Occurrence of an Algal Mass Development in an Acidic (pH 2.5):, Iron and Aluminium‐rich Coal Mining Pond

A bloom of Chlamydomonas botryopara was observed in an extremely acid coal mining pond (pH 2.5) with high concentrations of iron and aluminium (1160...3760 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 μg 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.