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Hello Chilmark Pond Neighbors,

MV CYANO is a collaborative initiative among Island Boards of Health and scientists from Great Pond Foundation to monitor cyanobacteria on Martha’s Vineyard. Cyanobacteria, a.k.a. blue-green algae, are a group of microorganisms found in all Vineyard waters. When cyanobacteria grow rapidly or bloom, they can produce cyanotoxins, which when concentrated, can cause adverse health effects in humans, pets, or livestock who wade in or ingest blooming waters.

Cyanobacteria concentrations in the middle portion of Chilmark Pond are indicative of a growing cyanobacteria population that at bloom concentration and could pose adverse health risks based on samples taken on July 26th, 2023. This puts Middle Pond in the red, “ADVISORY” risk level, and triggers more frequent sampling and also cyanotoxin analysis. A sample has been submitted for cyanotoxin analysis. We will be in touch once the analysis is complete.

The Boards of Health have designated highly conservative risk levels: red means that levels of the algal species capable of causing toxic blooms are above the EPA Drinking Water standard. (In other words, just under these levels of toxin could be found in your tap water and you could safely drink it in your morning coffee.) The red risk level also means that, in addition to not letting your dog and/or toddler play in the water and possibly ingest it, (which is generally advised against at any time during the season when blooms are possible), the Chilmark Health Department advises against fishing (crabs, fish, shellfish) and/or eating catch from, or wading or swimming in Middle Chilmark Pond until conditions change for the better.

Should you have further questions about risk, please reach out to Chilmark Health Administrator, Anna McCaffrey. Should you have any further questions about the testing procedures, please feel free to reach out to me.

All the best,


Emily Reddington she/her/hers | Executive Director | Great Pond Foundation


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