survey of ambient conditions in the coastal waters under full ice cover prior to the spring freshet, during ice break-up in summer, as well as anterior to the freeze-up period in fall. To capture the fluvial-marine transition zone, and with distinct challenges related to shallow waters and changing seasonal and meteorological conditions, the field sampling was conducted in close partnership with members of the communities of Aklavik, Inuvik and Tuktoyaktuk, using several platforms: helicopters, snowmobiles and small boats. Water column profiles of physical and optical variables were measured in situ, while surface water, groundwater and sediment samples were collected and preserved for the determination of the composition and sources of OMt, including particulate and dissolved organic carbon (POC, DOC), and chromophoric dissolved organic matter (CDOM), as well as a suite of physical, chemical and biological variables. Here we present an overview of the standardized datasets, including hydrographic profiles, remote sensing reflectance, temperature and salinity, particle absorption, nutrients, dissolved organic carbon, particulate organic carbon, particulate organic nitrogen, colored dissolved organic matter absorption, fluorescent dissolved organic matter intensity, suspended particulate matter, total particulate carbon, total particulate nitrogen, stable water isotopes, radon in water, bacterial abundance, and a string of phytoplankton pigments including total chlorophyll. Datasets and related metadata can be found in Juhls et al. 2021. https://doi.pangaea.de/10.1594/PANGAEA.937587.

The stable isotope composition of dissolved silicon in seawater (δ30SiDSi) was examined at 10 stations along the GEOVIDE section (GEOTRACES GA-01), spanning the North Atlantic Ocean (40–60° N) and Labrador Sea. Variations in δ30SiDSi below 500 m were closely tied to the distribution of water masses. Higher δ30SiDSi values are associated with intermediate and deep water masses of northern Atlantic or Arctic Ocean origin, whilst lower δ30SiDSi values are associated with DSi-rich waters sourced ultimately from the Southern Ocean. Correspondingly, the lowest δ30SiDSi values were observed in the deep and abyssal eastern North Atlantic, where dense southern-sourced waters dominate. The extent to which the spreading of water masses influences the δ30SiDSi distribution is marked clearly by Labrador Sea Water (LSW), whose high δ30SiDSi signature is visible not only within its region of formation within the Labrador and Irminger seas, but also throughout the mid-depth western and eastern North Atlantic Ocean. Both δ30SiDSi and hydrographic parameters document the circulation of LSW into the eastern North Atlantic, where it overlies southern-sourced Lower Deep Water. The GEOVIDE δ30SiDSi distribution thus provides a clear view of the direct interaction between subpolar/polar water masses of northern and southern origin, and allow examination of the extent to which these far-field signals influence the local δ30SiDSi distribution.

International audience; The conservation of biodiversity-and the vital ecosystem services it generates-is one of the greatest challenges humanity faces, yet the field faces drastic funding cuts as society realigns its priorities in the face of the COVID-19 pandemic. Here, we argue that diverting attention from conservation would, however, increase the risk of further global health crises because the emergence of novel infectious diseases is partially driven by global environmental change. As the discrepancy between conservation needs and society's willingness to pay for them grows, conservation will have to evolve to stay relevant in the age global change-induced human infectious disease.

Tara Oceans particularly acknowledges the commitment of the following sponsors: the CNRS (in particular Groupement de Recherche GDR3280), the European Molecular Biology Laboratory, Genoscope/CEA, French Government “Investissements d’Avenir” programs OCEANOMICS (ANR-11-BTBR-0008) and FRANCE GENOMIQUE (ANR-10-INBS-09-08), Agence Nationale de la Recherche, and European Union FP7 (Micro B3 no. 287589). We appreciate the support and commitment of agnès b. and E. Bourgois, Veolia Environment Foundation, Region Bretagne, Lorient Agglomeration, World Courier, Illumina, Eléctricité de France Foundation, Fondation pour la recherche sur la biodiversité, Prince Albert II de Monaco Foundation, Tara Foundation, its schooner, and its teams. We are also grateful to the French Ministry of Foreign Affairs for supporting the expedition and to the countries that granted sampling permissions. Tara Oceans would not exist without continuous support from 23 institutes (http://oceans.taraexpeditions.org/en/m/science/les-labos-impliques/). This article is contribution number 52 of Tara Oceans. This study is funded by Tara Oceans and the Malaspina 2010 Expedition project (Spanish Ministry of Economy and Competitiveness, CSD2008-00077) and has received additional support from the King Abdullah University of Science and Technology through baseline funding to X.I. and C.M.D., Campus de Excelencia Internacional del Mar (CEIMAR), and PLASTREND (BBVA Foundation) and MIDaS (CTM2016-77106-R, AEI/FEDER/UE) projects. The subtropical ocean gyres are recognized as great marine accummulation zones of floating plastic debris; however, the possibility of plastic accumulation at polar latitudes has been overlooked because of the lack of nearby pollution sources. In the present study, the Arctic Ocean was extensively sampled for floating plastic debris from the Tara Oceans circumpolar expedition. Although plastic debris was scarce or absent in most of the Arctic waters, it reached high concentrations (hundreds of thousands of pieces per square kilometer) in the northernmost and easternmost areas of the Greenland and Barents seas. The fragmentation and typology of the plastic suggested an abundant presence of aged debris that originated from distant sources. This hypothesis was corroborated by the relatively high ratios of marine surface plastic to local pollution sources. Surface circulation models and field data showed that the poleward branch of the Thermohaline Circulation transfers floating debris from the North Atlantic to the Greenland and Barents seas, which would be a dead end for this plastic conveyor belt. Given the limited surface transport of the plastic that accumulated here and the mechanisms acting for the downward transport, the seafloor beneath this Arctic sector is hypothesized as an important sink of plastic debris. Peer reviewed

International audience; Near-shore and direct groundwater inputs are frequently omitted from nutrient budgets of coastal lagoons. This study investigated groundwater-driven dissolved inorganic nitrogen (DIN) inputs from an alluvial aquifer to the hypertrophic Or lagoon, with a focus on the Salaison River. Piezometric contours revealed that the Salaison hydrogeological catchment is 42% bigger than the surface watershed and hydraulic gradients suggest significant groundwater discharge all along the stream. Hydrograph separation of the water flow at a gauging station located 3 km upstream from the Or lagoon combined with DIN historical data enabled to estimate that groundwater-driven DIN inputs account for 81–87% of the annual total DIN inputs to the stream upstream from the gauging station. A radon mass balance was performed for the hydrological cycle 2017–2018 to estimate groundwater inflow into the downstream part of the stream. Results showed that (1) DIN fluxes increased by a factor 1.1 to 2.3 between the gauging station and the Salaison outlet, (2) the increase in DIN was due to two groundwater-fed canals and to groundwater discharge along the stream, the latter represented 63–78% of the water flow. This study thus highlights the significance of groundwater driven DIN inputs into the Salaison River, which account for 90% of the annual DIN inputs. This is particularly true in the downstream part of the river, which, on averages, supplies 48% of total DIN inputs to the river. These downstream DIN inputs into the Or lagoon were previously not taken into account in the management of this and other Mediterranean lagoons. The inputs will probably affect restoration processes for many years due to their residence time in the aquifer. This study throws light on a rarely documented source of ‘very-nearshore’ groundwater discharge to coastal streams in water and nutrient budgets of coastal zone ecosystems.

International audience; Bacteria of the Vibrio genus are the most predominant infectious agents threatening marine wildlife and aquaculture. Due to the large genetic diversity of these pathogens, the molecular determinants of Vibrio virulence are only poorly understood. Furthermore, studies tend to ignore co-evolutionary interactions between different host populations and their locally encountered Vibrio communities. Here, we explore the molecular targets of such co-evolutionary interactions by analyzing the genomes of nine Vibrio strains from the Splendidus-clade showing opposite virulence patterns towards two populations of Pacific oysters introduced into European Wadden Sea. By contrasting Vibrio phylogeny to their host specific virulence patterns, we could identify two core genome genes (OG1907 and OG 3159) that determine the genotype by genotype (G × G) interactions between oyster larvae and their sympatric Vibrio communities. Both genes show positive selection between locations targeting only few amino acid positions. Deletion of each gene led to a loss of the host specific virulence patterns while complementation with OG3159 alleles from both locations could recreate the wild type phenotypes matching the origin of the allele. This indicates that both genes can act as a genetic switch for Vibrio-oyster coevolution demonstrating that local adaptation in distinct Vibrio lineages can rely on only few genes independent of larger pathogenicity islands or plasmids.

Abstract Women are less likely to enroll in selective or scientific courses, applying for promotions and are particularly underrepresented in both middle and top positions in the STEM field. Quota are often advocated as an instrument to reduce this gender gap, but it remains unclear at what step of the career ladder they more effectively foster women's reaching the top. Many factors may affect quota's success or failure, such as how they would in turn affect teamwork and trust between members within organizations or coordination in applying for promotions. In this paper, by means of a laboratory experiment implementing a two-stage tournament, we evaluate the impact of three different interventions in affecting individual decision to climb the career ladder, abstracting away from other possible confounding factors. We find that, compared with no intervention, a gender quota introduced in the initial stage of competition was ineffective in encouraging women to compete for the top; quotas introduced in the final stage of competition or at both stages increased women's willingness to compete for the top, without distorting the performance of the winners.