After blue-green algae bloomed on Cayuga Lake at unprecedented levels in late July, the potentially harmful species have disappeared for now, according to the New York State Department of Environmental Conservation.
This year the presence of the toxic algal blooms — taking the form of a smelly, green, floating slime — was confirmed for the first time in Ithaca and Tompkins County.
This bloom threatened swimmers, boat riders, fishers and families who use the lake for drinking water.
“The southern part of Cayuga Lake had not been impacted by these blooms in the past,” said Samantha Hillson, the public information officer at the Tompkins County Health Department.
Some of Tompkins County’s summer destinations — including the Ithaca Yacht Club, Taughannock Falls State Park in Trumansburg and Myers Point in Lansing — underwent temporary closures in late July when they were awash in murky goo before they reopened in early August, according to the DEC.
Meanwhile, at the northern end of Cayuga Lake, Cayuga County has been impacted by harmful algal blooms for the past few years — and even had to address concerns about the public water supply because the extent of the contamination was so far reaching, Hillson said.
Blue-green algae, also known as cyanobacteria, can be found in all bodies of water on earth, said Prof. Nelson Hairston, environmental science, who studies harmful algal blooms on Lake Honeoye, one of the Finger Lakes. But the combination of warm weather, stillwater and high nutrient runoff gives the algae perfect conditions to bloom into green, slushy scum.
Under these conditions, the algae then float and are blown by the wind toward the shore, he said, where they can accumulate against the shore and stink while it rots.
Besides the unsightly appearance of the harmful algal blooms, exposure to toxins that the algae sometimes produces can cause skin irritations, allergic reactions and even death to people, wildlife and pets, he said. Further, once the algae decompose, they can sink and use up a lot of oxygen, which creates dangerous conditions for fish.
The cause of the sudden appearance in Tompkins County remains unknown, but Hillson said the high rainfalls and warm temperatures in late July could have contributed to the anomaly.
After several rounds of storms that brought flash flooding and above-average rainfalls to Ithaca in the last week of July, the Tompkins County Health Department saw a sharp rise in the number of suspect blooms reported from individuals concerned about their beach wells and waterways being covered in suspicious goo.
“Then it cooled off,” Hillson said. “And we hadn’t gotten this much rain the past few weeks, so, after that, the reports of harmful algal blooms decreased.”
Hairston said there has also been a lot more farming in the Finger Lakes’ watershed, leading to increased nutrient runoff in the whole region. Agriculture, especially on big farms and concentrated animal feeding operations, gave a big nutrient pulse that was linked to the increase in algal blooms, he said.
Following reports of suspicious outbreaks on Cayuga Lake in July, the Tompkins County Health Department had issued warnings about the harmful algal blooms over the summer, with a plea for observers on public and private lakefronts to avoid exposure to untreated water.
The DEC’s laboratory tests confirmed the presence of harmful algal blooms and cyanotoxins, produced by the harmful algae, at various lakefronts on the lake’s southern end.
The health alerts — warning against swimming at Cayuga Lake and drinking untreated lake water — continued for two weeks from late July through early August.
Once tests indicated the toxic algae were absent, the warnings were lifted and closed locations reopened in August, the New York State Parks Recreation and Historic Preservation said.
While certain lakefronts and parks in Ithaca have not been issued any warnings or undergone closures, occurrences of harmful algal blooms are not rare throughout the Finger Lakes region.
Over time, the department has seen reports of algal bloom sightings steadily rise. So far in 2017 more than 60 waterbodies have gone on the list, and, as soon as an occurrence has been identified, the DEC has issued warnings to health departments, parks and private lakefront owners.
“It’s a problem in Cayuga Lake and we need to worry, for sure, but it’s also a problem worldwide,” Hairston said.
The Environmental Protection Agency stated in a report that warmer weather, higher carbon dioxide levels and more intense storms also contributed to increasing algal blooms across the United States.
“The documented occurrence of harmful algal blooms in the Finger Lakes has been increasing,” said Dr. Lisa Cleckner, director of the Finger Lakes Institute at the Hobart and William Smith Colleges.