Life Under the Ice | Prairie Public Broadcasting

Life Under the Ice

Dec 21, 2019

Most of the lakes and ponds in the state now have a lid on them. I suspect that the casual observer may think that what goes on in the water below probably hasn’t changed much other than the water is colder. But there is a lot more to it.

The water temperature of course changes. But under that ice the water will stay between about 4 degrees and the freezing point until the spring melt. Think about that for a minute! Those organisms never have to deal with below zero temperatures! It makes one kind of envious!

But once the body of water has frozen over, the exchange of gases with the atmosphere, for example oxygen, has effectively stopped. As a result, oxygen levels in the water will gradually drop throughout the winter.

Algae can continue to carry out photosynthesis which gives off oxygen as a byproduct. Think of them as little aerators. But that can change quickly if the snow accumulates and blocks much of the sunlight. Then all bets are off, and oxygen levels may drop to the point of causing a winter kill.

All those cold-blooded animals that stay active throughout the winter are going to move slower with the colder temperatures. And that includes fish. Their metabolism slows down and their activity is more limited. A way to relate to that is to compare the fight of a northern pike caught in the summer to that caught through the ice. Summer wins every time!

Some cold-blooded species are known to acclimatize to the colder temps and compensate for the colder conditions by raising their metabolic rate. It is sort of like what happens to plants when they become cold hardy as winter approaches Much of this is thought to be the result of the types and amounts of enzymes produced.

There are many other changes going on as well. So, as you pass by the lakes and ponds this winter, give some consideration to how conditions have changed under the ice and how life has adapted to those changes.

-Chuck Lura