The Arcachon Bay is a unique and ecologically important meso-tidal lagoon on the Atlantic coast of south-west France. The Arcachon Bay has the largest area of dwarf seagrass (Z. noltei) in Europe, the extent of which was stable in their extent between the 1950s and 1990s, but a decline in seagrass was observed in mid-2000. The decline of Zostera (seagrass) may have a significant impact on sedimentation in this coastal ecosystem rich in marine life. Interface cores were collected in September 2022 to determine sediment and mass accumulation rates (SAR, MAR) in the Arcachon Bay. Ten study areas were selected, distributed over most of the areas where seagrass meadows are actually observed. Two sites were visited each time, one with the presence of Zostera noltei in good condition (Healthy) and the other where the sediment was bare (Bare). Maximum water heights during spring tides range from 3.44 m for the deepest site (Garrèche) to 2.09 m for the shallowest site (Fontaines). A total of 20 sediment cores were sampled and carefully extruded every 1 cm from the top to the bottom of the core. The sediment layers were used to determine dry bulk density and selected radioisotope activities: DBD, 210Pb, 226Ra, 137Cs, 228Th and 40K expressed as %K). 

Tracking data of 7 grey seals were obtained from the deployment of Fastloc GPS/GSM tags developed by the Sea Mammal Research Unit (UK). Full tag description is available at: http://www.smru.st-andrews.ac.uk/Instrumentation/GPSPhoneTag/. The tags include a wet-dry sensor from which haulout events are recorded, a pressure sensor providing detailed dive data, as well as a Fastloc GPS recording irregular locations when the seal is not underwater. Data is stored onboard and transmitted via the GSM network when the seal is in the reception range. The data provided here are the individual GPS locations of the seals fitted with these tags for an average duration of 135 days.

The dataset includes age- and length-based catch per unit effort data for commercial fish species collected by the French trawl survey EVHOE.

The Pélagiques Gascogne (PELGAS, Doray et al., 2000) integrated survey aims at assessing the biomass of small pelagic fish and monitoring and studying the dynamics and diversity of the Bay of Biscay pelagic ecosystem in springtime. PELGAS has been conducted within the EU Common Fisheries Policy Data Collection Framework and Ifremer’s Fisheries Information System. Details on survey protocols and data processing methodologies can be found in Doray et al., (2014, 2018a). This dataset comprises the biomass (in metric tons) and abundance (in thousands of individuals) of small pelagic fish estimated during the PELGAS survey in the Bay of Biscay in springtime. The dataset also includes the estimation coefficient of variation, derived based on the hydroacoustic methodology described in Doray et al. (2010), and the survey area. Those estimates have been validated by the ICES WGACEGG group and provided to the ICES WGHANSA group for stock assessment purposes. Data have been used in Doray et al., 2018b.

As part of the marine water quality monitoring of the “Pertuis” and the “baie de l’Aiguillon” (France), commissioned by the OFB and carried out by setec énergie environnement, three monitoring stations were installed. Two of them were set up at the mouths of the Charente and Seudre rivers on February 6 and 27, 2019, respectively, while a third was deployed in the Bay of Aiguillon on March 24, 2021. The dataset presented here concerns the station installed in the Charente estuary. Measurements are organized into .csv files, with one file per year. Data is collected using a SAMBAT multiparameter probe, which records the following parameters: - Temperature (-5 to 35 °C) - Conductivity (0 to 10 mS/cm) - Pressure (0 to 10 m) - Turbidity (0 to 300 NTU) - Dissolved Oxygen (0 to 20 mg/L & 0 to 200 %) - Fluorescence (0 to 50 µg/l) - PH (0/14)

The SOMLIT-Antioche observation station, located at 5 nautical miles from Chef de Baie harbor (La Rochelle) is part of the French monitoring network SOMLIT (https://www.somlit.fr/), accredited by the INSU-CNRS as a national Earth Science Observatory (Service National d’Observation : SNO), which comprises 12 observation stations distributed throughout France in coastal locations. It aims to detect long-term changes  of these ecosystems under both natural and anthropogenic forcings. SOMLIT is part of the national research infrastructure for coastal ocean observation ILICO (https://www.ir-ilico.fr/?PagePrincipale&lang=en). The SOMLIT-Antioche station (46.0842 °N, 1.30833 °W) is located in the north-eastern part of the Bay of Biscay, halfway between the islands of Ré and Oléron, at the centre of what is commonly known as the Pertuis Charentais area, which correspond to a semi-enclosed shallow basin and includes four islands (Ré, Oléron, Aix and Madame) and three Pertuis (i.e., detroit) (Breton, Antioche and Maumusson). This 40m-deep site, with muddy to sandy marine bottoms, is submitted to a macro-tidal regime and is largely open to the prevailing westerly swells. It remains under a dominant oceanic/neritic influence, even though its winter/spring hydrological context is influenced by the diluted plumes of the Charente, Gironde and Loire rivers, but not by those of too small estuaries (Lay, Seudre and Sèvre Niortaise). SOMLIT-Antioche hydrological monitoring has been carried out by the LIENSs/OASU laboratory on a fortnightly basis since June 2011. Surface water samples are collected  at high-tide during intermediate tides (70 ± 10 in SHOM units) on board the research  vessel ‘L’Estran’ owned by La Rochelle University. Samples are analyzed for more than 16 core parameters: temperature, salinity, dissolved oxygen, pH, ammonia, nitrates, nitrites, phosphates, silicates, suspended matter, particulate organic carbone, particulate organic nitrogen, chlorophyll, delta15N, delta13C; pico- and nano- plankton. Measurements are carried out in accordance with the ISO/IEC 17025:2017 standard. Simultaneous monitoring of the micro-phytoplankton community (since 2013, SNO PHYTOBS: https://www.phytobs.fr/en) and monitoring of prokaryotic communities (Bacteria and Archaea) are also carried out on a monthly basis. Since 2019, seasonal observations of benthic invertebrate communities (SNO BenthObs : https://www.benthobs.fr/) have also been carried out. This monitoring is complementary to that carried out at hydrological stations in the pre-existing REPHY and DCE networks, some of which are located near marine farming areas (oyster and mussel farms).

Mesoscale dynamics in the Mediterranean Sea have been investigated for years and anticyclonic eddies are regularly observed features in the Algerian Basin. In early spring 2016, a field experiment during the ProtevsMed 2016 cruise thoroughly investigated this specific eddy, when it was located near the North Balearic Front, taking high-resolution (Seasoar) hydrological transects, several CTD casts and LADCP measurements. In addition, four drifting buoys were released in the eddy core. These in situ measurements revealed that the vertical structure of this anticyclone was made of two water lenses of very different origins (Atlantic Water above and Western Intermediate Water below) spinning together. In the vicinity of the North Balearic Front, which may act as a dynamical barrier for structures, the eddy interacted with a subsurface anticyclonic eddy made of modal water, which fostered cross-front exchanges generating filaments by stirring. The high-resolution sampling revealed fine scales structures both adjacent to the eddy and within its core. The eddy has been targeted from 21 March to 1 April 2016 taking advantage of a meteorological window. It has been sampled with:  - a towed undulating vehicle, the SeaSoar designed and built by Chelsea Instruments; it gets mounted on its sides two Sea-bird SBE-9 (SBE 3 temperature and SBE 4 conductivity sensors)  and a Wetlabs Fluorometer of type ChloroA WetStar  - CTD casts performed with a Sea-bird SBE-9 (SBE 3 temperature and SBE 4 conductivity sensor) and an RDI 150 kHz current profiler mounted in a general oceanics 12-place rosette, with12l Niskin bottles  - drifters with holey-sock positioned at 50 m deep below the expected Ekman layer thickness (remaining in the eddy until mid May).

The Pélagiques Gascogne (PELGAS, Doray et al., 2000) integrated survey aims at assessing the biomass of small pelagic fish and monitoring and studying the dynamics and diversity of the Bay of Biscay pelagic ecosystem in springtime. PELGAS has been conducted within the EU Common Fisheries Policy Data Collection Framework and Ifremer’s Fisheries Information System. Details on survey protocols and data processing methodologies can be found in Doray et al., (2014, 2018). This dataset comprises the abundance (no. of individuals), biomass (metric tons), mean length (cm), mean weight (g) of marine organisms collected by midwater trawling to identify fish echoes detected during PELGAS surveys (2000-2018). All parameters have been raised to the trawl haul level. Trawl haul metadata and species reference list are also provided.

This dataset gather isotopic ratios (carbon and nitrogen) and concentrations of mercury species (methyl and inorganic mercury) measured in several tissues (muscle, liver and gonad) for three commonly consumed fish species from the south Bay of Biscay (France) in 2017 and 2018.

This database contains hauls collated from 1965 to 2019, from fisheries dependent and independent data, from across eastern Atlantic waters and French Mediterranean waters. From this data diadromous fish spatio-temporal data was cleaned and standardised.