Aluminium and calcium — Key factors determining the survival of vendace embryos and larvae in post-mining lakes?

Abstract

After decommissioning of many open-cast lignite mines, numerous acidic post-mining lakes have formed in the Lusatian district (eastern Germany). With regard to (1) plans for neutralisation and subsequent use of these lakes for fisheries and (2) the risk of reacidification of previously neutralised lakes, the effects of acidic post-mining lake water on fish are of major interest. In order to investigate the contribution of Al to overall toxicity and to assess whether the high Ca content of the lakes has a protective effect, early life stages of vendace, Coregonus albula, were exposed for 60 days to nine combinations of pH, Al and Ca in reconstituted post-mining lake water. Low pH (pH 4.75 and 5.00) associated with 1.0–1.1 mg l −1 Mn and 0.1 mg l −1 Fe did not reduce hatching success and survival during the embryonic and early larval development when the Al concentration was low (0.1–0.2 mg l −1). However, when the Al content was increased to 2.4 and 2.1 mg l −1 at pH 4.75 and 5.00, respectively, mortality prior to hatch was high, no (pH 4.75) or very few embryos (pH 5.00) hatched, and no fish survived to the end of the experiment. Increasing the Ca concentration from 111–117 mg l −1 to 233–256 mg l −1 had no influence on hatching and survival percentages. Thus, the deleterious effect of the high Al concentrations (2.4 and 2.1 mg l −1) was greater than the protective effect of the high Ca content.