The last post talked about thermal stratification in your lake. I mentioned that in winter there’s a layer (a thin one) of cold water directly under the ice, and beneath that the slightly warmer – yet denser – water that makes up most of the lake’s volume.
Well, a week or two ago, the ice melted, and the wind’s action stirred that surface water in with the rest, so that the water temperature was fairly uniform from top to bottom. This condition is important because it allows the lake to, in essence, take a deep and restorative breath.
In this time when the lake is not yet stratified (with warmer water on top and colder water below, as in summer), wind and wave action can mix oxygen into the water. So if you imagine putting a drop of blue food coloring into a bowl and stirring, that in a sense is what happens with the oxygen in your lake – it is thoroughly and evenly mixed in. This is called the spring turnover.
Of course, oxygen is what the fish, snails, crayfish, plankton and all manner of creatures need to survive. That includes the microscopic creatures in the lake sediments that break down dead material that sinks to the bottom.
As the weather gets warmer, your lake is starting the process of stratifying for the summer – warmer water on top, cooler water below. Later on we’ll explore what this stratification means to the life under your lake’s surface.
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