Our guest blogger for the day is Ted J. Rulseh, author of the new book A Lakeside Companion, an accessible guide that helps readers understand the magic of inland lakes—the life in, on, above, and around the water.
When you look out on your favorite lake, what do you see? Beautiful blue water? A place for a refreshing dip on a summer day? A surface on which to paddle a canoe or kayak? Favored spots to catch fish for sport or dinner?
Your lake is all this, but also much more. A lake is a fascinating living system, full of mysteries and things to discover, if you look closely. Here are six things you may not know about the world beneath the waves.
It all starts with the sun. That’s right, the walleye you fry up for supper owes its existence, first and foremost, to the sun. It’s sunlight that enables plants and algae in the lake to manufacture food through photosynthesis. The food these primary producers make forms the base of the lake’s food chain.
Your lake’s water is a thin soup. The water is the broth; the meat and vegetables consist of tiny organisms called plankton. The vegetables are the cells of algae that float freely in the water; they’re called phytoplankton. The meat is made up of small creatures, called zooplankton, that swim through the water, feeding as they go. They feed on the algae and in turn become food for fish in the very early stages of their lives.
Your lake has layers. The water is not a pool with a uniform temperature, at least not in the warm months of the year. As spring turns to summer, the lake separates into layers. Cold water lies at the bottom. Warmer water, being less dense, floats on top. The zone where warm water meets cold is called the thermocline. You can experience the thermocline by swimming out into fairly deep water, then doing a feet-first surface dive. When your feet reach a depth of about 12 to 15 feet, you will feel a sudden change from warm to cool. You’ve penetrated the thermocline. Click here to watch a video where you can learn more about lake stratification.
The waters are all connected. There are lakes, rivers, and the vast resource known as groundwater. These are not really separate entities. They are all part of the same system. The top of the groundwater is called the water table. In an important sense, a lake is a depression in the land that intersects and exposes the water table.
Your lake has a “skin.” You’ve seen the rounded shape of water droplets on a lakeside leaf. What gives that droplet its shape is something called surface tension—it’s as if the water had a very thin, invisible skin. That’s why the insects called water striders can skim across your lake’s surface on their long, spindly legs: The surface tension keeps them from sinking.
Making ice is hard work. Your lake can take a long time to freeze, even with a number of cold and wintry days and nights. Because of a property of water called the heat of fusion, it is eighty times harder to freeze a given volume of water than to lower its temperature by one Celsius degree. Put another way, a drop of water has to give as much energy to freeze as it would give up to lower its temperature by 80 Celsius degrees.
The closer you look at your lake, the more you’ll discover, and the more you will treasure and want to protect that natural wonder.
Ted J. Rulseh writes the newspaper column “The Lake Where You Live.” An advocate for lake improvement and protection, he lives in the lake-rich region of northern Wisconsin.