The Bay of Bourgneuf, France, is a main site of
shellfish production. In the marshes along the bay, oyster intensive rearing
and fattening need the mass production of microalgae. Salt groundwaters,
available in this region, support a large part of this production for
aquaculture. Studies carried out by local authorities have brought to the
fore the accumulation of lead (Pb) in several samples of algal pastes
derived from cultures using salt groundwater. The aim of this study was to
compare growth, nutritional value and metal (Cd, Cu, Pb and Zn) uptake of
four microalgae grown in two salt groundwaters or in enriched coastal
seawater. Cultures of microalgae used in aquaculture (Haslea ostrearia, Phaeodactylum tricornutum, Skeletonema costatum and Tetraselmis suecica) were
realised at the laboratory under controlled experimental conditions. Results
indicated that salt groundwaters provided cultures with, at least, an equal
biomass and a nutritional value similar to cultures grown in enriched
seawater. There was no difference regarding metal accumulation whatever the
culture medium, except when S. costatum was grown in one of the salt groundwater in
which case its cadmium levels were higher and could be above the French
guideline level. These observations questioned on the bioavailability of
metals in salt groundwaters. It also underlines the specificity of metal
uptake and accumulation by microalgae.