Aquatic Life makes adjustments during winter

As humans grudgingly take precautions during winter, we complain and feel better. Our counterparts in nature also have to make adjustments, but their complaints are heard less often.

During the winter, aquatic organisms face the challenge of adjusting to temperatures low enough to freeze their homes. To deal with this, organisms have come up with a number of different strategies to survive. These range from remaining active to slowing down their activity to sleeping through the winter. There are a few winters I would have liked to sleep through.

As temperatures fall outside, life present in and around streams and ponds takes a dramatic turn. Water in the pond freezes over, enclosing and protecting animals that sleep through the winter nestled in mud and those that remain active. In the slower moving pools of streams, ice forms over the top of the water. However, ice may never form over the more rapid riffles.

When this happens, the life within the creek must prepare for a long winter spent at a body temperature of only 4 degrees Celsius. Although many organisms die, they leave behind eggs and seeds as their method of survival. Duckweed, for example, deposits tiny green scales during the winter months. As springs rolls around, the scales surface and grow.

Most aquatic plants die in autumn to prepare for winter. However, they only die back to their roots, which means they can grow back when the weather gets warmer. Plants that are partially submerged either wholly or partly disintegrate during the winter. Algae, on the other hand, remain photosynthetic all winter long or survive as spores in a dormant state in most cases.

Fish and other cold-blooded animals adjust their body temperature and can modify their metabolism to the environment they live in. They are fast and nimble in the summer because the water temperature is much warmer, but in the winter they slow down as their body temperatures drop.

Some fish -- such as the trout, salmon, pike and yellow perch -- are especially designed to deal with this.

Even at low temperatures, their bodies allow them to swim easily. They often take refuge in the deepest part of the stream or pond where the water is warmest. Other fish, such as bass, sunfish and catfish, must hibernate (pass the winter in a resting state) due to their inability to cope with the cold water. They move to the edges of the stream or pond and bury themselves in mud or leaves. There they wait until they can successfully swim again.

Bullheads, and other members of the catfish family can often become completely frozen during the winter, thaw in spring and live without harm. This is an amazing adaptation to the winter season.

Fish are not the only creatures living in the streams during the winter. Insects also have adaptations to survive the winter. Many invertebrates burrow in the mud or leaves for the winter. Spending their time as eggs, larvae, pupae or adults, insects often secrete a fluid that is similar to antifreeze in order to withstand the cold. Huddled masses of insects called water boatmen and backswimmers can sometimes be seen in small air pockets under the ice.

When the occasional early spring thaw melts the surface ice, water striders and diving beetles swim in the near freezing water. Dragonflies and damselflies perform a similar task, but in the larval stage.

Aquatic sowbugs also are active. Many waterfleas display rounded heads in winter, when the water is cold, and pointed heads in summer, during periods of warmth. (The pointed head is thought to be an adaptation to increased predation in the summer.)

Horsehair worms have a unique solution to the problem of winter temperatures. They choose to either hibernate among shore plants or to remain in the host body and parasitize.

Snails become very inactive in winter. Those present in water that freezes solid, burrow into mud and plant debris to hibernate. Some water mites may temporarily do this as well.

Mussels become dormant (inactive), too. This is evident from the darker rest rings on their shells, sometimes called “growth rings.” Mussels do not grow during the winter, yet they are sometimes seen active through clear ice.

Crayfish remain active, but not as active as they are in the summer. They tend to burrow into wet meadows, river banks and other wetlands. Leeches become dormant and bury themselves in mud or plant debris. Adult newts and mudpuppies remain active, while salamanders hibernate under logs and stones. 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.

Maybe we can all crawl slowly above the ice until the economy turns around.

Michael P. Gutzmer, PhD is an environmental consultant with New Century Environmental LLC and helps solve environmental challenges throughout the United States. He can be reached at mgutzmer@allaboutlakes.com