Effects of dissolved microcystins on growth of planktonic photoautotrophs

Effects of cyanobacterial toxins microcystin-LR and -RR on growth of five representatives of Chlorophyta (Chlamydomonas reinhardtii, Chlorella kesslerii, Pediastrum duplex, Pseudokirchneriella subcapitata, Scenedesmus quadricauda) and cyanobacterium Microcystis aeruginosa (Cyanophyta) were investigated in the concentration range 1–25,000 μg l−1 using microplate assays (evaluated after 4, 7 and 11 days). Our results demostrate different susceptibility of several planktonic organisms to microcystins. In some species (C. reinhardtii, C. kesslerii, P. duplex, M. aeruginosa), microcystin-RR induced more pronounced effects on growth than structural variant microcystin-LR. However, environmentally relevant concentrations of microcystins (1–10 μg l−1) did not cause significant growth alterations. Also, concentrations 100–5000 μg l−1 were ineffective in most tested species with the exception of P. subcapitata. Growth of P. subcapitata was strongly inhibited at concentrations of microcystin-LR or -RR ≥ 100...