The Chilmark Board of Health issued a cyanobacteria bloom advisory for Squibnocket Pond Friday after samples collected came back positive for the potentially toxic bacteria. It’s the first bloom reported this season in an Island pond.
With the advisory, health officials recommend against recreational activities like swimming, wading, and fishing, as well as drinking the water or consuming finfish or shellfish in the area.
Cyanobacteria, also known as blue-green algae, are a type of microscopic photosynthetic, aquatic bacteria. They are responsible for a lot of the oxygen on Earth, but an overgrowth, or a bloom, has the potential to produce cyanotoxins that can cause adverse health effects in humans and animals upon contact or ingestion.
“It is especially important to keep pets and livestock away from bloom locations, as they are more likely to ingest the water,” a release from the town said.
The Wampanoag Environmental Laboratory, which independently does water analysis of ponds, detected the bloom in the eastern cove of Squibnocket Pond by the Chilmark town landing earlier last week. Follow-up samples were collected Thursday and revealed that the bloom seemed to be isolated to the area. The lab shares detections with the town board of health, who have the authority to issue advisories and make suggestions of public health at recreational bodies of water.
MV CYANO, a collaboration between town boards of health and scientists from the Great Pond Foundation to regularly monitor cyanobacteria, also confirmed the bloom from samples collected Friday.
There are nine ponds that are monitored by MV CYANO: Squibnocket Pond, Chilmark Pond, Tisbury Great Pond, Watcha Pond, Edgartown Great Pond, Cracktuxet Pond, Seth’s Pond, James Pond, and Mink Meadows Road.
So far, this is the first cyanobacteria bloom detected on Island, Emily Reddington, biologist and executive director of the Great Pond Foundation, said.
Last year, the first bloom was detected in May in Mink Meadows, Reddington said. Blooms can be seen in May or June but usually pick up in July, she added.
Increased nutrients, such as nitrogen and phosphorus, warmer temperatures, and stagnant water can cause accelerated growth of cyanobacteria in bodies of water and produce blooms. Peak bloom season is typically from August to October.
It’s one of the oldest organisms on the planet, but when the environment provides certain conditions, cyanobacteria can bloom excessively, Andrew Jacobs, manager and environmental technician for the tribe’s laboratory, said.
Squibnocket Pond is relatively stagnant and has a low refill rate, and so increased rainfall can lead to more wastewater and fertilizer runoff, especially as systems are overloaded from increased construction and population growth, Jacobs said.
“As the season goes on, it may do worse,” he said.
After detection, advisories last at least two weeks because even after cyanobacteria cells die, the cyanotoxins they release can be at a peak, according to Reddington.
There is a lot of science on cyanobacteria in fresh bodies of water, however knowledge on blooms in brackish water, such as those on the Island, is limited, and so the Island is almost like a “living laboratory,” Reddington said.
