Monitoring fresh and brackish water quality around shellfish farming areas with a bivalve embryo and larva simplified bioassay method

The standard bivalve embryos-larval bioassay method has been modified for monitoring the water quality in an important mussel culture area, La Rochelle Bay. Fertilised eggs from naturally spawned Mytilus galloprovincialis mussels were incubated for 48 h at 18 ± 1 degree C, in different water samples (five replicates) from the bay and its surroundings. The mean percentages of abnormalities, with the 95 % confidence limit, of controls and different water samples were compared. The method was shown to allow the application of the the bioassay to fresh, brackish and marine waters. The assessment of the water quality of the different tributaries to the Bay and that of freshwaters from intensively cultivated marshes close to it, showed that it varied form toxic to lethal, according to Woelke's classification. In contrast, the seawater of the mussel culture area was unpolluted.