Toxin-mediated interaction between cyanobacteria and native fishes in the eutrophic hoedong reservoir, south Korea

Abstract

The microcystin-production responses of Microcystis spp. to the feeding activity of dominant native fishes (Hemiculter eigenmanni and Culter brevicauda) were examined in mesocosm experiments in the eutrophic Hoedong Reservoir and in the laboratory. Microcystin content in feces and toxin accumulation in whole body tissues of fishes were also measured. For fish treatments microcystins were not detected on day 0 but increased from day 1 of the experiment (mean value of 42.3 μg g−1 -dry wt), and were up to six times greater (194.3 μg g−1 -dry wt) than those of controls (33.6 μg g−1 -dry wt) on day 6. Both fish species fed on the alga as reflected in elevated levels of microcystin within their body tissues and feces. Microcystin levels were generally higher in feces than in body tissues. In the field experiment, microcystin was detected in fish body tissues in both of surface (0 m) and subsurface waters (3 m), even though it was not detected in the reservoir water itself in the course of experiment. These results suggest that microcystin production may be induced by exposure to native fishes. © 2003, Copyright Taylor & Francis Group, LLC.