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Project 17

Project title: Effects of nutrients and exotic herbivores on the genetic structure of harmful cyanobacterial populations
Investigators: Orlando Sarnelle, Julianne Dyble
       
Abstract:  Cyanobacteria are the most important taxa causing harmful phytoplankton blooms (HABs) in freshwaters.  Toxins produced by cyanobacteria constitute a priority research area of the CWS with respect to human health because of the risks presented by these toxins in drinking and recreational waters.  Although it is well-established that nutrient enrichment strongly stimulates cyanobacterial abundance, several factors can greatly modify predictive relationships between nutrient levels and toxin levels in freshwaters.  We will investigate two of these factors with a multidisciplinary study of the ecology and population genetics of Microcystis aeruginosa, a major toxin-producing cyanobacterium.  We seek venture funds to couple genetic studies of M. aeruginosa with ongoing field experiments on the effects of nutrients and an exotic herbivore (Dreissena polymorpha) on M. aeruginosa.  The field experiments are being conducted in Gull Lake and Lake Erie over the next two summers and are funded by an ECOHAB grant from EPA.  Venture funds will be used for genetic analyses of M. aeruginosa colonies isolated from each replicate (enclosures, tanks) of the field experiments.  The genetic analyses will test whether nutrient enrichment and selective grazing by Dreissena differentially favor toxin-capable genotypes of M. aeruginosa over toxin-incapable genotypes. Genetic analyses will consist of: 1) general strain differentiation via characterization of the ITS region of the 16S and 23S rRNA genes, 2) presence/absence of the mcyB gene that encodes for the toxin microcystin, and 3) DNA sequencing of mcyB to map genetic variation onto structural variants of microcystin.  Structural variants have different toxicities, so this mapping is aimed specifically at improving the accuracy of risk assessments.  Venture funds, and the data they generate, will enable us to submit stronger proposals to the NSF/FIBR program (Frontiers in Integrative Biological Research) and the ECOHAB program (multi-agency: EPA, NOAA, NSF, NASA, ONR).  Both programs have annual or biannual rfp's with deadlines in January/February).