Two species of common edible fish, common carp (Cyprinus carpio) and silver carp (Hypophthalmichthys molitrix), were exposed to a Microcystis spp.-dominated natural cyanobacterial water bloom for two months (concentrations of cyanobacterial toxin microcystin, 182-539 microg/g biomass dry wt). Toxins accumulated up to 1.4 to 29 ng/g fresh weight and 3.3 to 19 ng/g in the muscle of silver carp and common carp, respectively, as determined by enzyme-linked immunosorbent immunoassay. Concentrations an order of magnitude higher were detected in hepatopancreas (up to 226 ng/g in silver carp), with a peak after the initial four weeks. Calculated bioconcentration factors ranged from 0.6 to 1.7 for muscle and from 7.3 to 13.3 for hepatopancreas. Microcystins were completely eliminated within one to two weeks from both muscle and hepatopancreas after the transfer of fish with accumulated toxins to clean water. Mean estimated elimination half-lives ranged from 0.7 d in silver carp muscle to 8.4 d in common carp liver. The present study also showed significant modulations of several biochemical markers in hepatopancreas of fish exposed to cyanobacteria. Levels of glutathione and catalytic activities of glutathione S-transferase and glutathione reductase were induced in both species, indicating oxidative stress and enhanced detoxification processes. Calculation of hazard indexes using conservative U.S. Environmental Protection Agency methodology indicated rather low risks of microcystins accumulated in edible fish, but several uncertainties should be explored.

Centre for Cyanobacteria and Their Toxins Institute of Botany Czech Academy of Sciences Brno Czech Republic

References provided by Crossref.org

Cyanobacteria Microcystis aeruginosa Contributes to the Severity of Fish Diseases: A Study on Spring Viraemia of Carp

Concentrations of microcystins in tissues of several fish species from freshwater reservoirs and ponds

Oxidative stress and detoxification biomarker responses in aquatic freshwater vertebrates exposed to microcystins and cyanobacterial biomass

Toxins produced in cyanobacterial water blooms - toxicity and risks