Harmful algal blooms of the cyanobacterium Microcystis cause deleterious effects in aquatic organisms: Implications for freshwater biodiversity conservation

Anthropogenically driven harmful algal blooms (HABs) continue to increase in frequency and intensity in the Great Lakes. Risks to human health from HABs drives much of the concern that motivates efforts to manage their causes. However, emerging evidence indicates that HAB-associated toxins, such as microcystins, produced by the cyanobacterium Microcystis, can be toxic to aquatic organisms, especially at sublethal concentrations. Whether this poses a threat to aquatic food webs and freshwater biodiversity is unclear, but understanding the risks associated with sublethal exposures requires toxicological assessment at concentrations commensurate with those typically detected in the field. Herein, we present the results of some of our recent studies assessing the toxicity of microcystins produced by a toxigenic strain of Microcystis aeruginosa on key functional traits (survival, growth, reproduction) of zooplankton (Daphnia magna) and fish (Rainbow Trout, and Lake Trout). We further investigated molecular-level impacts using nontargeted proteomics to link sublethal toxicity with adverse outcomes occurring within these organisms. Our results demonstrate that microcystins at naturally occurring concentrations induced sublethal toxicity in all three organisms, including growth and reproductive impairment, oxidative stress, and carcinogenesis. Taken together, our results demonstrate that Microcystis blooms have the potential to cause deleterious health effects in wildlife.