An International Survey of Cyanobacteria Risk Management in Recreational Waters: Methods, Principal Taxa and Toxins, Challenges and Perspectives.

World Health Organization (WHO) guidance on the management of cyanobacteria in recreational waters provides a comprehensive framework for reducing human health risks. To provide a global overview of how cyanobacterial risks in recreational waters are managed and to better understand capacity gaps and best practice, we surveyed expert opinion across the world. A total of 161 survey responses were collected from 49 countries. Results indicate widespread variation in the extent of recreational water monitoring. Routine monitoring often varies by region in larger, more populous countries, while seasonal monitoring, typically conducted at variable intervals, was the most used approach. Approximately half of the countries reported either a lack of routine monitoring or a combination of different monitoring patterns. Notably, whereas nearly all countries reported methods for planktonic sampling, only one-third of countries reported methods for benthic sampling. Globally, we conclude that the assessment and management of benthic cyanobacteria risks lag behind that of planktonic cyanobacteria risks. Cell counts and pigments were the most common assessment techniques for planktonic cyanobacteria. Microcystis and Oscillatoria were the most frequently reported problematic genus of planktonic and benthic cyanobacteria, respectively, and microcystins were the most frequently reported cyanotoxins of concern. A wide variety of management responses and risk communication methods were reported with the primary action trigger being the presence of cyanobacterial scums. Experts across the world were mostly unsatisfied with recreational water risk management regimes, with over 80% of respondents desiring change in how cyanobacterial risks are managed. We conclude that a renewed international effort is needed to enhance collaboration and knowledge exchange and sustain investment to ensure safer recreational waters at a global scale.