Oxygen levels dropping faster in freshwater lakes than in the oceans, according to new research from the University of Minnesota and Rensselaer Polytechnic Institute in New York.
Published on Wednesday, June 2, in the academic journal Nature, the findings say that the trend is driven largely by climate change and land use, and that it threatens biodiversity and drinking water quality.
Researchers analyzed nearly 400 lakes around the world, including 84 in Minnesota.
The research team discovered that oxygen levels in lakes between the tropics and polar regions have declined 5.5% in surface waters, and 18.6% in deep waters since 1980; that in a large number of lakes polluted by phosphorus or other nutrients, falling oxygen levels indicate rising water temperatures and harmful algal blooms; and that oxygen-poor lakes release more methane, a powerful greenhouse gas, into the atmosphere.
This project is the first to document dramatic loss of oxygen in the deep waters of lakes around the world, said co-author Gretchen Hansen, assistant professor of fisheries ecology at the U of M’s College of Food, Agricultural and Natural Resource Sciences.
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At particular risk are critters that rely on cold, oxygenated water, including lake trout.
Hansen credited Minnesota for its efforts to restore and protect watersheds. Protecting forested watersheds and using best management practices on farmland can help reduce the amount of oxygen-stealing nutrients that end up in lakes.
The research was funded by the National Science Foundation.
