The spring mesozooplankton variability and its relationship with hydrobiological structure over year-to-year changes (2003–2013) in the southern Bay of Biscay (Northeast Atlantic)

International audienceMesozooplankton can be considered the most important secondary producers in marine food webs because they hold an intermediate position between the phytoplankton assemblage and the upper trophic levels. They also are a robust indicator of climatic and hydrological conditions. We conducted an analysis of the interannual variability of the spring mesozooplankton assemblage, as sampled by the PELGAS fisheries survey in the southern part of the Bay of Biscay (Northeast Atlantic Ocean) between 2003 and 2013. We examined hydrology and trophic drivers to explain the variability. Our results revealed that the subsurface temperature, the subsurface salinity, the biomasses of subsurface pico-, nano-, and microphytoplankton, and the copepod assemblage exhibited a recurrent spatial pattern that was driven mainly by freshwater and nutrient inputs from the main rivers. The mesozooplankton assemblage was dominated by copepods (82%), composed of coastal, neritic, and oceanic copepod genera that paralleled the various hydrological fronts converging in the southern Bay of Biscay. The copepod community displayed high temporal-variability; there were three periods of abundant adult copepods throughout the southern Bay of Biscay. The copepod community was structured primarily around the drive for resource control, especially by the microphytoplankton biomass (24.3% of the total variability), and to a lesser extent by hydrological features (13.7% of the total variability)

PHYTOBS dataset - French National Service of Observation for Phytoplankton in coastal waters

The PHYTOBS dataset includes long-term time series on marine microphytoplankton, since 1987, along the whole French metropolitan coast. Microphytoplankton data cover microscopic taxonomic identifications and counts. The whole dataset is available, it includes 25 sampling locations.PHYTOBS network studies microphytoplankton diversity in the hydrological context along French coasts under gradients of anthropogenic pressures. PHYTOBS network allows to analyse the responses of phytoplankton communities to environmental changes, to assess the quality of the coastal environment through indicators, to define ecological niches, to detect variations in bloom phenology, and to support any scientific question by providing data.The PHYTOBS network provides the scientific community and stakeholders with validated and qualified data, in order to improve knowledge regarding biomass, abundance and composition of marine microphytoplankton in coastal and lagoon waters in their hydrological context.PHYTOBS originates of two networks. The historical REPHY (French Observation and Monitoring program for Phytoplankton and Hydrology in coastal waters) supported by Ifremer since 1984 and the SOMLIT (Service d'observation en milieu littoral) supported by INSU-CNRS since 1995. The monitoring has started in 1987 on some sites and later in others.Hydrological data are provided by REPHY or SOMLIT network as a function of site locations