Abstract
Cyanobacterial populations in surface waters, including drinking water supplies and recreational waters, represent an ever present challenge for resource managers. As communities continuously respond to external and internal processes, dynamic profiles of composition, dominance, growth and toxigenicity emerge. In this study measures of size structure and biomass, quantified using light microscopy and fluorometry, were used to estimate microcystin concentrations through linear regression analysis. Toxigenic profiles using cyanobacterial biomass were developed for lakes dominated by Microcystis spp. and Dolichospermum spp., influenced by both genus-specific pigment concentrations as well as microcystin concentrations. Community composition (Log %MIC) and biomass were used to describe microcystin concentrations in mixed assemblages, where composition was the first input variable. The accessory photopigment phycocyanin was used to describe the linear relationship between the daily growth and net microcystin production rates in the bloom-forming Microcystis spp. samples, suggesting that this size-fractionated sample may provide indications of potential toxigenicity in the whole lake water sample. Future investigations using fluorometric evaluation of cyanobacterial populations could provide additional applications and metrics for use by resource managers to quantify risk association with elevated cyanotoxin concentrations.
Highlights
Many programs have been developed to evaluate and manage exposure to cyanotoxins in recreational waters and drinking water supplies
Toxigenic profiles using cyanobacterial biomass were developed for lakes dominated by Microcystis spp. and Dolichospermum spp., influenced by both genus-specific pigment concentrations as well as microcystin concentrations
During our study only one lake (Lower Mill Pond) consistently had Chl-a concentrations in the
Summary
Many programs have been developed to evaluate and manage exposure to cyanotoxins in recreational waters and drinking water supplies. Traditional methods rely upon cell counts and toxin analysis to initiate responses to protect human health, it has been noted that these methods require expensive and time consuming laboratory analyses, potentially increasing the risk of exposure. As such there is a great need for assessment techniques that provide critical information that is of high quality, timely, low cost, and supports initiation of preventive (rather than responsive) measures. These include site specific models using environmental variables that influence the biomass of cyanobacteria [5] [6], measurements of increased cyanobacteria and elevated microcystin concentrations [5] [6] [7] [8] [9], and the influence of community structure on microcystin concentrations using light microscopy [8] [9], cell counts [5] and qPCR [5] [7]
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