The West Gironde Mud Patch (WGMP) is a 420-km2 mud belt in the Bay of Biscay, located 25 km off the mouth of the Gironde estuary. This clay-silt feature of 4 m in thickness extends between 30 and 75m water depth, surrounded by the sands and gravels that cover the North Aquitaine continental shelf. Interface cores were collected during JERICOBent-1 cruise (October 2016; Deflandre (2016) doi.org/10.17600/16010400) along two cross-shelf transects for a total of 9 sites. Each sediment core was carefully extruded every 0.5 cm from the top core to 4 cm and every 1 cm below until the core bottom. The sediment layers were used to determine dry bulk density, grain size and selected radioisotope activities (210Pb, 226Ra, 137Cs, 228Th, K).

The aim of this work was to document the seasonal and inter-annual dynamic of dissolved oxygen and ancillary data (T, S, Chl-a, turbidity, pH) along a cross-shelf transect off the Gironde estuary. This work has been motivated by recent simulations that suggest the occurrence of seasonal bottom deoxygenations in this River-dominated Ocean Margin (Riomar); but unfortunately there were no data sets to test this hypothesis until now. Profiles of temperature, salinity and dissolved oxygen were performed in the water column of the West Gironde Mud Patch off the Gironde estuary (from 45°46.383’N – 1°28.925’W to 45°35.524’N - 1°50.689’W) during seven cruises on the R/V Côte de la Manche (doi: 10.18142/284 ; 10.17600/18000861) between 2016 and 2021 (October 2016, August 2017, January 2018, April 2018, July 2019, April 2021, October 2021). Turbidity was measured in January and April 2018, July 2019 and October 2021, Chl-a in October 2016, August 2017, January 2018, April 2018 and July 2019 and pH in October 2021. This dataset had permitted to validate the occurrence of bottom deoxygenations when the water column is stratified.

A spatialized EwE model was built covering the continental shelf of the Bay of Biscay. From this base, six ECOPATH models were built: a current model serving as a reference, a model only including the effect of climate change on native species, and four models also simulating the arrival of NIS under different hypotheses of biomass. These models include 44 native trophic groups ranging from primary production to top predators, including 13 monospecific groups of commercial interest, and two non-living groups. In addition, 8 non-indigenous trophic groups and 11 fishing fleets have been integrated in order to model the main professions operating today in the Bay of Biscay