Abstract

A bloom of Chlamydomonas botryopara was observed in an extremely acid coal mining pond (pH 2.5) with high concentrations of iron and aluminium (1 160...3 760 mg L-1 Fe, 133...387 mg L-1 Al). Cell density of algae was counted as 6.45 · 106 mL-1 corresponding to 700 mg L-1 fresh weight and 2660 ?g L-1 chlorophyll-a. The nutrient concentrations were 3.5 mg L-1 soluble reactive phosphorus and 0.15 mg L-1 dissolved inorganic nitrogen. This observation supports the hypothesis that a low nutrient availability rather than extreme conditions (e.g. high acidity and low pH) limit the development of phytoplankton in many acidified lakes.