top of page

Our Pond

Chilmark Pond is a strikingly beautiful coastal great salt pond located on the south shore of the island of Martha’s Vineyard in Chilmark, MA.  The Pond is segmented into three main basins: the Lower, Middle, and Upper Ponds (traveling from from east to west), with salinity varying from fresh to brackish as it flows eastward. The barrier beach south of the Lower Pond is breached several times a year by the Chilmark Pond Association, a riparian group authorized to oversee pond openings and closures to drain the pond and flush it with cool, clean, salty seawater.


The elevation and size (178-241 acres) of the pond fluctuates throughout the year depending on precipitation and time passing since the most recent breaching event. The Pond’s watershed is 3,500 acres. It is fed by two brooks: the Mill Brook feeds directly into the upper pond, Fulling Mill Brook feeds directly into the Middle Pond and both drain into the Lower Pond through Doctor’s Creek.


Once a thriving fish and shellfish habitat, Chilmark Pond is suffering from a host of ecological stressors both natural and human-caused. As a result, the Commonwealth closed its fishery decades ago and the Town of Chilmark has closed the Upper Pond at Lucy Vincent Beach to swimmers for years. The Commonwealth has designated the pond “impaired” due to it’s high nitrogen levels. 2020 marked the third consecutive summer of confirmed toxic cyanobacteria blooms, also known as blue green algae, in the Pond and the first time a recreational user reported serious symptoms consistent with cyanotoxin exposure. Periodic openings to the ocean help reduce pollutant loads but are insufficient to address the overall compromised health of Chilmark Pond. The Chilmark Pond Foundation (CPF) was established in 2018 to support the science-based restoration of the Pond’s ecological health and to protect it for future generations. 

MV CYANO is a collaborative initiative to monitor cyanobacteria in Chilmark, Tisbury, and Edgartown Great Ponds.  Cyanobacteria, also known as blue-green algae, are naturally occurring phytoplankton that have existed for millions of years. However, due to excessive nutrient loads and hotter summers, toxic blooms of cyanobacteria are occurring in Martha’s Vineyard’s ponds and throughout the world. When cyanobacteria grow rapidly or “bloom,” they can produce cyanotoxins, which can cause serious adverse health effects in exposed humans, pets, and livestock.

MV CYANO was developed through a collaboration of Island Boards of Health with scientific and financial support provided by the Chilmark Pond Foundation and the Great Pond Foundation.

To subscribe to our email newsletter and receive updates click here

Signage and Details

bottom of page