Courtesy of Don Sargent and Shannon Barrett

Harmful algal blooms in Cayuga Lake waters may cause risk to swimmers.

August 26, 2020

Harmful Algal Blooms Make Reappearance in Cayuga Lake This Summer

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In early July, the Tompkins County Health Department warned residents of the presence of harmful algal blooms in Cayuga Lake. Following the warning, Taughannock Falls State Park announced that it would be closed for swimming until blooms disappeared.

Taughannock Falls has since reopened, but there is no telling when harmful algal blooms may appear once again.

Algal blooms are a rapid growth period that allows the bacteria to be seen with the naked eye. They become harmful when colonies of algae grow uncontrollably and negatively affect humans and animals upon exposure. In the case of harmful algal blooms in Cayuga Lake, the blooms are actually cyanobacteria, not algae.

Although cyanobacteria and algae synthesize energy from sunlight, cyanobacteria are single-celled organisms while algae are multi-celled.

Health effects can vary, but possible symptoms of exposure to the cyanobacteria include vomiting, nausea, diarrhea, or skin, eye and throat irritation. Exposure includes both ingestion of the bacteria and physical contact.

“[It’s a] totally different type of organism — they’re photosynthetic but they’re bacteria,” said Prof. Robert Howarth, ecology and evolutionary biology.

The presence of cyanobacteria in Cayuga Lake is a new phenomenon, when the blooms were first recorded in 2015. Since then, blooms have reappeared every summer, causing beaches and state parks like Taughannock Falls to temporarily prohibit swimming.

“They shouldn’t have started [growing] in the Finger Lakes according to all of our theory,” Howarth said.

One hypothesis is that there has been an increase in nitrogen in the lakes, which allows the cyanobacteria to produce more toxins, and therefore prevents zooplankton predators from grazing on them, according to Howarth.

A drought period caused by climate change could allow nitrogen to build up in the soil surrounding the lakes. A subsequent season of rain could then flush the stores of nitrogen into the lakes, causing rapid cyanobacteria growth.

“We think there’s a big pulse of nitrogen that started the blooms … and that’s a result of climate change,” Howarth said.

The toxin that the cyanobacteria produces as a defense mechanism is called microcystin. Microcystin is not visible to the naked eye, so the presence of cyanobacteria should be taken as a warning that the toxin is also present in the water.

“The best thing to do is really just avoid [the cyanobacteria] to begin with so that you don’t have to worry about any of the negative effects,” said Samantha Hillson, a TCHD spokesperson.

If anyone does suspect possible contact, they should rinse themselves off with clean water. Dogs should also be rinsed, as their coats can pick up traces of the cyanobacteria. TCHD advises seeking immediate medical attention if any symptoms arise.

“It’s sometimes hard to know what is suspicious and what is a normal or non-toxic algae to be in the water … so we want people to know what to look for,” Hillson said.

Blooms can look like green streaks, clumps or blue-green paint on the water’s surface.

Cyanobacteria blooms typically disappear in the early fall due to colder lake temperatures and less sunlight. Currently, there are no known methods for preventing cyanobacteria growth or entirely eliminating them.

“In order to improve the management we need better science to understand what [the] change is,” Howarth said.