Blue-green algae blooms plague Housatonic, while Candlewood sees relief

Photo of Katrina Koerting

Kettletown State Park closed to swimmers Aug. 6 and never reopened, evidence of the toxic blue-green algae that plagued beaches along the Housatonic River this summer.

“It’s worse now than I’ve ever seen it,” said Edwin Wong, a Western Connecticut State University professor who leads a sampling and testing program for blue-green algae, or cyanobacteria, at beaches on Candlewood Lake, Squantz Pond and Lake Zoar. The program launched last year in partnership with the Candlewood Lake Authority.

Wong said he became involved because he wanted to research what causes the bacteria to release the toxin, which can be harmful to both people and pets, especially at a genetic level, and what role is played by environmental factors.

Wong, whose team includes university personnel, college and high school students, gathers and analyzes samples weekly throughout the summer. Most beaches on Lake Zoar showed higher levels of toxins from blue-green algae than federal and state limits permit through much of August and early September, when testing ended for the season.

The state lowered the permissible level from 15 parts per billion to 4 parts per billion this year to follow the federal guidelines. But Wong said the levels would still have been high under the old standards. Many of the samples collected at the beaches on the Housatonic River had many readings in the high teens or low 20s.

“Once August hit, boom, everything shot up,” Wong said.

Although blooms were spotted last year on Candlewood Lake in Sherman and New Fairfield, toxin levels were low when tested.

This year, green streaks covered the water in small inlets at Eichler’s Cove and Kettletown, on the Lake Zoar shore in Newtown and Southbury. Wong said the test vials had visible clumps of the bacteria floating in the water samples.

“They were just loaded,” he said.

Wong and Ghada Hafez, the project’s lab manager, said more research has to be done to determine what causes the blooms and why the Housatonic River had more outbreaks than Candlewood.

Wong theorizes the mild winter, rainy spring and warm summer could have played a role.

“Everyone loves warmer weather, especially bacteria,” he said.

A milder winter also meant cold didn’t kill the bacteria, allowing them to lie dormant in the sediment until spring. Heavy spring rains could have washed fertilizer and other nutrients into the water sources, providing a food source for the blue-green algae.

Wong theorized Lake Zoar beaches experienced more blooms than Candlewood because the Housatonic River is fed by runoff from two states and there is more opportunity for pollutants such as phosphorus and nitrogen to be washed in and brought downstream.