Vol. III No. 15 8/1/2022
by Charles Kenny MD
Stockbridge Board of Health
A few years back the Board of Health had to issue an advisory warning about a Cyanobacteria bloom on the Stockbridge Bowl. All sorts of havoc ensued, including rerouting the Josh Billings RunAground. The Board determined to do its best to prevent such an occurrence in the future, established a citizens' ad hoc committee to learn about Cyanobacteria, and subsequently asked the Select Board to put in place a testing program and preventitive plan, which was done.
Cyanobacteria are one-celled organisms, once thought to be algae, but they are more like germs - bacteria. Jargon terminology, like harmful algal bloom (HAB), perpetuates the original error. Like true plants, Cyanobacteria make oxygen using photosynthetic pigments, but the pigments are more primitive than those of plants. This is one of the testing means to look for Cyanobacteria. Other ways include sampling the water at different depths for oxygen and turbidity, among other things. Such testing shows the Stockbridge Bowl has huge numbers of Cyanobacteria all summer long, but they are very deep in the water, so they don't bother anyone. It is only when weather conditions cause the deeper waters to mix with the upper layers that Cyanobacteria can rise to the surface and become problematic because they can produce toxins. Generally, Cyanobacteria don't release these toxins into the water unless they die. Thus you can see a large colony on the surface of the water but testing the water for toxins comes up negative. Later, after the Cyanobacteria die, the visible evidence of the bloom disappears but the water can be full of toxin. This discrepancy can be confusing.
We have not had an HAB for a few years, but since we know Cyanobacteria are usually somewhere deep in the water.
In the next Issue of SU: Kenny will outline the procedures the Board and TriTown Health Department will take if a bloom should occur.
Photo: Patrick White