Wet June Fuels Late July Cyanobacteria Blooms On Lake Champlain

Aug 3, 2015

Potentially toxic cyanobacteria blooms were present up and down Lake Champlain during the last week in July, according to a report from the Lake Champlain Committee. Data from the Vermont Department of Health show that liver toxins were present in St. Albans Bay that week as well.

The committee received 120 reports from 97 locations on Lake Champlain throughout the week, the report said. St. Albans Bay, Missisquoi Bay, Burlington and Shelburne all had blue-green algae alerts last week. In Port Henry, New York, officials closed public beaches last week because of algae.

“The same weather that made us want to dive into the lake to cool off provided favorable conditions for blooms in several areas of Lake Champlain,” said Lake Champlain Committee Executive Director Lori Fisher in a weekly update.

“Alert level conditions were reported in the main lake, Missisquoi Bay and St. Albans Bay during the week,” the update said.

Lake Champlain Committee Staff Scientist Mike Winslow says the July blooms could be more severe because of the heavy June rains.

“The immediate rainfall doesn’t affect it so much, but rainfall previously in the spring does have an effect,” he said. “Some folks out in the great lakes think that there’s about a six week lag time between rainfall and associated nutrient loading with rainfall and the blooms occurring in the summer.”

Using that timeline, cyanobacteria blooms through late July and early August may be linked to spring rains. But Winslow said the relatively drier July doesn’t mean conditions will improve on the same six-week timeline. The phosphorus – which causes the blooms when there’s too much of it in the water – is already there.

“The end of the summer always tends to be worse. It’s that complex interplay of factors,” he said. “The water’s going to get warmer as the summer goes on and that may be more important than the immediate rainfall. The nutrient loading just needs to provide enough, and there are enough nutrients out there, so then you need the other conditions – the absence of wind, the presence of warm water – to really drive the blooms. So I wouldn’t go so far to think that they might end. It just means that they started a little bit earlier than usual.”

According to the Vermont Department of Health’s online Vermont Blue Green Algae Tracker, there are “High Alert” levels in Phillipsburg, Quebec, St. Albans Bay and at the Button Bay boat launch.

In St. Albans Bay, the state detected Microcystin - a liver toxin - at a concentration below the "Vermont Guidance value" for recreational waters during the week of July 27. All state-run tests of drinking water supplies coming from Lake Champlain found no cyanobacteria-related toxins during the same period.

Winslow also said the area around Burlington has been harder hit by cyanobacteria blooms this year than usual.