At first glance, the channel carrying rushing water from the Edgartown Great Pond into the Atlantic looks like it might be pulling the pond into the sea, but this tradition that dates back centuries is crucial to keep the brackish ecosystem thriving.
On June 8, the town of Edgartown used an excavator to open a channel between the pond and the ocean in a carefully timed environmental effort known as “the cut.” This exchange between nutrient-rich brackish water and cool, clean, salty seawater is essential for the pond’s resilience. The influx of saltwater increases the salinity, reduces the temperature, and refreshes the pond, maintaining water quality.
Emily Reddington, the executive director of the Great Pond Foundation, described the cut as “recharging and renewing the pond.”
An excavator is used to cut a channel in the narrowest portion of the barrier beach in order to first drain the pond and then flush it with saltwater from the ocean. Over the course of time, the tides begin to fill in the cut, and the barrier beach heals itself.
Long before excavators drove out onto the beach to open this channel, the Wampanoag Tribe dug it by hand, to connect the tides and support their fishery. This tradition lives on today; however, the process looks slightly different.
“Ponds are nurseries that are nutrient-rich, that are then exchanged with the ocean,” said Reddington. “Tidal influx sometimes brings in larvae; lots of organisms can be exchanged.”
Reddington also pointed out the importance of the cut in relation to species like herrings and blue crabs. When the channel opens during a cut ,it gives adult herrings a path to enter the pond and lay their eggs. Without the cut, they’d be blocked by the barrier beach and the larval fish would not be able to thrive. Similarly, blue crabs thrive in brackish waters, like that in the Edgartown Great Pond, especially after a cut, when the salinity rises from the ocean’s flush.
Typically the town cuts the pond three or four times a year, with one happening just three months ago, in March.
“It’s a really wonderful exchange of biology,” said Reddington. For the health of the pond and the life that it supports, the cut is vital.
