Warmer water temperature changes Minnesota lakes

Minnesota's waters draw millions of anglers and water recreation users each year. Minnesota has over 150 fish species, more than 10,000 lakes and thousands of miles of rivers. While it is difficult to predict how much the climate of Minnesota will change in the future, there is general agreement amongst scientists that a warming trend is occurring and will continue.

Warmer temperatures lead to more evaporation, droughts, and more frequent heavy rainfalls. These in turn result in lower lake levels, warmer waters, and reduced water quality.

Native aquatic plant and animal species will differ widely in how they respond to changing water temperatures and hydrology. Some will adapt, some will move further north, and some will decline.

The rising water temperatures could also change the kinds of fish we find in our lakes: there will likely be less cold-water species, like trout, and more warm-water species, such as bass.

Many native species may have trouble adapting to changing habitats. But, a changing climate is likely to benefit invasive species with generalized habitat and feeding requirements. The spread of non-native nuisance species is likely to further increase the impacts of climate change on Minnesota's aquatic ecosystems.

A warming climate increases the duration of summer stratification in deep lakes. Lake stratification occurs when a warm surface layer of water develops over cooler, deeper water. Longer stratification can lead to "dead zones"-areas of water depleted of oxygen and unable to support life. Dead zones, in turn, can result in toxic algal blooms; foul-smelling, musty-tasting drinking water; damage to fisheries; and fish kills-known as "summerkill."

Declines in how long ice covers lakes in winter are expected to continue. The loss of winter ice may have varied effects. It could reduce winterkill from low oxygen levels in shallow lakes, but could also harm fish reproduction.

Another consequence of warmer temperatures is increased decomposition and release of nutrients and contaminants from bottom sediments. Phosphorus and mercury releases would increase, which would lead to more algal blooms and higher mercury levels in fish.

For more information on global climate change and lakes in general, email us at lakewaves@dnr.state.mn.us .