Blue-green algae found in Chilmark Pond

‘No swimming’ posted while town awaits test results.

“Traces of blue-green algae caused by nitrification have been found in Chilmark Pond, so signage has been posted warning people not to swim.” -Kyra Steck

Traces of blue-green algae have been found in the Chilmark Pond, and the town will be conducting a special analysis to test for the presence of fecal coliform (E. coli) in and around the water.

Buck Goldstein of the Abel’s Hill Association said the last time the water was tested, it showed no signs of contamination. But there are special tests that need to be done in order to identify the blue-green algae that stems from excess nitrogen levels. The bacteria at issue are associated with fecal matter, as well as nitrification — both of which can result from septic tanks and agriculture.

Nitrogen can also come from landscaping activity. Both farming and landscaping utilize nitrogen-rich fertilizers, which can leach into stationary bodies of water and cause algal blooms.

Goldstein said that these types of blooms have been occurring for the past few years, and are “a sort of canary in the coal mine” of deeper issues with Chilmark Pond and other landlocked water bodies on Martha’s Vineyard.

“There is a broad-based coalition of people on the Island who are concerned about this issue, and are taking a variety of steps to prevent this from happening or getting worse,” Goldstein said. 

The Times asked Chilmark health agent Marina Lent whether, based on the E. coli findings in Tisbury Great Pond in November, Chilmark has considered dye-testing homes on the periphery of the pond in Chilmark.

Lent said in an email that E. coli can stem from many mammalian and avian intestines, not just human ones. 

“While a cesspool sitting in groundwater could definitely feed the pond with E. coli, the main hazard from septic systems when they work per design is nitrogen enrichment,” Lent said. “The standard Title 5 system is good at handling pathogens, but will release nutrients and pharmaceuticals, and persistent chemicals from commonly used household products.”

Lent told The Times that towns are not required to test for the algae, but if they have visual confirmation of some type of suspicious bloom, they are required to post “no swimming” signs and indicate the risk.

“Not all algae blooms contain the toxin, but it is important enough for public health to take a precautionary stance,” Lent said.

Signage has been posted at the Chilmark Pond, and Lent said strong and clear directions have been given to the Abel’s Hill Association regarding children and pets.

Lent said that skin contact and any kind of ingestion of the pond water should be avoided. “The algae bloom is irritating to the skin, and when you drink it, your stomach acids make the cells burst. That is when the toxin comes out, and why drinking it is so hazardous,” Lent said.

Lent said the warning signage will be posted for two weeks, or until tests indicate that the water is safe.

She said that labs are affected by COVID-19 because testing equipment and personnel are all “stressed to the max.”

“We don’t know enough about this particular bloom, but we do expect we will be seeing these more frequently with more global warming,” Lent said,

Anyone with open wounds, or with a compromised immune system or other vulnerabilities, Lent said, should avoid going in the water entirely.

“If you are young and healthy, maybe you could go through it, but you would want to rinse off right after,” Lent said. “This issue is very nuanced, with lots of complexities.”

With the approaching tropical storm, Lent said she is hoping the heavy wind and some rain will “go a long way” in speeding up the process of clearing the bloom. 



  1. Sorry to see this happening. Many causes, most caused by overpopulation of the island and the concomitant activities caused by this.

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