On Friday, August 4 we received word that three public beaches on Keuka Lake were closed due to the “presence of blue-green algae.” These closures were made by the NYS Department of Health and were based on their visual observation of likely blue-green algae blooms on the water surface. The DEC posted this information on their website stating the presence is “suspicious” (not “confirmed”) and based on a “visual report” (not a “lab sample”). There have been no positive identifications of cyanobacteria (the real name for “blue-green algae”). Samples may have been taken and shipped to DEC officials for official identification and confirmation.
That afternoon, I sampled water from various locations on the western side of the east branch of Keuka Lake including Indian Pine Beach, one of the closed beaches. I analyzed the water samples this evening, and my samples did not show any cyanobacteria. However, despite this apparent good news, it was doubtful that these samples would be positive (even if true) because of the relatively rough water conditions. Cyanobacteria blooms develop on the water surface in relatively calm waters. Well-mixed waters (rough, choppy) disperse the cyanobacteria blooms making detection very difficult. Today’s conditions were relatively choppy with waves.
While it is certainly possible that Keuka Lake has seen cyanobacteria blooms in the past few days, I want to stress a few facts. First, we simply do not yet know if the algae observed is cyanobacteria. We need to await the results from the actual water sample tests. Second, there are many different species of cyanobacteria, most are harmless while the others can pose health risks. Even those species that can pose health risks by the production and release of toxins do not always release toxins. As such, statements such as, “toxic algae was found in Keuka Lake” are not at all based on evidence.
If the test results do confirm that we have Microcystis (or similar) species of cyanobacteria in Keuka Lake there are a few important facts to keep in mind. These are naturally occurring species in Keuka Lake and most other lakes. It’s not necessarily the presence that matters but the quantity. The higher the density, the greater the chance of health issues. As I have reported in my “State of the Lake” presentations for the Keuka Lake Association over the past four years, we have found Microcystis many times in Keuka Lake but always at a very low density. Microcystis blooms tend to be relatively short-lived, especially if there is little “fuel.” Due to excellent watershed management, Keuka Lake has very low amounts of algal nutrients, especially phosphorus, the “fuel” that can power harmful algae blooms. Given this, we would expect any bloom events to be relatively short-lived and sporadic in location. The health effects of Microcystis exposure vary greatly depending upon the time of exposure, the concentration of toxins, and the individual.
As a rule of thumb, don’t go swimming in water that looks weirdly colored or “gross.” Bad cyanobacteria sits on the surface, and the more of it, the worse it could be. So, if the water does not look inviting, then don’t jump in. If you do, rinse off with clean water. Please follow all advice detailed by the Department of Health. Fortunately, common sense follows the science in these cases.
Looking for more information? These articles by Dr. Sellers originally appeared in the Keuka Lake Association's newsletters: