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We report the first occurrences of Spiophanes afer Meißner, 2005 and Prionospio cristaventralis Delgado-Blas, Díaz-Díaz & Viéitez, 2018 from French marine waters (from the southern part of the Bay of Biscay in NE Atlantic, and the Gulf of Lion in the Mediterranean Sea). Morphological characters of S. afer include the presence of an occipital antenna, dorsal ciliated organs extending to chaetigers 13–15, neuropodial hooks from chaetiger 15, ventrolateral intersegmental pouches from chaetigers 14–15, chaetal spreaders of “2+3 type”, and conspicuous dark brown pigmentation on parapodia of chaetigers 9–13. Prionospio cristaventralis has four pairs of branchiae (1st and 4th pinnate, 2nd and 3rd apinnate), ventral crests from chaetigers 11–12, high dorsal crests on chaetigers 10–11, and very large notopodial prechaetal lamellae on anterior chaetigers. Both records represent northern extensions of their known distributions. However, the presence of S. afer on French coasts may have been overlooked for several decades. The validity of the recently proposed Spiophanes adriaticus is questioned.

International audience; Chronic hypoxia and anoxia have strong impacts on coastal aquatic ecosystems worldwide. Such situations are essentially driven by high benthic oxygen (O2) demand resulting from organic matter mineralization in surface sediment and amplified by a low mixing of the water column. However, the benthic O2 demand may greatly vary according to the O2 availability, sediment biogeochemical properties, and bioturbation by macrobenthic fauna. Here we examined how the sediment O2 demand vary in response to seasonal and long-term (pluri-decadal) hypoxia in the Berre lagoon, a coastal ecosystem impacted by chronic hypoxia events since ca 60 years. Oxygen penetration depth, diffusive and total O2 fluxes were measured in situ using a microelectrode autonomous profiler and benthic chamber deployments at three sites impacted by quite-permanent (PA), seasonal (PI) and occasional (PO) hypoxia in August 2016. Those measurements were seasonally repeated at site PI between August 2015 and August 2016. Additional physical and chemical characteristics were also measured in surface sediment. Sediment profile images analysis combined to measures of benthic macrofaunal communities characteristics were determined in order to estimate the quality of the benthic ecosystem. The highest benthic O2 demand was observed after seasonal anoxia in relation to the important accumulation of reduced chemical species in surface sediment. Interestingly, both pluri-decadal hypoxia and normoxia produced relatively high benthic O2 demand related to a higher accumulation of organic matter and to the presence of reduced chemical species at site dominated by hypoxia, and to the presence of fresher organic matter and active bioturbating macrofaunal communities in normoxic site. The low benthic O2 demand at site seasonally impacted by hypoxia was explained by the degraded state of the macrofaunal community and by the lower accumulation of reduced chemical species. The occurrence of hypoxia and anoxia situations in the Berre lagoon was predicted from the competition between kinetics of benthic O2 demand and water column reoxygenation events induced by strong wind. The good correspondence between the measured and predicted hypoxia/anoxia occurrence clearly indicates that the chronic deoxygenation events in the Berre lagoon, and the associated degraded state of the benthic ecosystem are driven jointly by the benthic O2 demand and the intensity and duration of the water column stratification.

International audience; On the Bay of Biscay continental shelf, there are several mid-shelf mud patches including La Grande Vasière to the north, the West Gironde Mud Patch (WGMP) off the Gironde estuary and the Basque Mud Patch close to the Spanish border. In general, these deposits are several meters thick and cover coarser substrate. Questions remain about their storage capability for fine particles and carbon. This work investigates the sedimentation of the WGMP in order to develop a first estimate of organic carbon (OC) burial. Interface sediment cores were collected at nine stations along two cross-shelf transects in October-November 2016. X-radiograph imaging and grain-size analyses were used to characterize sedimentary structures. 210 Pb xs depth profiles were established to calculate sediment (SAR) and mass (MAR) accumulation rates. Sedimentary structures indicate episodic sandy inputs overlying older deposits at proximal sites, and relatively continuous sedimentation at seaward locations. On the outer-central portion of the northern transect, a maximum SAR (0.47 cm yr − 1) was observed, suggesting a depocenter. On the southern transect, excluding two stations where sedimentary inputs appear massive but sporadic, the SARs are lower (