Cyanobacteria blooms often result in precautionary beach closures. The pea-soup-like blooms can release toxins hazardous to humans and animals, especially if ingested with lake water. But some towns and cities — like Burlington — are now using the state health department’s tracking system to instead keep beaches open for the visitor’s discretion.
A category two cyanobacteria spotting — which indicates a small bloom — would have led to a closure in previous years. Now, Burlington will keep the beach open with signage to let the public know the risk of choosing to go into the water.
A severe cyanobacteria bloom constitutes a category three rating, which still results in a beach closure.
Burlington’s beaches opted for full closures when the dangers of cyanobacteria were less-known, said Alec Kaeding, the waterfront manager with Burlington’s Department of Parks and Recreation.
“Since everybody was new to it, no one really understood it,” Kaeding said.
Now, Kaeding said, Vermonters have had years of coexisting with cyanobacteria under their belts.
“We've done a good job of informing people what it is and what it can do and what it can cause. Now we decided to switch to the state health department system,” Kaeding said. “And that way people can make their choice on a hot day, if we have like one small section of the beach that has cyanobacteria, to still use the other part of the beach.”
It’s a system they’ve adopted from Vermont state parks, in compliance with recommendations from the state health department.
During a category two cyanobacteria sighting, Burlington beaches still encourage families to keep young children and pets out of the water. This is because the water temperatures are warmest in shallow water along the beach, where children and dogs play.
Cyanobacteria thrive under warm conditions, along with high levels of phosphorus and calm waters.
Lori Fisher is the executive director of the Lake Champlain Committee, a nonprofit dedicated to the health of Lake Champlain.
“And temperature is a significant driver because many cyanobacteria like it warm and so as the water warms up, there's a greater potential for them to flourish,” Fisher said.
But the rainfall often experienced after heatwaves might put bloom growth on hold. The initial rain will cool down the water and storm wind could add chop to the surface, a combined effort with the potential to break blooms up short-term.
“But in the longer term, these intense storms are also bringing more phosphorus to our waterways,” Fisher said. “And so over time can be an influence as well.”
Because of all of these factors, cyanobacteria conditions can change pretty quickly.
Mae Kate Campbell is an associate scientist with the Lake Champlain Basin Program.
“From personal experience, I've been to a beach where it's been closed one day, and then the next day, everything's totally cleared up and it's open for swimming,” Campbell said. “And I personally will go in the water right after it's declared safe again, because I am aware of how dynamic those conditions can be.”
Effective cyanobacteria monitoring began on Lake Champlain in the 2010s, when the approach shifted away from water sampling in labs and toward visual observation by a team of volunteers.
“That was a real game changer in a way because it allowed us to really expand the breadth of cyanobacteria monitoring across Lake Champlain,” Campbell said.
Now, the observation reports are used to update Vermont Department of Health’s live Cyanobacteria Tracker.
Though warmer temperatures and more rain events pose questions about climate change’s correlation with the presence of cyanobacteria, Campbell said it’s too soon to tell.
“It's certainly something that's quite possible,” Campbell said, “but we're still kind of working out with historic observations and increasing our observations in the present day now so that we can get a better sense of the answer to that question in future years.”
The warmer temperatures have accounted for bloom sightings earlier and later in the season than expected, Fisher said.
“The period when we have the potential to see cyanobacteria blooms has extended,” Fisher said. “We had our first bloom report back in late May this year on Lake Champlain, and that's well before our official cyanobacteria monitoring program got started.”
Fisher says monitors start their observation season around June 16. And it’s not just early spring — though rare, cyanobacteria blooms have been spotted as late as November.
Experts say it’s important to stay cognizant of water conditions, both by checking reports from local beaches, but also in knowing how to spot a Cyanobacteria bloom.
The blue-green algae looks like pea soup spilled on the surface of the water. It can also manifest in confetti-like dots of the same substance.
You can report a cyanobacteria sighting on the Vermont Department of Health’s website where it will be reviewed and updated to the tracker.
The Vermont Department of Health recommends washing your body if you come in contact with a cyanobacteria bloom, which can produce toxins hazardous to humans and wildlife.
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