Biological parameters: Chlorophyll (several algorithms), Particulate Organic/Inorganic Carbon, Fluorescence…

Measurements by drifting surface buoys. This system is a drifting mooring consisting of a surface buoy fastened to a floating anchor by a cable (trip line, buoy rope). It has to monitor as precisely as possible the water volume in which the floating anchor is immersed. The surface buoys are traced by Argos satellites.

This In Situ delayed mode product integrates the best available version of in situ oxygen, chlorophyll / fluorescence and nutrients data. The latest version of Copernicus delayed-mode BGC (bio-geo-chemical) product is also distributed from Copernicus Marine catalogue.

For the 21 years of the study, an examination of trends in chlorophyll concentration revealed a general decline throughout the Gulf over the production period. These trends, extracted from dynamic linear model, also allowed this decline to be quantified. Expressed as a percentage, a large part of the area below the 50 m bathymetric line showed a decrease of at least 10% over the period, corresponding to a value of at least 0.1 µg.l-1. However, the spatial distribution reveals some more local phenomena. In southern Brittany, from Quimper to Vannes, a particular feature appears, with an upward trend over several kilometres along the coast, followed by a pronounced gradient along the coast. This gradient includes a zone where a continuous monotonic increasing trend is observed, then a zone where the trend becomes not significant and finally, about 15 km from the coast, a new zone where a significant continuous monotonic decreasing trend is observed. The increase in chlorophyll a concentration in the very coastal part is greater than 0.1 µg.l-1 over the period. Another peculiarity concerns the central part, located at the edge of the plateau at Cap Ferrat and Pente Aquitaine, where an increase in chlorophyll a was observed, but the variations remained small, being less than 0.1 µg.l-1. About a hundred kilometres south-west of Saint Nazaire, an area of about 40 by 50 km shows a decrease in chlorophyll a of more than 20%, quantified as more than 0.1 µg.l-1 over the period.

Data collected by the Spindrift 2 Sails of Change vessel during its attempt at the round-the-world sailing record, the Jules Verne Trophy. More information at https://spindrift-racing.com/fr/.

The MAGEST observation network aims to continuously monitor the physico-chemical quality of the waters of the estuaries of Northern Aquitaine. In 2023, this regional network is composed of 12 stations.