Establishing reliable and cost-effective tools to identify the occurrence of toxin-producing cyanobacteria could lead to an early warning system to prevent water consumption and recreational activities, especially for low-income agricultural countries. The current study utilised a two-method approach, an enzyme-linked immunosorbent assay and polymerase chain reaction, to enumerate commonly occurring cyanotoxins: microcystin (MC), cylindrospermopsin (CYN), nodularin (NOD), anatoxin-a (ANA-a), and saxitoxin (SAX), and to evaluate the presence of the genes responsible for producing these toxins. Water samples from 43 drinking, recreational and irrigational water bodies in Sri Lanka were collected between November 2019 and July 2020. Results indicated that 24 of the sampled water bodies contained at least one of the toxin-producing genes screened. Notably, the overall MC concentration detected for Beira Lake in Colombo, a recreational waterbody in the country's largest and most populous city, was 3.31 μg/L. Among the different cyanotoxins analysed, MC was found to be the most dominant (37%) in the collected water samples compared to CYN (10%), SAX (10%), NOD (10%), and ANA-a (10%). This is the first such study where molecular approaches were combined with immunological assays to provide an extensive survey highlighting an alarming level of contamination of cyanotoxins in intensively used water bodies.

  • The study emphasises the worldwide concern regarding the presence of toxic and non-toxic cyanobacteria.

  • Microcystin (MC), cylindrospermopsin, nodularin, anatoxin-a, and saxitoxin are commonly occurring cyanotoxins that are enumerated in this study.

  • MC was found to be the most dominant.

  • The study stands out as the first to combine molecular approaches (polymerase chain reaction) with immunological assays (enzyme-linked immunosorbent assay) to provide an extensive survey of cyanotoxin contamination in water bodies.

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