Last month, the Chilmark board of health issued its first red advisory of the summer, warning of harmful cyanobacteria in areas of Chilmark Pond, and urging people to avoid swimming or shellfishing in the vicinity of the blooms.
On Wednesday, the Chilmark board of health announced that most recent samples collected from Chilmark Pond indicated that the bloom has “spread through Doctor’s Creek and the Able`s Hill Crossing,” expanding the area where an advisory is in place.
Though the majority of the lower pond is in “a cyanobacteria alert,” the southwest corner nearest Abel’s Hill remains under the orange “watch” status.
In recent weeks, Cyanobacteria blooms, or blue-green algae, have been detected in other ponds — Tisbury Great Pond, James Pond, and at Mink Meadows, and most recently, Squibnocket Pond.
The findings have prompted health officials to issue harmful bloom advisories, indicated to the public by red signage onsite.
Cyanobacteria are a group of photosynthetic microorganisms that are among the Earth’s oldest, and are found all over the world, including in Vineyard waters.
They help generate oxygen in the atmosphere, and are one of the most diverse and abundant organisms on the planet. Most cyanobacteria cause no harm, but a few can grow rapidly, or bloom, and produce toxins.
According to the Great Pond Foundation, harmful cyanobacteria blooms in ponds are the result of rapid growth in single-cell algae and seaweed, which can be exacerbated by the introduction of excess nitrogen and phosphorus and increased heat.
When in higher concentrations, the blooms can cause adverse health effects in humans, pets, or livestock who wade in or ingest the water. The blooms can also suffocate marine life.
First launched in 2021, MV Cyano is a collaborative initiative between Island health agents and the Great Pond Foundation (GPF) to actively monitor the prevalence of cyanobacteria.
Data collected and analyzed weekly by scientists at MV Cyano is used to help town health officials determine when and where to issue public advisories.
Island boards of health recommend that humans and pets stay out of blooming waters because of the potential negative impacts of cyanotoxins, if present.
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Dog ownwers! Be aware that this is a potential danger for your pets. Our dog Coquina was recently shaking uncontrollaby, and violently ill for a day (and out of sorts for two days afterwards) after a visit to the south shore of Tisbury Great Pond, near Crab Creek, which is the outlet for Black Point Pond. he seems to have recovered well, but her symptoms matched those indicated for cyanobacteria poisoning.
Hi Tom, glad you mentioned that fact. This kind of thing happens in lakes up north too, and I’ve seen first hand the harm it does to dogs, and often fatal.