R Sonia, R Ramanibai
Cyanobacterial blooms are the most common problem in eutrophic or hyper eutrophic water bodies. The blue green algae, Microcystis aeruginosa occurred and dominated during the summer season in Velacherry Lake. Along with M. aeruginosa, M. flos-aquae and M. wesenbergii co inhabit the freshwater habitats. Molly fish were used as animal models to detect the toxicity of microcystins consumed along with the diet intake. Fish were exposed to a known quantity of Microcystis (6 X 104 cells/mL) mixed in an aquarium tank. Survival rate and growth rates were monitored daily. Soon after death, various vital organs of the experimental fish were removed for histopathological analyses. Results revealed that the mortality of the Molly fish may have occurred due to the toxic effect of microcystins. Signs of toxicity exhibited by Molly fish indicated that the bloom samples were predominantly hepatotoxic in nature.