Passive Samplers and qPCR Analysis: A Potential Detection Method for Cyanobacteria in Drinking Water Sources

Abstract

The synergistic effects of climate change and lake recovery are expected to increase the intensity and frequency of cyanobacteria harmful algal blooms (HABs) in surface waters. Many drinking water sources experience HABs but surveillance strategies lack consistency between provinces and territories. The purpose of this project was to investigate passive sampling and qPCR analysis as a monitoring strategy for cyanobacteria in drinking water sources. A proof-of-concept field-scale monitoring program was conducted at Lake Fletcher, NS that compared traditional grab sampling to a new passive sampling technique using cellulose nitrate filter membranes. Weekly passive and grab samples were paired for analysis and results showed that passive samplers were more effective at detecting cyrA (cylindrospermopsin gene) and sxtA (saxitoxin gene) at all three sampling locations. mcyE/ndaF (microcystin/nodularin genes) was detected more frequently in grab samples at only two of the three sampling locations. Moreover, passive samplers were able to detect cyrA (all locations) and mcyE/ndaF (one location) before grab samples, highlighting their potential for early monitoring strategies. The adsorption performance of four passive sampler materials (cellulose nitrate, acrylic copolymer, gauze and nylon) for cyanobacteria detection was assessed through bench-scale adsorption studies to determine if other materials were more suitable for passive sampling. Cellulose nitrate was the best performing adsorbent and is suspected to reach its maximum adsorption capacity between 1 x 105 – 1 x 108 GU/cm2. These results have demonstrated that with further optimization, passive sampling paired with qPCR analysis could serve as a detection method for potential toxin-producing cyanobacteria in drinking water sources.