Algae in Recreational Waters: An Overview within a One Health Perspective

Recreational water activities are widely recognized to have a positive impact on our physical and mental well-being. However, recreational water sources and their management are also a risk factor for human health due to different agents, including the overgrowth of cyanobacteria and algae. The presence of cyanobacteria and algae in recreational waters represents a One Health threat because of their potential release and the overuse of biocides. These organisms have the potential to metabolize organic matter and produce thermophilic and thermotolerant toxins. Moreover, different species of algae are involved in biofilm formation processes, thus impacting water quality and safety and also posing risks to the environment and animal and human health. Different species of algae participate in biofilm formation and have an impact on managing water and equipment maintenance. By searching literature databases, e.g., PubMed, we reviewed the state of the art, providing basic definitions, taxonomy, and epidemiological or medical issues related to the recreational uses of water. Methods of treatments and monitoring were summarized, considering both traditional and innovative strategies. Public health and surveillance approaches focus on the detection of toxins, the formation of biofilms, and the understanding of the benthonic and planktonic components as part of the larger microbial biodiversity. The review process allowed us to acknowledge that this is the first comprehensive overview of algae in recreational waters carried out within a wider One Health outlook.