Toxic cyanobacteria in some finnish lakes

Abstract

The frequency and toxicity of cyanobacterial blooms in three different lake systems were investigated during the years 1985–1987. Toxicity was tested by i.p. mouse bioassay. Cyanobacterial blooms in Lake Tuusulanjärvi were dominated by Microcystis aeruginosa and Aphanizomenon flos‐aquae. Whenever toxicity occurred the samples were always hepatotoxic. Lake Sääskjärvi blooms were generally composed of Anabaena circinalis and A. flos‐aquae. Toxicity in Lake Tuusulanjärvi fluctuated between sampling intervals whereas Lake Sääskjärvi showed periodic toxicity, i.e., neurotoxicity caused by anatoxin‐a occurred at times of A. circinalis dominance. This proved to be fatal for surrounding livestock. In Lake Haukkajärvi and adjoining lakes the blooms were mainly composed of Anabaena flos‐aquae and Anabaena lemmermannii; here also the blooms were neurotoxic, although this time caused by an unknown toxin(s).