Last weekend a colleague of mine invited me to give a guest lecture for her summer class in evironmental and science writing at the Kellogg Biological Station. KBS is a research center built on the former estate of the Kellogg family (yes, the cereal people). It’s primary features are a campus of labs and greenhouses, along a large, very clear lake called Gull Lake.
Off campus there is also a bird sanctuary and any number of research forests and ponds (though I didn’t get to spend much time in these). I had only a little bit of teaching to do, so naturally I brought my equipment and my foldscope and spent evenings pestering lichen and tiny bugs with my hand lens, and looking at slides of algae.
The algae told me a story about the lake, one I couldn’t piece together until the next day. You see, most of the algae I see in my lake hunts are the thick, choking mats of spirogyra you find floating in artificial ponds all over city parks. They cover the top of the pond, tangled like a badly kept wig.
So why such a difference? I had a notion that I already knew part of the answer: there are waves on this lake. Spirogyra seems to thrive most where it can be stationary. It seems to need stagnant water. This lake is far from stagnant, but is instead clear and blue. But why should this matter to algae?
The students answered this for me the next day. Those ponds I see all the time are eutrophic, meaning they have a high biomass caused by a constant fall of rotting leaves and bird droppings. The algae I find there is better suited to a nitrogen rich pond. In the lake where there are currents and waves, these rock clingers do better.
And with that shift comes other forms of life. Zebra mussels (seen below), as well as new kinds of fish and flies.