Enhanced Monitoring Strategies for Toxic Cyanobacteria in Drinking Water Supplies
Clarke Brown, Dave Redden (Centre for Water Resources Studies)

Globally, harmful cyanobacteria blooms cyanoHABs are becoming more frequent and are of greater magnitude and duration’— a trend that is expected to continue as eutrophication and a warming climate create conditions that are increasingly favorable for cyanobacteria. Many, but not all, cyanobacteria produce secondary metabolites cyanotoxins that pose risks to ecosystem functions and public health. The ability to detect low concentrations of cyanotoxins ‘— or indicators of the potential for cyanotoxin production’— ensures that appropriate mitigative measures can be implemented before concentrations reach guideline levels.

In this work we will present monitoring strategies that utilities can consider to enhance monitoring of surface drinking water supplies for cyanobacteria and their associated toxins. Specifically, our goal was to identify monitoring tools that can potentially provide an early warning of cyanotoxin presence, including quantitative polymerase chain reaction qPCR and passive sampling. We used qPCR to detect genes responsible for the production of cyanotoxins, while passive sampling was used to detect cyanotoxins at concentrations that may not be detectable through traditional grab sampling methods. We monitored six recreational lakes with histories of suspected cyanoHABs and four drinking water supply lakes, two of which experience recurring cyanoHABs. At each of the study lakes, we collected weekly samples between spring and winter of 2022 and 2023. Generally, at several locations we observed a rise in the presence of cyanotoxin producing genes, followed shortly thereafter by the presence of toxins. These tools can be used to develop a proactive cyanotoxin monitoring program to effectively identify risks associated with cyanotoxins in advance of it becoming a public health threat.