Waterways: How’re We Doing?

Christopher Gobler of Stony Brook University’s School of Marine and Atmospheric Sciences, who for the last three years has led a water-quality monitoring program for the East Hampton Town Trustees, will lecture on the ecological health of local waterways on April 18 at 6 p.m. at East Hampton Town Hall. The program, hosted by the trustees, will also include a talk by Barley Dunne, director of the East Hampton Town Shellfish Hatchery, on its efforts to seed waterways with native shellfish. An interactive dialogue will follow.

In 2015, Dr. Gobler tested 17 town water bodies, including Napeague, Northwest,  Accabonac, and Three Mile Harbors as well as Fresh Pond in Amagansett, Hog Creek in Springs, and Georgica and Hook Ponds. Last year, Dr. Gobler delivered a largely positive 2014 report, calling the quality of trustee-managed water bodies generally excellent. Surrounded by the Atlantic Ocean and Block Island Sound, he said, strong tidal flushing and movement keep East Hampton’s water quality high, as does the town’s distance from New York City.

 However, a notable exception was Georgica Pond, which, in 2015, experienced a second consecutive year of dense cyanobacteria, or blue-green algae. In both 2014 and 2015, the bloom, which suppresses oxygen and salinity levels, prompted the trustees to close the pond to the taking of crabs and other marine life for much of the summer. The trustees have opened the pond to the Atlantic Ocean on a biannual basis, after which its oxygen and salinity have returned to normal levels and the blooms have dissipated. The East Hampton Town Board and trustees are now pursuing renewal of a State Department of Environmental Conservation permit to the pond; dredging, coupled with the twice-yearly opening, would maintain higher salinity levels for longer periods.

Cyanobacteria blooms were also detected last year in Fort Pond in Montauk, Wainscott Pond in Wainscott, Agawam Lake and Mill Pond in Southampton, and Maratooka Lake in Mattituck. In the summer of 2014, oxygen levels at the head of Three Mile Harbor fell below the State D.E.C.’s standard, with poor water circulation and nutrient loading, such as nitrogen, behind the drop. High levels of alexandrium, or red tide, were also measured there. When filter-feeding bivalves such as clams, mussels, and oysters consume a lot of microalgae, they can accumulate toxins and be unsafe for human consumption. Cochlodynium, or rust tide, was also measured in Three Mile and Accabonac Harbors in 2014. While it does not pose a threat to humans, it is potentially lethal to marine life.

Officials from the town, East Hampton Village, and the trustees have identified excessive levels of nitrogen and phosphorous as a hazard to water bodies’ ecological health and fisheries habitat, and with groups including the Nature Conservancy and Friends of Georgica Pond Foundation are in the early stages of developing a mitigation plan.

Macroalgae is to be harvested from Georgica Pond this summer to determine if that is an effective mechanism of removing nitrogen. Other actions could include the installation of a permeable reactive barrier, a device comprising trench boxes filled with ground wood chips. Such a barrier was tested at Pussy’s Pond in Springs with promising results, and the town plans to install more at Three Mile and Accabonac Harbors.