Blue-green algae are causing problems on Lake Champlain and other lakes across Vermont. Blooms are appearing earlier and are more widespread than normal this year.
It’s not unusual for blue-green algae to appear in Lake Champlain in the summer, particularly when it’s hot. But what is unusual is for it to be appearing this early in the year.
"Often we’ll see those in middle to late July into August and into the early part of the fall," said Louis Porter of the Conservation Law Foundation. "This year, those kinds of blooms, the noticeable ones that people report and can see even from the shore were beginning even before the 4th of July."
One of the reasons for that is the large amount of phosphorous that went into the lake during last year’s floods. But according to Mary Watzin, a long-time researcher on Lake Champlain, the weather is playing an even bigger role.
"I think the most important factor this year in the early blooms is the really warm weather that we’ve had," Watzin said. "Blue-green algae really just thrive in that hot, dead, still kind of weather that’s been very, very, very persistent this year so that’s the most important factor."
Already this year, state and town officials have posted warnings about water quality, and even temporarily closed beaches at a number of spots in the Burlington area, in Mississquoi Bay, and at Kingsland Bay State Park. There have also been warnings about blue-green algae at Lake Memphremagog and Lake Iroquois.
"I believe that was the first time that Kingsland Bay, at least in recent years, has had to close its beaches," Porter said. "Blue-green algae has shown up around the park before but this is the first time it was significant enough to require them to shut the beach."
Not all blue-green algae blooms are toxic, but only testing can reveal which ones are toxic and which ones aren’t.
So far this year, researcher Mary Watzin says none of the blooms in the Burlington area have tested positive for toxins. But a sample taken from Mississquoi Bay just north of the Canadian border did. And that concerns people like Louis Porter of the Conservation Law Foundation.
"We’re really getting to the point where this is widespread enough and significant enough both in terms of where it’s found and how bad the blooms are that we need to start thinking about addressing it in more systematic ways," he said.
Until then, Porter said people and pets should stay away from areas where there have been bad blooms in recent days.