To flush out nutrients, Sesachacha is opened
ENVIRONMENT
BY PETER B. BRACE INDEPENDENT WRITER
Joining marine and brackish ecosystems early Friday afternoon, the town opened Sesachacha Pond to the ocean.

ROB BENCHLEY/The Independent Opening Sesachacha Pond to the ocean last Friday meant John Correia in his excavator digging a special Y-shaped cut through the barrier beach between the pond and sea. Correia dug one main ditch to the ocean with two branches headed into the pond. The first channel facing directly up the full length of the pond helped get as much water out as possible and the second he carved to the north so the north wind would help push the water out of the pond.

The first of three possible openings for this Quidnet pond went off smoothly at the deft hands of John Correia, who worked the controls of his excavator and dug a Y-shaped trench between the pond and the ocean.

The pond remained open to the sea Friday afternoon through early Tuesday morning when a low tide likely allowed the channel between the two water bodies to fill with enough sand to prevent further water exchange.

Town Biologist Keith Conant likes to keep Sesachacha open as long as possible to wash out nutrients from septic systems and fertilizers leaching into the pond. Those nutrients can eventually produce enough algae blooms to suffocate the pond as they decompose, using up dissolved oxygen in the pond.

"It's pretty good," said Conant of the opening. "From what I heard, it was open yesterday [Monday], so at least we got three days."

Strong north winds on Friday forced Conant to direct Correia to dig two openings into the pond - a wider one aimed directly up the length of the pond to get as much of the water flowing into the channel as possible to open it up. A second cut was made to the north to capitalize on the wind blowing the water toward the ocean. Before the main ditch to the ocean closed, said Conant, the north cut had remained open the longest.

The town opens Sesachacha and Hummock ponds in spring and fall to resalt, clean out and re-oxygenate them for several days to more than a week to keep them healthy enough to support species that depend on varying degrees of salinity for survival. In Sesachacha's case, that means a healthy range between 18 and 20 parts per thousand of salt in this pond to allow winter flounder, sea bass, blueback herring, American eels, oysters, soft-shell clams and various minnow-like fish to live in the pond.

When he is sure the pond is closed this week, Conant will take water samples in hopes of the pond's salinity being higher than it was before this opening.

"The salinity has decreased to 9.7 parts per thousand, which is half of what it should be for a saltwater pond and that's one of my primary indicators for determining the health of the pond," he said. "It should have a higher salt water content for all the species in the pond."

Two of these creatures, eels and herring, also depend on these bi-annual openings for their procreation. Blueback herring and American eels are fish species that spend significant portions of their lives in saltwater and freshwater environments. The American eel is a catadromous fish because it breeds in salt water and lives a majority of its life in fresh to brackish water. The blueback herring is classified as an anadromous fish for spawning in fresh water and living in salt water. In the spring, adult herring swim into Hummock Pond to spawn. Mature eels slither out to spawn in the sea. In the fall, the young herring swim into the Atlantic and adolescent eels wiggle into the pond.

To further boost salinity levels in this pond, Conant wants to open it again this summer in addition to its fall opening, usually in October.

"We might try to get the summer opening, but I don't know if we'll get the permitting to open that because there are conflicting species demands, so if we open the ponds in the summer it will have to be after the plover chicks have fledged."

Following years of court battles, Nantucket secured local control of its great ponds in October 1993 with a standing permit from the Department of Environmental Protection, allowing it to open its great ponds to the ocean as needed with

respect for state laws. I