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What happens to aquatic creatures when ice freezes over?

As winter sets in, we bundle up, turn on the heat, and make sure our pets stay warm. But what about wildlife, especially the creatures living in streams, lakes, ponds, and rivers that may freeze over?

Aquatic organisms have come up with several adjustments to meet these challenges.
 

Fish and other cold-blooded animals adjust their body temperature and modify their behavior according to the season by adjusting their metabolism to the environment they live in. While agile and quick in warmer water, they slow down as their body temperatures drop.

Some fish called cold-water species, like trout, perch, and salmon, actually prefer chilly conditions. Cold water holds more oxygen, which they need. Even so, when water temperatures fall below about 40°F, these fish still move slowly to conserve energy.

Warm-water species, like bass, bluegill, and catfish, take a different approach. They retreat to calmer edges of streams and lakes, burrow into mud or leaf litter, and essentially “hibernate” until spring.

And here’s the wild part: some species can survive being frozen solid and come back to life when things thaw.

Fish aren’t the only organisms in our streams though. Macroinvertebrate, or stream insects, have some unique adaptations to survive the winter.

Like a lot of our warm-water fishes, aquatic macroinvertebrates will burrow into the mud, leaves or other stream substrate til spring. Many insects can also secrete a fluid similar to antifreeze to survive the cold.
 

Other organisms in water? Snails become very inactive in winter. Those present in water that freezes solid, burrow into mud and plant debris to hibernate. Mussels become dormant, too. This is evident from the darker rest rings on their shells, sometimes called “growth rings.” Most frogs hibernate in the mud below the ice, though some survive the winter in their tadpole stage.

Many turtles also burrow into the mud and become inactive during the colder months. Snapping turtles, on the other hand, settle beneath plant debris and logs or even stay in muskrat or beaver burrows. Both snapping and painted turtles become active sometimes and can be seen crawling around under the ice. Cold-blooded toads, water snakes and garter snakes head under decaying logs, in stone piles, burrows or other holes and hibernate.

Nature doesn’t stop in winter. It just slows down.