Burlington beaches reopened Tuesday afternoon after a closure caused by an extensive cyanobacteria bloom.
Burlington parks and recreation staff waited 24 hours after closure, as is standard practice, before testing the water for dangerous cyanobacteria toxins. The test results looked good, and the beaches were reopened.
“We’ve been dealing with the blooms for the past few summers so all the protocols and staff are in place,” said Deryk Roach, Burlington’s parks maintenance and operations superintendent. “It’s just business as usual as far as we’re concerned.”
Although sometimes harmless, cyanobacteria toxins can cause a variety of ailments from vomiting to liver failure. In very high concentrations, they can even be fatal.
Throughout the swimming season, from May 15 to Oct. 15, Burlington parks and rec staff members conduct visual checks at all the beaches at least twice a day, looking for the hallmark blue-green film created by cyanobacteria blooms. They also test the water for cyanotoxins multiple times a week.
Cyanobacteria blooms can last for extended periods of time, but rainstorms, like the one that passed over the area on Tuesday, can temporarily break up the blooms.
Cyanobacteria is a naturally occurring bacteria that lives in all sorts of aquatic environments and is usually harmless. The bacteria date back 3.5 billion years, making it one of the oldest species on the planet.
But when the right conditions strike, cyanobacteria cells rapidly multiply and form blooms, and those blooms can release harmful toxins. Like cyanobacteria itself, the blooms can occur organically.
But according to University of Vermont scientist Mindy Morales, climate change and human activity are increasing the frequency, duration and severity of the blooms, which can shut down recreation areas, poison drinking water, and cause generally dangerous conditions.
On Monday, standing on the shores of Lake Champlain, just south of Leddy beach, Morales filled a small plastic bag, like the type one would use to transport a goldfish, with Lake Champlain water. That water is usually slightly cloudy and a gray-blue color, but on Monday the water in her bag was bright green and filled with innumerable dark-green specks floating like dust suspended in a beam of light.
Morales took the sample back to her home, just a short walk from the lake, and, peering through her microscope, she examined a cluster of bright green and brown cyanobacteria cells in the water sample, finding that the bloom was a specific species called Dolichospermum lemmermannii that thrives in lower-nutrient lakes, like Champlain.
Everyone is at risk of cyanotoxin poisoning. However, the blooms pose the greatest danger to children, who are more likely than adults to ingest the water while swimming, according to the Centers for Disease Control and Prevention. Toxic cyanobacteria blooms are also hazardous to pets and livestock. Cyanotoxin poisoning killed two dogs swimming in a private pond in Stowe in 2019.
Over the past few decades, the amount of cyanobacteria blooms has skyrocketed across the world. In a 2019 study that sampled 71 large freshwater lakes across the globe from 1984 to 2013, the U.S. Geological Survey found that the intensity of summer algal blooms increased in over two-thirds of the bodies of water.
There are a few factors at play here, according to Morales. Using Lake Champlain as an example, she explained that, as winter ice decreases, the lake becomes more thermally stable, meaning that the water moves around less, which creates more favorable conditions for cyanobacteria. The generally warmer water doesn’t hurt either. Cyanobacteria don’t like to be too cold.
“Basically we’re seeing greater frequency and more intense storm events, more stable lakes, and warm water,” Morales said. “All of those things create good conditions for cyanobacteria.”
Beach closures due to cyanobacteria are not new to the Burlington area. But this is the first time that all the beaches closed simultaneously.
“It caught me by surprise that all the areas closed at the same time,” said Eric Howe, program director of the Lake Champlain Basin Program, a partnership of provincial, state and U.S. federal agencies working to improve the health of the Lake Champlain watershed.
Morales, however, was expecting blooms to arrive across Lake Champlain sometime this week. “One week ago, I saw a very small bloom starting, so I expected, after the rains and the stable hot weather, cyanobacteria blooms to appear,” she said.
Morales explained that a rapid increase in nutrients — which can be caused by runoff from heavy storms, like the one that swept through the area last Friday — followed by hot, stable weather creates the perfect conditions for cyanobacteria to multiply and turn into a bloom. So she wasn’t surprised when she went down to Killarney beach and saw that the water had been overtaken by a bloom.
Though cyanotoxins can cause a variety of adverse health effects, the federal government does not require it to be tested for in drinking water. Cyanotoxins are listed on the Environmental Protection Agency’s most recent contaminant candidate list of almost 100 known drinking water contaminants that are not regulated by the federal government.
While cyanotoxins are generally filtered out by conventional water treatment, according to the EPA, that’s not always the case. In 2014, high concentrations of cyanotoxins in the drinking water in Toledo, Ohio, which comes from Lake Erie, left almost half a million residents unable to use their tap water.
Although Burlington gets its water from Lake Champlain, public works officials say they are not concerned about cyanobacteria entering the drinking water supply.
“Our raw water intake is 4,200 feet’ offshore and 30-plus feet (depending on lake level) below the water surface, so at this point, we do not have significant concerns about cyanobacteria impacting our drinking water,” wrote Megan Moir, water resources division director at Burlington Public Works, in an email.
“However, with climate change and changing lake conditions, we are indeed starting to give long-term monitoring and mitigation a fair amount of thought,” she continued.
Additionally, Burlington’s raw and treated drinking water is tested by the Vermont Department of Health for the cyanotoxin microcystin, according to Moir. And public works has special water treatment systems that could remove those toxins.
Vermont’s cyanobacteria blooms are not limited to Burlington. According to the Vermont Department of Health, cyanobacteria blooms are present from south of Addison all the way to the Canadian border.
To find out about cyanobacteria blooms in your area or to report a bloom, check out the Vermont Department of Health cyanobacteria map.
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