Microcystins (MCs) are the most prevalent freshwater cyanotoxins worldwide and pose significant threats to both public health and aquatic ecosystems. Effective harmful algal bloom (HAB) surveillance depends on accurate, continuous monitoring of MCs, but current grab sampling methods are labor-intensive, require large water volumes and frequent field visits (typically weekly), and fail to capture temporal variability. While automated samplers offer higher temporal resolution, their high cost, power dependency, and maintenance needs hinder their use for long-term or wide-scale deployment. These limitations highlight the need for more practical, low-cost approaches. Passive sampling, particularly the Polar Organic Chemical Integrative Sampler (POCIS) developed for hydrophilic pollutants, offers a promising alternative. POCIS enables time-weighted average (TWA) concentration measurements, lower detection limits for trace-level contaminants, and autonomous operation without power or frequent maintenance. Although POCIS has been validated for pollutants such as pharmaceuticals and pesticides, its application for MC monitoring remains underexplored, with no reports of long-term deployment in natural systems. This project aims to develop, calibrate, and demonstrate a passive sampling method for TWA monitoring of MCs in HAB-impacted lakes. Specific objectives include: 1) Laboratory calibration of POCIS using static renewal for multiple MC congeners, 2) In situ calibration in Hyde Lake and comparison with lab-derived uptake rates, and 3) Field deployment of POCIS samplers for a pilot MC monitoring across pre-, peak-, and post-bloom stages.
