Cyanobacterial toxins have not originally evolved as defence
mechanism against grazing, because the toxins are ancient
However, co-evolution has shaped phytoplankton
and their grazers and today cyanobacterial hepatotoxins
may act also as defence mechanisms
Abiotic factors, such as nutrients, salinity, temperature and light
and their effect on cyanobacteria toxin production have been more
thoroughly studied in the laboratory
whereas the ecological role of microcystin production is still
largely unknown as are the biotic conditions
that promote toxin production.