Whitefish (Coregonus lavaretus) Response to Varying Potassium and Sodium Concentrations: A Model of Mining Water Toxic Response

Boreal waters are typically low in minerals and oligotrophic, and therefore particularly sensitive to changes in mineral composition. We investigated the effects of potassium and the potassium: sodium (K+: Na+) ratio in freshwater on growth performance and oxidative stress in a typical northern species of whitefish, Coregonus lavaretus. Fish were subjected to 0.8 mM Na and 4.4 mM K, which corresponds to the K+:Na+ ratio in a lake contaminated by mining wastes from the Kostomuksha iron mine and ore dressing mill in northwestern Russia. The control group was subjected to water with similar mineralization levels and equal amounts of Na and K (approximately 0.3 mM of each). Potassium excess caused a decrease in fish growth rate and oxidative stress, as indicated by the level of lipid peroxidation product malondialdehyde (MDA). Glutathione-S-transferase (GST) activity and the level of reduced glutathione (GSH) were not affected by cation composition.