The Mississippi River headwaters and two Lake Superior beaches, along with hundreds of other lakes and river segments, have been added to the state's list of waterways that are "impaired" due to pollutants or other problems that threaten fish, plant life or public health.
The additions, outlined in a report released Wednesday by the Minnesota Pollution Control Agency (MPCA), are part of federal environmental reporting requirements as well as a 10-year effort by the state to assess all 80 of its watersheds.
More than halfway complete, the inventory has found impairments in roughly 40 percent of the bodies of water that it has checked statewide.
"More than half of the waters are not impacted, and that's good," said Glenn Skuta, director of the MPCA's watershed division. "But that's still a pretty high percentage of waters that are not doing as well as they should be. It just points out the need for us to develop a better water ethic in Minnesota."
Testing over the past two years found 582 new sources of pollution in 318 lakes, rivers and streams. That included 304 stream segments and nine lakes that can't fully support fish and aquatic life, plus 87 bodies of water with high levels of phosphorus, which can breed algae and disrupt the oxygen levels needed for healthy plants and fish.
Tests found elevated mercury levels in fish in the section of the Mississippi extending north and east from the headwaters to Cass Lake in Beltrami County. Primarily a product of coal-burning power plants worldwide, excessive mercury can contaminate fish, which can then present health risks if they are caught and eaten, Skuta said.
The state typically issues fish consumption advisories for such contaminated waterways. Excessive mercury consumption is particularly bad for pregnant women due to the known link to birth defects.
With the new listings, the state now knows of 4,600 lakes, streams or segments of rivers that are considered impaired.