L.M. Dionisio Pires

Influence of toxic and non-toxic phytoplankton on feeding and survival of Dreissena polymorpha (Pallas) larvae

Grazing and survival of larvae of the zebra mussel, Dreissena polymorpha, on a green alga and cyanobacteria were studied in laboratory experiments. Clearance rates of the larvae were determined for Chlamydomonas reinhardtii (green alga), two non-toxic and two toxic Microcystis aeruginosa strains (Cyanobacteria). Clearance rates of larvae on non-toxic Microcystis were significantly higher than on toxic Microcystis. The clearance rate on Chlamydomonas reinhardtii was in between the clearance rates on toxic and non-toxic Microcystis strains and not significantly different from them. Effects of toxicity of Microcystis on the survival of zebra mussel larvae was investigated in a short-term experiment. Survival of larvae fed toxic Microcystis was lower than that of larvae fed non-toxic Microcystis, but higher than that of starved larvae. This may imply that, for survival of zebra mussel larvae, it is better to have bad quality (toxic) food than no food.