September 2017: Blooms of cyanobacteria closed Burlington beaches

Originally published Sept. 25, 2017.

Look before you leap: The recent shot of torrid beach weather has benefited cyanobacteria — an aquatic species that sometimes produces a sickening toxin.

Colonies of the scummy organism were responsible for closures of Burlington's North Beach and Oakledge Cove on Monday afternoon, as well as Texaco and Leddy beaches, according to social media posts from the Department of Parks, Recreation and Waterfront.

Blanchard Beach at Oakledge remained open as of 4 p.m. Monday — but staff were keeping area under close watch, they add.

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Most local beaches had been spared cyanobacteria “blooms” this summer, Lake Champlain Committee, a Burlington-based non-profit that monitors popular sites, reported last week. 

But colonies, or "blooms," have been common in parts of Missisquoi Bay, St. Albans Bay and particularly Lake Carmi in Franklin County, according to the committee.

In Lake Carmi, cyanotoxins were detected this past week at levels that are considered unsafe for drinking.

High temperatures in the next few days warrants continued vigilance throughout the region, state health authorities warn.

Cyanobacteria’s late September break-out isn’t unusual, although spikes normally take place in August, said Andrew Schroth, a research professor at University of Vermont.

The current run of warm, still weather — a contrast to this summer’s cool, windy spells — has contributed to “a perfect cocktail” for cyanobacteria, Schroth continued.

Reservoirs of nutrients on shallow lake bottoms, particularly phosphorus, are released more quickly when warm water, undisturbed by wind, is allowed to settle into stable layers, Schroth said.

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Zeppelin-like, cyanobacteria are able to move vertically through the water column, snagging phosphorus near the bottom and buoying up to the surface for a bout of photosynthesis, he added.

“Those conditions allow cyanobacteria to out-compete other organisms for nutrient and light resources,” Schroth said. “They can run with it, essentially.”

Decades-long attempts to reduce phosphorus flushing into water bodies from farms, timbering, roads and urban development show modest signs of success, according to models created this year by the U.S. Department of Agriculture’s Natural Resources Conservation Service.

Earlier this year, Gov. Phil Scott announced that cleanup costs for Lake Champlain could exceed $1 billion.

The struggle will likely be frustrated by natural processes. For the foreseeable future, lakes’ reservoirs of phosphorus (the legacy of centuries of runoff), combined with a warming climate, are likely to expand cyanobacteria’s growing season, Schroft said.

“They are carving out a niche that’s there because we created it for them in some of these systems,” he added.

Blue-green algae’s cocktail is indeed getting warmer.

In the early 1960s, Lake Champlain’s average surface water temperature in August was almost 7 degrees cooler than it is today, said Lori Fisher, executive director of Burlington-based Lake Champlain Committee.

The lake drains from a relatively large area, she added: “It’s the actions that we take on the land that influence the water quality; water quality here is really a reflection of our values; how much we want to invest.”

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So far, non-humans have invested very little time or energy in curtailing cyanobacteria’s growth, said Angela Shambaugh, a scientist with Vermont Department of Environmental Conservation.

Vermont lakes’ tiny aquatic predators, collectively known as zooplankton, have so far demonstrated no appetite for blue-green algae, perhaps, in part, “because it might be physically hard to eat,” Shambaugh, said.

Larger organisms like zebra mussels similarly turn up their noses — although researchers continue to keep their eyes peeled for potential blue-green algae gourmands, she added.

Contact Joel Banner Baird at 802-660-1843 or joelbaird@freepressmedia.com. Follow him on Twitter @VTgoingUp.