Alternative Methods for Analysis of Cyanobacterial Populations in Drinking Water Supplies: Fluorometric and Toxicological Applications Using Phycocyanin

Abstract

The management of cyanobacteria and potential exposure to associated bio-toxins requires the allocation of scarce resources across a range of freshwater resources within various jurisdictions. Cost effective and reliable methods for sample processing and analysis form the foundation of the protocol yielding reliable data from which to derive important decisions. In this study the utilization of new methods to collect, process and analyze samples enhanced our ability to evaluate cyanobacterial populations. Extraction of phycocyanin using the single freeze thaw method provided more accurate and precise measurements (CV 4.7% and 6.4%), offering a simple and cost-effective means to overcome the influence of morphological variability. In-vacuo concentration of samples prior to ELISA analysis provided a detection limit of 0.001 µg•L −1 MC. Fractionation of samples (<0.2 µm, <2.0 µm, <50 µm, WLW and BFC) influenced our interpretations and improved our ability to establish a causa-tive relationship between phycocyanin and microcystin levels in two aquatic systems with distinctly different cyanobacterial populations. In a Microcystis spp. dominant system Log MC (ng•L −1) = −0.279 + (1.368 * Log PC (µg•L −1) while in an Aphanizomemon spp. dominant system Log MC (ng•L −1) = 0.385 + (0.449 * Log PC (µg•L −1). These methods and sampling protocol could be used in other aquatic systems across a broader regional landscape to estimate the levels of microcystins.