Data Supports the Continued Health of Edgartown Great Pond

EGP has a vibrant and thriving ecosystem thanks to the data-driven management by the Town of Edgartown, the scientific monitoring and conservation by GPF, and the oyster restoration of the MVSG. The elevation of the Pond is on the rise as we head towards spring. 

The 2020 elevation of EGP is indicated in blue and the 2019 elevation is plotted in orange.

Data indicate that the current elevation of the Pond is about 3 feet above sea level as of this afternoon.  At this time last year it was >3.6 feet above sea level.  The Pond needs to be at least 3.5 feet above sea level for a successful cut. This means that flooding is not a concern and the spring cut will likely happen a few weeks later than it traditionally does.  Per Paul Bagnall, the cut is expected in the next few weeks. To prevent flooding, the goal is to cut the Pond before it reaches 4 feet above sea level.

In addition to elevation, it is also imperative to monitor the salinity of the Pond in order to protect its eelgrass ecosystem. Per the EPA, ideal eelgrass salinity is >20 parts per thousand (ppt). The eelgrass within EGP seems to tolerate salinity as low as 15 ppt, but has shown a decline in both health and distribution when the salinity drops to 10 ppt or below. The current salinity is within the healthy range for eelgrass and is expected to remain sufficiently high until the cut.

GPF is in the process of analyzing 2019 water quality data and will be releasing a report on the health of EGP in the coming weeks. EGP remains one of the healthiest salt ponds on the Island, but data indicate that with warming temperatures, further reduction in nitrogen entering the Pond will be necessary. Full details are coming soon. Please stay tuned.

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