DES: New cyanobacteria blooms identified on Lake Winnipesaukee

Chestnut Cove in Alton is under a cyanobacteria watch after a bloom was discovered there NH Department of Environmental Services—Courtesy
Published: 08-21-2024 3:07 PM |
There are two new cyanobacteria blooms on Lake Winnipesaukee, according to the state Department of Environmental Services. New warnings and watches were issued Monday afternoon.
A warning was issued for Wolfeboro in the area of Jockey Cove, and a watch is in effect for Alton in the area of Chestnut Cove after gloeotrichia blooms were identified there.
Gloeotrichia, a different form of bacteria than those behind blooms around the lake earlier this summer, is commonly observed at this time of year but may still pose risks to health, a statement from the Lake Winnipesaukee Association read Monday afternoon.
“Gloeotrichia is a different type of cyanobacteria, it’s a different taxa than we were seeing at the end of June,” Bree Rossiter, Lake Winnipesaukee Association conservation program manager, said Tuesday morning. “The taxa that we were seeing at the end of June is a cyanobacteria called dolichospermum.”
Gloeotrichia doesn’t tend to form surface scum like cyanobacteria seen around the lake earlier this summer, but can under the right conditions including water temperature, the amount of sunlight and the right nutrients available, Rossiter explained.
Lower densities of accumulation may appear like a “starry night” while higher accumulations on the surface of the water may appear like a “galaxy” and could pose an increased health risk.
Blooms of gloeotrichia on Lake Winnipesaukee are not uncommon toward the end of August, but those who intend to use the lake for recreation should remain aware and pay attention to water conditions.
“Gloeotrichia is very dynamic and will quickly move around the waterbody based on wind, wave and boat action,” a spokesperson for DES wrote in a message Monday evening.
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The bloom at Jockey Cove was described as including light-green surface ribbons and clouds of material accumulating along the shoreline. That bloom was reported as being about the size of a tennis court and was measured at a density of 1,562,500 cells/mL.
At Chestnut Cove, the bloom was described as being clouds of small dots in the water and was also about the size of a tennis court. That density of that bloom was recorded as being 50,000 cells/mL, according to DES. The message from DES noted the density was below but approaching the threshold for safe recreation and recommended people consider avoiding swimming or allowing pets into areas with visible gloeotrichia accumulation.
DES issues warnings when the cell density of a reported bloom is measured at 70,000 cells/mL or higher. Watches are issued when cell density is measured below that figure.
The waters where those blooms were recorded will be resampled by DES officials in one week, and warnings will remain in effect until the bloom subsides. DES asked local health officials to post cyanobacteria warning signs at all public access points to Lake Winnipesaukee in Wolfeboro. Health officials in Alton have not yet been asked to post signs because the bloom is still in watch status.
“NH DES will resample the locations where the warning is currently in place for Jockey Cove,” Rossiter said.
State environmental officials have received other reports of potential blooms and were working to sample areas including the Wolfeboro town docks on Monday night, though heavy rains experienced throughout the Lakes Region could have helped to dissipate the blooms.
Conservationists with the Lake Winnipesaukee Association were helping to get samples sent to Concord Tuesday from areas where they received additional reports of potential blooms. There were reports of potential blooms for Rattlesnake Island, Wolfeboro Bay and Long Island in Moultonborough.
Those out on the lake are encouraged to remain vigilant and take notice if the water does not look clear or if they notice small, brown, pom-pom shaped accumulation floating up and down in the water. People should perform a risk assessment before entering the water.
“I’m working with [NH DES] to get a sample for Long Island and Rattlesnake,” Rossiter said.