Evaluation of Indicators for Cyanobacterial Risk in 108 Temperate Lakes Using 23 Years of Environmental Monitoring Data
Abstract Background: Cyanobacterial blooms are of increasing concern for drinking water supply. Cyanobacterial risk in 108 temperate freshwater lakes were examined for drinking water supply. Results: In Sweden, a survey among drinking water producers showed that the sense of urgency was little. At 60 % of the Swedish drinking water treatment plants, operators lacked monitoring strategies. The study shows that blooms can produce a variety of toxins such as anatoxins, cylindrospermopsins, microcystins and saxitoxins. We confirmed the anthropogenic activities’ impact on cyanobacterial risk and evaluated that total phosphorus (TP) concentration can be used to indicate cyanobacterial risk by applying non-linear quantile regression for 108 Swedish monitoring lakes.Conclusion: We suggest that TP concentration should be investigated thoroughly to provide important knowledge which can be used to set nutrient targets to sustain safe drinking water supply and recreational services.TP should be targeted lower than 15 μg L-1, allowing 10 % exceedance of WHO Drinking Water Alert Level 1.