Microcystin bioaccumulation can cause potential mutagenic effects in farm fish

This study investigated the bioaccumulation of microcystin and its potential mutagenic effects in cage-reared fish. For six months, three reservoirs (Acauã, Cordeiro and Camalau) in arid regions of Brazil were monitored. After five months, 10 fish (Oreochromis niloticus) were collected from each tank, and the amounts of microcystin in their muscles and viscera were analysed. Mutagenic effects were also evaluated. Species of cyanobacteria were present during all months of our study. The highest biovolume of cyanobacteria and microcystin in water occurred in the Acauã Reservoir; this was followed by Cordeiro and Camalau. All fish sampled contained microcystin, ranging from 16.01 to 37.09 ng g−1 in muscle and 228.2–804.0 μg g−1 in liver. We observed significant differences between the micronucleus count in experimental and control fish (p < 0.05), suggesting a potential mutagenetic effect in the experimental fish. In all reservoirs, the fish microcystin level was well above the World Health Organization (WHO) tolerable daily intake, indicating a serious risk to consumers.