Effects of bioheapleaching technology utilizing metal mine emissions on fish in boreal freshwaters

Abstract

Emissions from metal mining activities are known to deteriorate the quality of aquatic habitats and impair the condition and reproductive potential of fish. Metal extraction by biomining methods has been considered to cause fewer emissions, but for example in Finland, the impacts of a bioheapleaching technology utilizing metal mine on the local freshwaters have been substantial. In this thesis, the impacts of the bioheapleaching mine emissions on three native fish species, brown trout (Salmo trutta) European perch (Perca fluviatilis) and whitefish (Coregonus lavaretus pallasi), were investigated. Manganese and sulphate concentrations have been elevated in the mining impacted waters, and in our laboratory experiment with whitefish early life stages, a continuous exposure to manganese sulphate increased the early life stage mortality and impaired the larval growth and yolk consumption. In addition, the tolerance of the whitefish early life stages to manganese sulphate varied among the female parents, and the tolerance also seemed to be linked to larval metallothionein messenger RNA induction. In the long-term in situ egg incubation experiment, however, no mining impact related effect on brown trout and whitefish embryonic mortality or growth was observed. Although low water pH increased the embryonic mortality of both species, the low water pH was characteristic to the waterbodies at the study region in general. With wild male perch, the liver and testes size were lower in the mining impacted study lakes, indicating lower energy resources compared to the males from the reference lakes. The perch from the mining impacted lakes also had lower sperm counts, which seemed to have been compensated by elongated sperm motility. These results suggested that the condition and reproductive potential of fish may have been compromised in the bioheapleaching mine impacted lakes.