A new medium free of organic carbon to cultivate organisms from extremely acidic mining lakes (pH 2.7)

An algal culture medium was developed which reflects the extreme chemical c onditions of acidic mining lakes (pH 2.7, high concentrations of iron and s ulfate) and remains stable without addition of organic carbon sources. It e nables controlled experiments e.g. on the heterotrophic potential of pigmen ted flagellates in the laboratory. Various plankton organisms isolated from acidic lakes were successfully cultivated in this medium. The growth rates of a Chlamydomonas isolate from acidic mining lakes were assessed by measu ring cell densities under pure autotrophic and heterotrophic conditions (wi th glucose as organic C-source) and showed values of 0.74 and 0.40, respect ively.