Nature Notebook – Who’s moving under the ice?

As we peered through the pond ice, a quick movement caught our eye. The students declared it to be an illusion because “It’s too cold for anything to be moving.”

And, then…an aquatic sowbug slowly ambled across the submerged leaves. We also saw a water boatman make a quick appearance before disappearing under a leaf.

The pond is alive even in winter.

When the water temperature is very cold, the metabolism of all the pond organisms slows. Many of the invertebrates, both adults and larvae, snuggle into the slightly warmer muck at the bottom. They avoid the formation of destructive ice crystals within their cells by producing an “antifreeze.” Water boatmen and backswimmer insects have been observed in masses in air pockets under the ice.

When the sun’s rays penetrate the clear ice, some plants are able to photosynthesize and put oxygen into the water. In addition, the slightly warmer temperatures kick start some metabolisms.  Organisms such as water striders, diving beetles, dragonflies, damselflies and even overwintering tadpoles to move about under the surface ice.