The toxicity of the cyanobacterium Microcystis aeruginosa to rainbow trout, Salmo gairdneri Richardson

Abstract. Microcystis aeruginosa is a common cyanobacterium of nutrient-rich fresh waters. It has been implicated in a large number of poisoning incidents involving wild and domesticated terrestrial animals. The study showed that a pure strain of M. aeruginosa toxic to mice was non-toxic to rainbow trout immersed in a culture for 10 days. In contrast, when presented by intraperitoneal injections Microcystis caused an acute toxic response with 100% mortality of fish within 36 h. The histopathology of the response is described and contrasted with that to another cyanobacterium, Anabaena cylindrica , which was shown to be non-toxic by immersion or injection.