In New England, winters are cold enough to freeze the surfaces of ponds and lakes. But why doesn't the ocean freeze along the New England coast? And how do the animals that live in ponds survive when they freeze?
If you've ever visited a pond during the summertime, you were probably aware that you were not alone. The buzzing of insects, the croaking of frogs and the splashing of fish show that the pond is home to many living things. However, if you go to a pond in winter, you may think that the wildlife have packed their bags and gone on vacation for the holiday season. With the exception of a few animal tracks, the area may seem deserted. Where did the pond's inhabitants go?
First, ponds freeze from the top down, and rarely freeze all the way through. (Shallow ponds are more likely to freeze than deep ponds.) The layer of ice at the top of the pond protects the water underneath from the extreme temperatures and the wind.
Each animal has its own way of dealing with the winter cold. Many birds fly south in the winter. Certain ducks stay, and can be seen feeding in unfrozen water. Frogs and turtles burrow in the mud at the edge or at the bottom of the pond. Some may burrow under leaves onshore. There, they hibernate — or sleep — through the harsh weather. Their breathing and heartbeat slow, and their body temperature lowers to conserve energy.
Beavers spend the fall months gathering and storing their favorite greens near their lodges so that they don't have to search for food in the winter. Other small mammals such as muskrats, weasels and raccoons are active in the winter, scouring the edge of the ice for food underneath.
Other living things prepare for the spring. In the fall, some insects lay eggs that are tough enough to withstand the winter cold. When the pond warms up again, the eggs hatch and new life flourishes.
Do it yourself
Try this activity to see how salt water freezes in comparison to fresh water. Think about what this means for the animals that live in ponds compared to animals that live in the ocean.
- 2 small paper cups
- 1 tsp. salt
- 2/3 cup cold tap water
- level space in the freezer
Label one cup fresh water and the other cup salt water.
Place 1/3 cup of tap water in each paper cup.
Add 1 tsp. of salt to the cup labeled salt water.
Place both cups in the freezer in a level place for one to one-and-a-half hours
Check the cups of water. Break the ice in the fresh water cup. Is it frozen all the way through? Is the ice in the center of the water, the bottom of the water, or on the surface of the water? Might a pond freeze this way?
Did the salt water freeze? Chances are, the salt water is cloudy but did not freeze. We know that fresh water freezes at 32 degrees Fahrenheit. However, the mixture of water and salt needs much colder temperatures to freeze. This is why the ocean only freezes in very cold places, near land closer to the north and south poles.