Monitoring of a Potential Harmful Algal Species in the Berre Lagoon by Automated In Situ Flow Cytometry

Abstract

The vicinity of urban activity and industry (petrochemistry) around the Berre lagoon (southeast of France) has induced the degradation of its ecosystem, characterized by a permanent eutrophic state. In particular, a power plant has discharged substantial inputs of enriched freshwater in the lagoon since 1966. Due to these high nutrient inputs and also to regeneration rates, several species of phytoplankton regularly bloom in the lagoon at spring, summer, or autumn. Peaks of phytoplanktonic biomass (>150 µg Chl a /dm 3 ) are generally followed by intense heterotrophic activities leading to O 2 consumption with hypoxic or anoxic episodes. The study of phytoplankton dynamics is thus of primary importance.Within the framework of an ecological survey, an automated platform of in situ instruments was set up in a laboratory located on the "Berre l'Etang" harbor to assess biological and hydrological features of the lagoon at short time scale during October 2011. The phytoplanktonic community was characterized by a Cytosense autonomous fl ow cytometer (Cytobuoy, Netherlands) operating at high frequency (hourly sampling) in order to detect sudden changes of species compositions and abundances. In parallel, hydrological sensors have measured several physicochemical variables of the water directly pumped from the lagoon (1.5 m depth) to the fi eld laboratory.In October 2011, among the various phytoplanktonic species optically resolved by the Cytosense, the dinofl agellate Akashiwo sanguinea has

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