The role of microcystins in heavy cyanobacterial bloom formation

The presence of high microcystin concentrations in cyanobacterial blooms additionally affects species diversity. Blooms with high toxin contents can reach higher cell densities, which is also demonstrated by microcystin cell contents. In vitro experiments show that microcystins influence phytoplankton proliferation. The action is strongly dependent on the phytoplankten species tested and light conditions. We propose that the environmental impact of different microcystins depends on their enzymatic inhibition activity and thus could not be measured merely on the basis of their toxicity to vertebrate species. Their role in heavy cyanobacterial bloom and scum formation is discussed, as well as their impact on the massive proliferation of other species following toxic cyanobacterial bloom degradation.