ETUDE DES EFFLORESCENCES TOXIQUES A CYANOBACTERIES DANS LE BARRAGE MEXA, ALGERIE

The presence of the toxic cyanobacteria in water bodies used either for drinking or irrigation purposes may present serious health risks for the human population. In this context, Mexa dam in North-East of Algeria has been sampled for toxin-producing cyanobacteria and especially for the algae producing microcystins. Physicochemical and biological water quality, including intracellular microcystins concentrations was investigated for the first time, during ten months, from March to December 2007. Eight cyanobacterial genera were observed and five from them are toxin-producing cyanobacteria. Microcystis sp. is the predominant specie, on November and December reaching high cell densities of 2,101x106cell.ml-1. Intracellular microcystins concentrations in algal samples analyzed by immunological ELISA assay reached the highest value (0, 77 μg.l-1) on November. This toxin concentration was recorded where the highest chlorophyll-a concentrations and Microcystis sp. cell densities occurred.