Toxicity of a soluble peptide from <i>Microcystis</i> sp. to zooplankton and fish

Abstract

SUMMARY. A soluble cell fraction lethal to Daphnia magna was isolated by the disruption of net phytoplankton from eutrophic Aculeo Lake. The phytoplankton of this lake is dominated by Microcystis sp. The soluble fraction was also lethal to common native zooplankton, including the rotifers Keratella sp., Trichocerca similis , the copepod Boeckella sp., and the cladoceran Chydorus sphaericus . In addition, a partially purified soluble component of the lethal fraction caused the death of the fish Gambusia affinis . The specific toxicity of the soluble fraction from phytoptankton varied four‐ to six‐fold seasonally with peaks during periods of warm temperature. Our results suggest that releases of a toxic peptide from Microcystis sp. may be the cause of massive fish kills at the study site, Aculeo Lake.