Tracking Eelgrass Recovery in Edgartown Great Pond- Monitoring Begins in 2026!
After a sudden collapse in 2022, new eelgrass growth is offering hopeful signs for the future of this pond’s underwater habitat.
Recap: The Pond’s Eelgrass History
Eelgrass once formed the backbone of a thriving ecosystem in Edgartown Great Pond, sustaining marine life and enhancing water quality.
In 2020 and 2021, GPF partnered with the Massachusetts Department of Environmental Protection (MA DEP) to validate eelgrass mapping through aerial surveys, which occur every five years and require on-site verification. Among all south shore ponds surveyed, Edgartown Great Pond stood out, boasting hundreds of acres of eelgrass and widgeon grass along its coves and corners.
This once-thriving habitat collapsed abruptly. Between spring and fall of 2022, eelgrass meadows all but disappeared. Murky waters caused by excess nitrogen, reduced light at the pond bottom, and unusually low salinity from unsuccessful pond openings combined to make survival nearly impossible. Once lush underwater meadows vanished, leaving large stretches of the pond floor barren and threatening the pond’s ecological balance.
2025: The First Signs of Return
In 2025, our field team set out on a hunt to search for eelgrass within Edgartown Great Pond.
In June of 2025, we were encouraged by small signs of life. Strands of eelgrass in several regions of the pond pulled up with the boat anchor marked the first time since the spring of 2022 that eelgrass was observed. This hinted at the possibility that eelgrass had returned.
Our team went snorkeling in the areas that eelgrass had been pulled up. In these areas we observed scattered patches of eelgrass. While eelgrass coverage is still modest compared to historical levels, the presence of these rooted patches represents a meaningful step forward in the pond’s long-term ecological recovery.
2026: Signs of Stronger Return
The summer of 2026 brought even more encouraging signs for Edgartown Great Pond. Eelgrass has returned to several regions of the pond and appears noticeably more abundant than it was in 2025. We first saw the difference during our opening sampling run of the season, when new patches were visible from the boat and previously observed patches appeared fuller and more established. Later in June, during a recreational swim near Swan Neck, a team member discovered something especially exciting: an eelgrass meadow growing along the shoreline.
A New Monitoring Collaboration
The discovery of this meadow has opened the door to a new monitoring collaboration with SeagrassNet, a global network that tracks seagrass ecosystems using standardized scientific protocols. To begin this work, we established three 50 meter transects within the meadow, each marked by screw anchors that remain in place on the pond bottom. During monitoring visits, transect tape is run between the anchors, and our team uses quadrats to measure seagrass density, percent cover, canopy height, shoot count, and overall meadow condition.
GPF will conduct this monitoring three times each year, in spring, summer, and fall, to build a clearer picture of how the meadow changes over time. After each monitoring season, the data will be shared with SeagrassNet and contribute to a larger global effort to understand, conserve, and restore seagrass habitats. Locally, this work will help us document eelgrass recovery in Edgartown Great Pond, identify conditions that support healthy growth, and share the importance of this habitat with the community.
Thank you to Agnes Mittermayr, Abby, Phil Colarusso, and Alex Shure for making this monitoring possible, and capturing the beaty of this ecosystem!
Importance of Eelgrass
Improves The Pond Ecosystem
Eelgrass absorbs nutrients and traps sediments helping to improve water clarity. Eelgrass also stabilizes pond bottoms and reduces erosion.
Habitat for Marine Life
Eelgrass serves as a habitat for larvae, fish, shellfish, and countless invertebrates. A single meadow can support an incredibly diverse community.
Stores Carbon
Coastal seagrasses and wetlands remove carbon from the atmosphere and help to combat climate change. BLUE CARBON is the carbon sequestered by coastal marine ecosystems.
Read a recent Vineyard Gazette article by Daniella Freedman about how eelgrass in Edgartown Great Pond has helped maintained consistently low cyanobacteria concentrations this summer and high water quality. The article is available in “Read the Latest” on our Ponds in the News Page!
Check Out Other GPF News:
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2026 Eelgrass Monitoring in EGP
EGP 2026 Summer Update
GPF 2026 Board Changes
MV CYANO PUBLIC PRESENTATION
2026 GPF Events