Cynanobacteria - "They're back!"

There were two big stories on Thompson Lake when we sampled last week (4/22/09). The first was that there were people fishing on the lake. This is perfectly legal and regulated, but there had been no fishing up to this point. More at: http://www.nature.org/wherewework/northamerica/states/illinois/press/press3965.html

The second eye-catching event was that the cyanobacteria that had “filled” the lake the year before was back. The green material floating in lakes is commonly called an “algae” bloom, even though in this case, they are technically not microalgae, but phototrophic bacteria. Last year, we started picking it up in early June. I’ve gotten confirmation from an algal biologist that the species genus name is Aphanizomenon. I supply a diagram.

Upon first glance, the cyanobacteria looks like small, cut-up grass leaves. Upon closer examination, you can see it is composed of individual filaments, and under the microscope can ascertain the heterocysts (specialized cells that “fix” nitrogen from the air) and akinetes (thick, dormant cells that resting/”surviving” cells). I post a copy of a picture I had taken last year.