COAST-HF-BESSète time series (French Research Infrastructure ILICO): long-term and high frequency core parameter monitoring of the water column in the continental shelf in front of Sète City, North-western Mediterranean Sea

The COAST-HF-BESSète station is a part of the French monitoring network COAST-HF (Coastal OceAn observing SysTem – High Frequency, http://coast-hf.fr/) accredited by the French Centre National de la Recherche Scientifique (CNRS) as a National Observatory System (SNO). The main objective aims to understand and analyze evolution at different temporal scales of the coastal environment, ranging from the dynamics of extreme or transient events developing at high frequency (hour, day) to multi-annual trends. The scientific issues at the heart of the objectives of COAST-HF and which find an echo in national and international strategies, are therefore part of the themes of the impact of climate change and anthropogenic pressures in coastal regions The BESSète station (latitude 43.3267N, longitude 3.66167E) is located in the dilution zone of a large river, the Rhône, but also small coastal rivers (Vène, Aude, Herault), especially those of the Thau lagoon basin. The BESSète station is monitored from the Station Méditerranéenne de l’Environnement Littoral (SMEL) of the University of Montpellier in Sète by the staff of the OSU OREME, and the Research Unities of MARBEC (http://www.umr-marbec.fr/en/) and GéoSciences (http://www.gm.univ-montp2.fr/?lang=en). The BESSète station, located on a water-column depth of 30 m, is made up of several probes fixed at 3 m depth on a Cardinal Buoy BFI (Immersed Float Buoy) made available by Phares et Balises. These probes record at high frequency, typically every 15 minutes, pressure (dbar), temperature (°C), salinity (psu), dissolved oxygen concentration (ml/l), turbidity (ntu) and Chla fluorescence (mg/m3). This station is complementary to another observation station, SOMLIT-Sète which samples at the water surface in a bi-monthly frequency these same parameters among a greater diversity of core parameters. A station of the SNO PHYTOBS (Phytoplankton observation network), PHYTOBS-Sète, is also complementary and located at the same location. The station is also a privileged site for the development of other observation networks such as BENTHOBS (https://www.benthobs.fr/) or scientific network projects such as the CocoriCO2 project (Petton et al, 2024). COAST-HF-BESète is part of the long-term coastal observation stations of the French Research Infrastructure dedicated to coastal ocean observations (Infrastructure de Recherche Littorale et Côtières: ILICO, https://www.ir-ilico.fr). The data are stored, validated and qualified in diffred time on the platform Coastal Coriolis (https://data.coriolis-cotier.org/).