Is the meiofauna a good indicator for climate change and anthropogenic impacts?

Our planet is changing, and one of the most pressing challenges facing the scientific community revolves around understanding how ecological communities respond to global changes. From coastal to deep-sea ecosystems, ecologists are exploring new areas of research to find model organisms that help predict the future of life on our planet. Among the different categories of organisms, meiofauna offer several advantages for the study of marine benthic ecosystems. This paper reviews the advances in the study of meiofauna with regard to climate change and anthropogenic impacts. Four taxonomic groups are valuable for predicting global changes: foraminifers (especially calcareous forms), nematodes, copepods and ostracods. Environmental variables are fundamental in the interpretation of meiofaunal patterns and multistressor experiments are more informative than single stressor ones, revealing complex ecological and biological interactions. Global change has a general negative effect on meiofauna, with important consequences on benthic food webs. However, some meiofaunal species can be favoured by the extreme conditions induced by global change, as they can exhibit remarkable physiological adaptations. This review highlights the need to incorporate studies on taxonomy, genetics and function of meiofaunal taxa into global change impact research

Population dynamics of modern planktonic foraminifera in the western Barents Sea

International audienceThis study reports on diversity and distribution of planktonic foraminifera (PF) in the Barents Sea Opening (BSO). Populations of PF living in late summer (collected by means of stratified plankton tows) and recently deposited individuals (sampled by interface corer) were compared. High abundances reaching up to 400 unit ind.m-3 in tow samples and 8000 unit ind.m-3 in surface sediments were recorded in the centre of the studied area while low abundances were observed in coastal areas, likely due to continental influences. The living and core-top assemblages are mainly composed of the same four species Neogloboquadrina pachyderma, Neogloboquadrina incompta, Turborotalita quinqueloba and Globigerinita uvula. The two species G. uvula and T. quinqueloba dominate the upper water column, whereas surface sediment assemblages display particularly high concentrations of N. pachyderma. The unusual dominance of G. uvula in the water sample assemblages compared to its low proportion in surface sediments might be the signature of (1) a seasonal signal due to summer phytoplankton composition changes at the BSO, linked to the increase in summer temperature at the study site, and/or (2) a signal of a larger timescale and wider geographical reach phenomenon reflecting poleward temperate/subpolar species migration and consecutive foraminiferal assemblage diversification at high latitudes due to global change. Protein concentrations were measured on single specimens and used as a proxy of individual carbon biomass. Specimens of all species show the same trend, a northward decrease in their size-normalized-protein concentration. This suggests that foraminiferal biomass is potentially controlled by different constituents of their organelles (e.g. lipids). The coupling of data from plankton tows, protein measurements and surface sediments allows us to hypothesize that PF dynamics (seasonality and distribution) are decoupled from their metabolism

Contribution du compartiment sédimentaire à la demande en oxygène dissous durant un évènement hypoxique dans l'estuaire de la Loire (France)

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Prospection du lit mineur et des berges sur le site médiéval de Taillebourg - Port-d’Envaux (Charente-Maritime) : un secteur d’activité lié à la Charente

The village of Taillebourg is situated on the right bank of the Charente river about 40 km from the Atlantic Ocean. On the opposite bank is the village of Port-d’Envaux, in the alluvial plain which forms the main channel of the Charente. Tide influence can be seen as far as Taillebourg and beyond : this phenomenon, combined with a strong currant at this point of the river, allowed certain types of sea faring boats to come upriver, thus favorising port activities. The medieval port site at Taillebourg – Port-d’Envaux has revealed numerous remains dating primarily from the VIIth and Xth centuries. Fifteen logboats, three wrecks, structural remains including a late IXth century dyke, as well as numerous objects (pottery, weapons, tools) are all conserved at a depth of 8 m along a succession of three shallows. Subaquatic prospecting revealed three objects, the identities of which are definitely scandinavian (two axes and a ring) and other objects (leads and an anchor) which are probably of scandinavian origin. In addition, amongst the abundant archaeological finds collected from the river, there are objects, particulary arms, which correspond chronologically with the period of the viking raids (IXth century) but which are not of clear scandinavian origin and could equally correspond to the local population. A geophysical survey was performed on the banks adjoining the site. The aim was to find potential remains of a settlement of the banks that could be linked with fittings of the river’s bed. A magnetic cartography, completed with electromagnetic data (Slingram method), was realized with a caesium vapor magnetometer on 13 000 m2. No structure can’t be highlight with assurance ; however, in boundaries of the map appear some parallel and parpendicular linear anomalies with probably anthropic origin.Les prospections subaquatiques menées sur le site portuaire médiéval de Taillebourg – Port-d’Envaux (situé à environ 40 km de l’Océan Atlantique), ont livré de nombreux vestiges datés entre les VIIe et Xe siècles ; pirogues monoxyles, épaves assemblées, vestiges structurés et objets variés (céramiques, armes, outils) sont répartis sur ou aux abords de trois hauts-fonds. Le corpus comprend également des éléments qui trouvent des comparaisons typologiques et stylistiques dans l’Europe du Nord ainsi que des productions qui correspondent à l’époque des raids vikings (IXe siècle) mais qui peuvent aussi bien être associées aux populations locales qu’aux vikings. Une prospection géophysique conduite sur les berges a mis en évidence des anomalies linéaires dont l’origine anthropique et la relation avec l’aménagement du lit du fleuve sont probables.Mariotti Jean-François, Dumont Annie, Mathé Vivien, Camus Adrien, Lévêque François, Jaubert Anne Nissen, Hulot Olivia, Greck Sandra, Szepertyski Béatrice. Prospection du lit mineur et des berges sur le site médiéval de Taillebourg - Port-d’Envaux (Charente-Maritime) : un secteur d’activité lié à la Charente. In: Aquitania : une revue inter-régionale d'archéologie, tome 21, 2005. pp. 299-336

Early diagenetic processes in an eutrophic estuarine system: indices of sediment contribution to summer hypoxia of the Loire?

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Impact of an exceptional winter flood on benthic oxygen and nutrient fluxes in a temperate macrotidal estuary: Potential consequences on summer deoxygenation

Despite 20 years of control on eutrophication, episodes of summer hypoxia still occur in the Loire estuary, impacting water quality and posing a key scientific and management challenge. This work aimed to quantify the contribution of the benthic compartment to hypoxia in the Loire estuary by direct measurement of water–sediment fluxes and an in-depth understanding of the seasonal variations of oxides and phosphorus stocks. During the summer’s low-discharge period, results show that the iron oxide-rich deposit is stable under hypoxic conditions, limiting the release of dissolved phosphorus into the overlying water column. The high nitrate content of the water column appears to be an important oxidizer of iron during hypoxic periods, limiting dissolved phosphorus leakage and aggravation of hypoxia. During the exceptional winter flood, significant sediment erosion associated with bubbling phenomena (attributed to methane efflux) created severe fractures in the sediment and stimulated water–sediment exchange. During the following months, these fractures were progressively filled, which decreased the intensity of benthic fluxes. However, due to the high residence time in the water during the summer period, a simple model demonstrated that benthic contributions were sufficient to directly (by direct oxygen consumption) or indirectly (by promoting ammonia oxidation) affect the oxygen stock in the water column during the low-discharge period. Our study demonstrates the importance of the benthic compartment in the occurrence of hypoxia and the obvious lack of knowledge to illustrate and model the biogeochemical functioning of the estuary

A survey of the summer coccolithophore community in the western Barents Sea

International audienceThe Barents Sea is particularly vulnerable to large-scale hydro-climatic changes associated with the polar amplification of climate change. Key oceanographical variables in this region are the seasonal development of sea-ice and the location and strength of physico-chemical gradients in the surface and subsurface water layers induced by the convergence of Arctic-and Atlantic-derived water masses. Remote sensing imagery have highlighted the increasing success of calcifying haptophytes (coccolithophores) in the summer phytoplankton production of the Barents Sea over the last 20 years, as a response to an overall larger contribution of Atlantic waters to surface and sub-surface waters, as well as to enhanced sea-ice melt-induced summer stratification of the photic layer. The present study provides a first thorough description of coccolithophore standing stocks and diversity over the shelf and slope of the western Barents Sea from two sets of surface and water column samples collected during August-September 2014 from northern Norway to southern Svalbard. The abundance and composition of coccolithophore cells and skeletal remains (coccoliths) are discussed in view of the physical-chemical-biological status of the surface waters and water column based on in-situ (temperature, salinity, fluorescence) and shore-based (microscope enumerations, chemotaxonomy) measurements, as well as satellite-derived data (Chl a and particulate inorganic carbon contents). The coccolithophore population is characterized by a low species diversity and the overwhelming dominance of Emiliania huxleyi. Coccolithophores are abundant both within the well stratified, Norwegian coastal water-influenced shallow mixed layer off northern Norway, as well as within well-mixed cool Atlantic water in close vicinity of the Polar Front. Bloom concentrations with standing stocks larger than 4 million cells/l are recorded in the latter area north of 75°N. Our limited set of chemotaxonomic data suggests that coccolithophores contribute substantially (ca. 20% of the total Chl a) to the summer phytoplankton community which is made essentially of small-sized algal groups. Excluding the bloom area, coccolith calcite accounts for an average of 20% to the bulk particulate inorganic carbon content in the surface waters, and explains to some extent the satellite-derived spatial distribution of this parameter. Deep water living coccolithophore species thriving below the pycnocline as well as populations present in well-mixed cool Atlantic water are rapidly transferred to depth in the form of intact coccospheres down to at least 200 m. High amplitude internal waves which, according to our observations, affect a wide range of water depth up to the lower photic zone, might strengthen the vertical transfer of this sinking population

The risk of COVID-19 death is much greater and age dependent with type I IFN autoantibodies

International audienceSignificance There is growing evidence that preexisting autoantibodies neutralizing type I interferons (IFNs) are strong determinants of life-threatening COVID-19 pneumonia. It is important to estimate their quantitative impact on COVID-19 mortality upon SARS-CoV-2 infection, by age and sex, as both the prevalence of these autoantibodies and the risk of COVID-19 death increase with age and are higher in men. Using an unvaccinated sample of 1,261 deceased patients and 34,159 individuals from the general population, we found that autoantibodies against type I IFNs strongly increased the SARS-CoV-2 infection fatality rate at all ages, in both men and women. Autoantibodies against type I IFNs are strong and common predictors of life-threatening COVID-19. Testing for these autoantibodies should be considered in the general population