Why ponds freeze

This causes the water at the surface to settle to the bottom, pushing the now relatively warmer water at the bottom back to the surface. This process continues until the surface water cools below 4-degrees Celsius, at which point it becomes less dense, and eventually freezes.

Remember, water is most dense at 4 degrees Celsius. It becomes less dense above and below this temperature. If water were most dense as a solid, lakes would freeze from the bottom up, eventually freezing solid. In that case, little or nothing would survive in the lake. Most lakes and ponds don't completely freeze because the ice and eventually snow on the surface acts to insulate the water below. Our winters aren't long or cold enough to completely freeze most local water bodies.

This process of lakes turning over is crtically important to the life in the lake. It is these turnover periods that infuse and distribute oxygen throughout the entire water column. Fish have several adaptions to survive a winter below the ice.

Because warm water sinks in very cold freshwater, fish in these water bodies often gather in groups near the bottom. Some species, like koi and gobies, may burrow into soft sediments and go dormant like frogs and other amphibians, but most fish simply school in the deepest pools and take a "winter rest. In this resting state, fishes' hearts slow down, their needs for food and oxygen decrease, and they move about very little. If you've ever gone ice fishing, you know that a long line, a slow, colorful lure, and a hearty portion of patience are often required to land this quiet quarry!

This prompted me to think abo ut when and how our lakes freeze over in this area. As you all know, water freezes at 32 degrees Fahrenheit. Therefore, below freezing temperatures are needed for a week or more to form ice on a large lake.

As I have mentioned before, water is a unique substance in that the solid form ice is lighter than the liquid form water. For most substances, the solid form is heavier. Cold water usually has a good amount of oxygen dissolved in it, and any fish and wildlife will be using up less oxygen. If this is the case, aquatic life should be able to cope with the surface being ice capped for a few days.

However, if the surface stays completely sealed for more than a few days, you will need to act. The oxygen levels may start to fall, and dissolved waste gases may start to build up in the water. Overtime, this could be a deadly combination and will prove to be fatal to your aquatic life. This is especially a problem with a heavily stocked pond; where there is a lot of debris in the pond; or has snow lying on the ice, stopping light from reaching underwater plants.

If there is snow lying on top of the ice try to use a standard brush to remove the snow, as noisy methods can disrupt the hibernating fish. This will allow light to reach your aquatic plants, enabling them to oxygenate your pond. Keeping a hole open in the ice is a good idea to enable the gas exchange of Oxygen and Ammonia. As quietly as possible to avoid disturbing your fish, try melting a hole in the ice by placing a pan with boiling water onto the ice; this helps to melt it slowly without affecting the fish.