Global warming translates to shorter lake ice cover

Many of us northern Minnesotans enjoy winter on the lakes as much as summer.  There are so many possible activities such as ice-fishing, snowmobiling, cross country skiing and snowshoeing.  So how will we react when the duration of ice cover on our lakes declines due to global warming?  In addition, how will a shorter ice cover affect our lakes and their fish communities?

Researchers at the St. Anthony Falls Laboratory of the University of Minnesota have been studying these effects for the past decade.  They studied 143 North American Lakes, half of them from Minnesota and found depending on how much the yearly average air temperature increases, yearly ice cover can reduce by as much as 11-25 days.  Reducing ice cover by 11 days doesn't sound like much, but our winter ice season will actually be shortened by more than 11 days because of the decline in duration of "safe ice" conditions.

First of all, a shorter "safe ice" season will shorten our winter lake activity season.  We'll have to wait longer in late fall to get out on the ice and we'll have to be off the ice earlier in the spring.  This will be tough!

A longer ice-free season for the lake translates to a longer growing season for algae.  We might be happier about a longer growing season for our gardens, but we probably won't be as excited about more algae.  The lakes will also get warmer overall because of the extra days of exposure to the sun, which will increase evaporation from lakes and cause lake levels to decline.

For fishing, global warming effects could be good or bad, depending on what fish you like to catch and what lakes you fish on.  Individual fish actively select and rapidly change living areas based on suitable temperatures, oxygen concentrations, and food availability. As water temperatures in the region increase, cold-water species such as lake trout, brook trout, and whitefish may decline dramatically, as cool-water species such as muskie and walleye, along with warm-water species, such as bluegill and smallmouth bass, expand their ranges northward. As a result of these changes, anglers may lose their preferred catch or have to travel further north to fish certain species.

A shorter ice cover will decrease the likelihood of a winter fish kill, shortening the time when the lake is cut off from outside sources of oxygen.  However, in turn a longer summer season will increase the likelihood of a summer fish kill in shallow lakes, due to less oxygen at the bottom of the lake for a longer period of time.

Native species of plants, fish, frogs, insects and other aquatic organisms could be lost due to the inability to adapt to warmer temperatures.  Invasive species, which can adapt to a wider range of habitat conditions could come in and take the place of native species.

Researchers continue to find new changes and effects to our ecosystems due to climate change.  Only time will tell how fast and how severe these effects will occur.  To read more about this topic, you can visit: http://www.ucsusa.org/greatlakes/glregionmin.html.

Until next week, enjoy the lakes!

Moriya Rufer is the Lakes Monitoring Program Coordinator for RMB Environmental Laboratories in Detroit Lakes, 218-846-1465, lakes.rmbel@eot.com.