Minnesota Lakes Gasping for Air

MINNEAPOLIS (MNC) –  Just as humans need clean air to breathe, lakes need healthy oxygen levels to provide habitat for fish species. But a new study said in Minnesota and around the world, freshwater lakes are in trouble with temperatures on the rise.

The research, published in the journal Nature, looked at nearly 400 lakes across the globe, including more than 80 in Minnesota.

It concluded, driven by climate change and warming temperatures, lake oxygen levels are declining as much as nine times faster than oceans.

Kristen Blann, freshwater ecologist for The Nature Conservancy, said if mitigation efforts aren’t prioritized, Minnesota lakes and fish could look a lot different in the coming years.

“What we end up with is the opportunistic generalists that can survive extremes and poor conditions, and we’ll lose many of the species that we most appreciate for the unique ecosystems that they represent,” Blann explained.

For example, lake trout could be affected because they need cold water with ample oxygen levels to survive. And with other research that puts Minnesota among the fastest-warming states, Blann pointed out it creates a greater sense of urgency, as habitats could see dramatic change much sooner.

Gretchen Hansen, assistant professor in the Department of Fisheries, Wildlife and Conservation Biology at the University of Minnesota and a co-author of the study, said there’s another side effect to worry about.

“As lakes warm, the bacteria that can live in those oxygen-depleted waters are bacteria that produce methane,” Hansen noted. “And so, the lakes will produce even more greenhouse gases, contributing even more to global climate change.”

Blann added The Nature Conservancy is working with the state and other partners on programs to protect the watersheds feeding into freshwater lakes, to help make them more resilient.

“The more we can minimize the amount of exposed soil, and concrete and pavement, the healthier those watersheds will be,” Blann asserted.

A key example she cited is conservation work in agriculture to reduce nutrient runoff from farm fields. Meanwhile, Minnesota researchers plan to take a more detailed look at declining oxygen levels in lakes around the state.