An assessment of toxic effects of chemical toxicants on biochemical markers in the freshwater snail Helisoma duryi exposed to different water samples from a gold mine

Abstract

Mining operations produce large amounts of waste effluent that contain compounds of varying toxicity that leach into aquatic bodies. We investigated the effects of water samples from a gold mining area on oxidative stress biomarkers in Helisoma duryi. Water was collected from four sites in the mining area: site 1, Mtshabezi water from a river 3 km from the mine and sites 2, 3 and 4 (underground water, waste effluent, process water) at the mine. The water samples were analysed for cyanide and heavy metals. Snails in groups of 30 were exposed to one liter volumes of water from sites 1- 4 and the control for up to 14 days. Cyanide levels in the 0.1 – 0.5 mg/L range were observed in water sampled from sites 1- 4. Cadmium, chromium, copper, lead and zinc were observed in all water samples from the mining area. Superoxide dismutase and catalase activities were enhanced in snails exposed to samples from the mining area. Increased concentrations of malondialdehyde, which indicates oxidative stress were observed in snails exposed to water from sites 1-4, suggesting that mining operations directly or indirectly release pollutants that include oxidative stressors which affect the wellbeing of aquatic organisms.