Pelagos Expedition

Study of the conditions that influence species distribution (physicochemical parameters and plankton)

Twenty sampling points for various parameters (temperature, salinity, plankton) were established along a radial line between Calvi and Nice.

The structure of the water column is determined by physical and chemical parameters in the Ligurian Sea. It is noteworthy that the distribution of maximum phytoplankton biomass coincides with that of zooplankton and, above all, with 70% of the diversity of megafauna species observed at sea, including certain bioindicators of productive zones, such as the sunfish, the sea turtle, and the fin whale.

The sandy seabed begins at the sandy beaches along the coast and extends down to great depths. This habitat, which covers many square kilometers of the Mediterranean coastline, is home to a teeming, unique, and strange marine life—yet one that remains poorly understood.
These sandy habitats are often considered, in comparison to Posidonia seagrass beds or coralligenous ecosystems, to be “poor” habitats, and frequently as environments “to be sacrificed” for the location of a discharge point, a dredging area, a development project, or to direct the mooring of recreational vessels. Furthermore, they account for the vast majority of offshore development projects and are therefore the habitat most impacted by the expansion of human activities (Holon et al., 2015), particularly coastal land reclamation.

During the project, 48 dives were conducted in 11 survey areas across 3 sites (fine sand, Bastia; sandy-mud, between Nice and Antibes; near seagrass beds or rocks, Saint-Florent). The combination of the diurnal cycle, depth, substrate type, and nearby biocoenoses allows for the identification of 7 typical communities within the infralittoral soft-bottom habitats.

Exploration of this little-known habitat has revealed the presence of rare species (such as the white grouper and the angel fish) and numerous juveniles, highlighting the importance of this ecological niche.

Megafauna observation campaigns have made it possible to collect data and document a rich diversity of pelagic megafauna, with more than 400 observations recorded. The eight most common species of marine mammals in the sanctuary were observed, including the fin whale and Cuvier’s beaked whale.

Many species of birds were observed, including migratory species such as the northern gannet, the razorbill, and the Atlantic puffin. Other species, such as the loggerhead sea turtle, bluefin tuna, and schools of devilfish, were also frequently observed.

These campaigns also helped document the threats and impacts of human activities, such as pollution, bycatch, and maritime traffic.