Microcystin Levels in Eutrophic South Central Minnesota Lakes A study of the blue-green algal toxin – Microcystin - based on select lakes in McLeod and Blue Earth Counties

Blue-green algae, more appropriately referred to as Cyanobacteria, are a common component of the algal community in lakes and rivers in Minnesota and elsewhere in the world. It has been long known that certain forms of blue-greens have the ability to produce toxins and these toxins have been implicated in animal deaths and human-health related problems. These toxins, which include anatoxin, saxitoxin, microcystin and a more recently described toxin cylindrospermopsin vary in their toxicity. And of these, microcystin is the most commonly measured in most studies. While there has long been concern regarding blue-greens and the production of toxins (Carmicheal, 77), recent literature suggests there are numerous efforts in various countries such as, Australia (Brookes and Bruch, 2004), Germany (Chorus, 2001), and the US (Graham et al. 2005) to improve our understanding of this issue, the factors that lead to the toxicity, and our ability to manage the blooms that cause the toxicity. An example of a response from Australia is the Queensland Harmful Algal Response Plan that may be viewed at http://www.nrw.qld.gov.au/water/blue_green/index.html . Blue-green algae have several properties that allow their success in lake communities. Perhaps the most significant is the ability to control their buoyancy to optimize light and nutrient conditions. This property also allows for the build up of scums under some conditions. Algae at the surface water interface can take advantage of abundant light, as well as atmospheric carbon and nitrogen. The build-up of algal scums is not only related to nutrient concentration and buoyancy but is also influenced by chemical and physical factors such as wind, sunlight and available nutrients.