The bay of Villefranche-sur-Mer (French Riviera) is a medium-sized bay (2 miles long by 0.8 wide) characterized by great depth (> 300 m at its mouth) and the absence of a continental shelf. It is sheltered from the prevailing east and west winds This oligotrophic to mesotrophic site is located in a highly urbanized area, subjected to seasonal anthropogenic influences: cruise ships, intense yachts traffic, increases of population. The Roya (26 km E), Paillon (4 km W) and Var (30 km W) rivers are the closest freshwater inflows, with strong seasonal variability. This sampling site is exceptional in that, thanks to the absence of a continental shelf and the northerly current, oceanic organisms (e.g. gelatinous organisms) reach the coast via the offshore water masses that enter the bay. This privileged location has enabled a unique hydrological monitoring service to set up at a fixed station (Point B; 43°41.00N/7°.19.000E; 80 m depth) near the Institut de la Mer in Villefranche-sur-Mer (IMEV) since 1957, and providing year-round temporal coverage with weekly sampling intervals.

Weekly samplings are conducted either at two (1 and 50m) or six (1, 10, 20, 30, 40, 50, 75 m) sampling depths. A multi-parameter autonomous profiler is deployed at each sampling time for the whole water column, and at each sampling depth, water samples are analyzed for a panel of biochemical oceanographic parameters (temperature, salinity, nutrients, pH, isotopes, suspended matter, COP, NOP, chlorophyll a biomass; cytometry since 2009).

In addition to sampling at Point B, to characterize the regional autumn-winter mixing layer and winter water mass, weekly profiles of bio-physical parameters (temperatures, salinity, fluorescence, dissolved oxygen) at Point B+ (43°41.00N/7°18.000E; 150 m) and at Point C (43°40.550N/7°18.600E; 300 m depth), are carried out on the same day as Point B, if weather permitting. Parallel to the biogeochemical monitoring, zooplankton and microphytoplankton samples (as part of the PHYTOBS and REPHY networks) are taken, allowing us to follow the fluctuations of the communities at the multi-decadal scale. High-frequency monitoring (COAST HF) of temperature, salinity and fluorescence measurements is also carried out from the autonomous EOL platform located a few tens of meters from Point B. Thus, we have an original series of more than 60 years of biological, physical and chemical variables at the same sampling point.

All these monitorings, carried out on the station boat with her staff, are provided by the observation staff of the IMEV with a contribution of staff from the Laboratory of Oceanology of Villefranche (LOV).