Occurrence of cyanobacterial toxins?microcystins and anatoxin-a?in Berlin water bodies with implications to human health and regulations

Main Berlin waterways are lowland rivers Spree, Dahme, and Havel, which are connected to some shallow lakes. High nutrient concentrations support heavy blooms of cyanobacteria which produce toxic substances (“cyanotoxins”). Concentrations of microcystins (MC), anatoxin-a, chlorophyll-a, and cyanobacterial biomass were analyzed in surface water. Two methods [enzyme linked immunosorbert assay (ELISA) and high-pressure liquid chromatography (HPLC)] were used for MC analysis. Different preparation techniques were carried out determining dissolved and cell-bound microcystins. Furthermore, the health implication for people using lakes for swimming and recreation was assessed as a basis of a proposal to health and water authorities for further regulations. Concentrations of total (cell-bound and dissolved) microcystin (with ELISA) varied between 0.14 and 119 μg/L; 95 of 128 samples showed values above 1 μg/L (nearly 74%), 49 above 10 μg/L (nearly 38%), and 2 above 100 μg/L (nearly 2%). With wide variability, concentrations of microcystins measured with HPLC were 65% (median) of values obtained using the immunologic method. Compared to total microcystin concentrations (dissolved and cell-bound toxin) proportion of dissolved toxin varied from 0.3 to 12% (n=46; mean: 4%). Using animal toxicity data for risk assessment we assume that for children a single intake of 25 μg MC-LR has no adverse effects. Under conservative uptake assumption for contaminated water a concentration of 100 μg MC/L in surface water is safe. On this basis, regulations (as provisional orientation) are proposed to health and water authorities. Levels of anatoxin-a measured in 14 surface samples of two Berlin lakes (Unterhavel and Müggelsee) were under detection limit of 0.01 μg/L.