Blue-green algae blooms in Lake Champlain have intensified with late summer heat. Rouses Point, Missisquoi Bay, and North Beach in Burlington all issued warnings last week, and scientists say the algae blooms may have triggered a fish kill several weeks ago in Missisquoi Bay.

On August 16, hundreds of dead fish including yellow perch, white perch and freshwater drum washed up on the shores of Missisquoi Bay and began to emit a foul odor.

They’ve since been cleaned up, and scientists are trying to figure out what caused the fish kill.

Renee Plamondon is a spokesperson with the Ministry of Sustainable Development, Parks and Environment in Quebec. She says her organization doesn’t know exactly what happened. “Maybe it’s because the water is too hot, maybe it’s because we have cyanobacteria.”

Breck Bowden is a professor of environmental science at the University of Vermont. He says it’s possible that high water temperatures, low water levels, and the presence of blue green algae contributed to the fish kill.

"We don’t have a lot of data that’s available but fish kills like this will sometimes occur when there’s a bloom of algae…Those blooms produce algal bodies that then die, and when they die they begin to decompose, that consumes oxygen that would otherwise be used by the fish, and so the fish don’t have oxygen to breathe basically and they suffocate and die."

Scientists say that fish kills like this aren’t highly unusual. They happen about once a year in Missisquoi Bay, particularly when the water gets warmer. But they are worried about phosphorus pollution and algae blooms. Here’s Breck Bowden:

"When you put together the forcings that are occurring on the land, the various ways that we use the land that are delivering phosphorus and have historically been delivering phosphorus to the lake and we see the regular recurrence of these blooms year after year where we did not historically have them—it does worry me that we’re seeing these fish kills under these conditions and other conditions that occur in the lake."

The fish kill comes just weeks after the Lake Champlain Basin Program issued a "State of the Lake" report detailing environmental health in the lake.

The Ministry of Natural Resources and Wildlife in Quebec is planning a new study of fish populations in Missisquoi Bay starting this month.