Map: Microcystin monitoring in the Upper Midwest

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About the Map

Map: Microcystin monitoring in the Upper Midwest

By Anne Schechinger, Senior Analyst, Economics


State Microcystin Monitoring
Newsworthy Algal Blooms

Blooms of blue-green algae – actually microscopic organisms called cyanobacteria – and the toxins they can produce threaten people, pets and wildlife across the U.S. Microcystin exposure can cause nausea, vomiting, diarrhea and sore throat and long-term problems like liver failure or cancer. Microcystin and other algae-triggered toxins can be deadly for pets, wildlife and livestock. In the Upper Midwest, algae blooms are commonly triggered when fertilizer and animal manure run off poorly protected farm fields and get into lakes, ponds, rivers and streams.

This map shows lakes, ponds and beaches that have been tested for microcystin in Iowa, Minnesota and Wisconsin.

Testing is limited in all three states, so the map also shows where news stories have reported outbreaks of algae, from 2010 through September of 2020. A news story doesn’t always confirm that the bloom was toxic, because in many cases, tests for toxins weren’t conducted.

Click on the orange dots to see microcystin test results or on the green dots to see algae bloom news reports.

All microcystin tests shown on the map were specific locations where results from tests conducted by state agencies were above the level of detection. Detection levels varied by state and location but tended to be 0.1 ug/L or greater. Since test results that were below the detection level are not reported on the map, locations with those below detection were not included.

Far more regular testing is needed to warn people to stay away from infected lakes.

Read the report here.

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