Under the Ice
Outside of the occasional ice fishing hole, ice cover keeps lakes fairly secretive this time of year. What’s
going on under there?
Fish have more room to swim in the winter because oxygen is spread more evenly throughout the lake.
In warmer months, distinct layers form in the lake because the sun heats the surface, and fish are
restricted to the upper water where there is the most oxygen.
Yet despite more freedom to move around, life slows down to conserve energy. Fish swim slower, frogs
go dormant and turtles breathe as rarely as once per day.
The ice also keeps new oxygen from entering the lake, and in especially long winters or shallow lakes the
oxygen can run out and cause a fish kill. Gleason Lake in Wayzata suffered a partial fish kill last winter.
Almost all aquatic plants are perennials, and will “die back” during the winter and return in the spring.
One exception is the invasive plant curly leaf pondweed, which stays green year-round. Zebra mussels
also survive the winter underwater, though the ice will remove them from rocks and shallow areas.