Joanna Moon/Sun Graphic Designer

August 30, 2021

Recurring Cayuga Lake Harmful Algal Blooms Point to Emerging Ecological Patterns

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Recognized by splotches of green spilling over the surface of water, harmful algal blooms have once again cropped up on Cayuga Lake — indicating worsening trends over the nearly seven years of the seasonal phenomenon. 

The Community Science Institute, a volunteer-led program that spearheads the testing and monitoring of harmful algal blooms in Cayuga Lake, reported this summer’s first suspicious harmful bloom on June 10, with the first confirmed bloom on June 30. 

But the toxic green streaks have continued to appear throughout the summer, with the most recent report of a harmful algal bloom on Aug. 26.

The blooms pose dangers for swimmers by causing skin or throat irritation, nausea, vomiting or diarrhea. These risks can be heightened for pets, such as dogs swimming in affected water, because they are especially impacted by the fast-acting nerve toxins that can be present in the water.

Taughannock Falls State Park, a popular local swimming spot, has been closed for swimming as of Aug. 30 due to the appearance of a harmful algal bloom.

According to Nathaniel Launer, director of outreach at the Community Science Institute, the harmful algal blooms are not actually made of algae, but are instead blooms of cyanobacteria. Although this bacteria is naturally occurring in bodies of water around the world, cyanobacteria produce toxins that can be harmful — and even fatal — to other organisms.

Known to be one of the first organisms capable of producing oxygen on Earth, cyanobacteria are microscopic organisms that evolved billions of years ago and get their nutrients through photosynthesis. 

“Certain conditions, like high amounts of nutrients in the water, warm waters and direct sunlight can help promote the growth of the cyanobacteria,” Launer said. “When the cyanobacteria undergo this rapid growth and form a bloom, these toxins can often be present in really high concentrations.”

Launer said the chemical compounds produced by cyanobacteria, such as toxins affecting the brain, and liver toxins such as microcystins, pose a public health risk to people who wish to swim or jump in for other recreational activities.

According to Prof. Robert Howarth, ecology and evolutionary biology, people and their pets should avoid Cayuga Lake waters if dense harmful algal blooms are present

Launer added that the blooms also threaten the natural balance of aquatic ecosystems by draining oxygen and nutrients from water, while also making water unusable by significantly reducing water quality. 

“When the water quality is impaired this way, it incurs a big economic cost — both a cost to tourism, but also a cost to … everyday life of having to deal with this issue,” Launer said.

Although the harmful algal blooms have been common for the past few years, Howarth said they are still a relatively recent phenomenon — the first hint of the blooms in Cayuga Lake was only in 2014. 

The toxic blooms also show a similar timeline across neighboring bodies of water in upstate New York, with Skaneateles Lake, one of the Finger Lakes close to Syracuse, experiencing its first documented bloom in 2017.

Since their initial appearance, the cyanobacteria blooms have hit every single Finger Lake, Howarth said, with the blooms getting more persistent.

“We see they’re a little bit worse in [the] short term, but I think the important thing to note is that they didn’t used to be with us, and now they are [a] recurrent and dangerous feature,” Howarth said.

Courtesy of Nathaniel Launer

However, according to Launer, it’s possible that improvements in the Community Science Institute’s tracking of harmful algal blooms could play a role in the apparent increase in harmful algal bloom reporting.

“It’s a tough question of whether harmful algal blooms are actually increasing, or whether we’re just getting better at identifying them and tracking them,” Launer said. “The answer is probably a little bit of both.”

There is no simple answer to the direct cause of the blooms. But as researchers have accumulated more data over time, trends have emerged that may point toward a specific hypothesis.

According to Howarth, the climate pattern of an extremely dry year, followed by an extremely wet year, could be a triggering event, as seen in the trend of 2016 and 2017. 

Howarth described that this “whiplash effect,” along with the intensification of nitrogen fertilizer usage in agriculture over time, could have led to the increase of nitrogen inputs to the lake. Howarth explained that as nitrogen builds up in the soil during the dry period, it then flushes into the lake during the wet period, promoting the growth of cyanobacteria.

“That [effect] could have been happening to some extent all along,” Howarth said. “But the weather extremes are getting more pronounced. And when we look at the monitoring data … it looks like these whiplash effects are much more common in the last 10 years than they used to be.”

Studies have shown that increases in the amount of nitrogen in the lake can play a role in the growth of cyanobacteria, as well as an increase in the production of the nitrogen-rich microcystin toxin, according to Howarth. The increase in toxins could contribute to the slowing death rate of the harmful microorganisms.

Launer added that warming surface temperatures of the lake and an increase in the frequency of intense storms could also contribute to the apparent increase in cyanobacteria growth.

Although the harmful algal blooms naturally disappear by the fall, there are currently no methods to mitigate the summer blooms once they happen. But for Launer, community outreach and education are the best way to prevent some of the possible negative consequences of the blooms. 

The Community Science Institute previously held public forums to discuss the water quality threat with community members, and distributed informational brochures across New York State parks to raise awareness, according to Launer.

“By learning how to identify [the] common appearances of harmful algal blooms, people can get really good at making decisions about when [it’s] not safe to swim, and just avoiding any exposure with these blooms,” Launer said.

For Howarth, further research on the causes of the harmful algal blooms is necessary to determine possible future prevention efforts. But in the face of insufficient funding and complex ecological dynamics, this research is no easy feat.

“Once you understand what the triggering mechanism is, it isn’t necessarily that you can just reverse it and go back to the way things used to be,” Howarth said. “[The blooms] could be changing the structure of the food webs in the lakes, for instance, in a way that puts you into [an almost] different environment … and we don’t understand that. It’s frustrating the scientists. It’s a real problem.”