East Hampton Waters Are (Almost) Fine
The water quality in bodies overseen by the East Hampton Town Trustees is generally excellent, according to a presentation at Town Hall on Monday, but algal blooms that can be harmful to shellfish, finfish, and humans remain a concern.
For the last two years, the trustees have funded water sampling, performed by Christopher Gobler of Stony Brook University’s School of Marine and Atmospheric Sciences, at sites including Napeague Harbor, Fresh Pond, Accabonac, Hog Creek, Northwest Harbor, Three Mile Harbor, and Georgica and Hook Ponds. On Monday, Dr. Gobler presented his findings from 2014 to an audience that included most of the trustees as well as Supervisor Larry Cantwell and Kim Shaw, the town’s natural resources director.
Surrounded by the Atlantic Ocean and Block Island Sound, strong tidal flushing and wave movement keeps East Hampton’s water quality high, Dr. Gobler said, as does the town’s distance from the metropolitan area. However, he said, development can cause impairments, “problems that trickle down marine ecosystems.”
Phytoplankton, or algae, is at the base of all aquatic food chains and therefore “incredibly important for controlling the productivity of marine fisheries.” But, Dr. Gobler warned, “sometimes there can be too much of a good thing.”
With the exception of Georgica Pond in East Hampton, tidal flushing maintains high salinity and oxygen levels in town waterways, he explained. In the pond, however, a bloom of cyanobacteria (blue-green algae) caused its closure for much of last summer, during which crabs and other marine life could not be harvested. Cyanobacteria can produce a gastrointestinal toxin called microcystin.
When the pond was opened to the ocean in October, Dr. Gobler said, the bloom shrank dramatically, while the natural flushing of the water raised oxygen and salinity levels.
While the overall oxygen level in East Hampton Town waterways was well above the State Department of Environmental Conservation’s standard and conducive to healthy fisheries, he said, levels at the head of Three Mile Harbor fell below the standard in August and early September, when the water was warmest. Poor water circulation and nutrient loading, such as nitrogen, were behind the drop.
High levels of alexandrium, or red tide, which has been “fairly widespread on Long Island in recent years,” were measured last year in Three Mile Harbor, Dr. Gobler said, and were lower than in 2013. When filter-feeding bivalves such as clams, mussels, and oysters consume a lot of this microalgae, they can accumulate toxins and be unsafe for human consumption. “We do have firm evidence,” he said, “that a high level of nitrogen-loading promotes these events and can lead to more areas being closed.”
Dinophysis also produces a toxin. “We knew it was on Long Island for a very long time, but just a few years ago we found that not only is the organism present but the toxins are getting into shellfish.” Dinophysis was found “everywhere, but the levels were quite low.”
Cochlodynium, or rust tide, was measured in Three Mile and Accabonac Harbors. While it does not pose a threat to humans, it is potentially lethal to marine life.
A trend revealed in the federal government’s national climate assessment in 2014 has important implications, Dr. Gobler said, and may be a signal of climate change affecting New York State. “In the last 50 years or so, the incidence of heavy rainfall events . . . is up by 71 percent,” he said. While the total amount of rainfall is unchanged, “that rainfall is typically happening all at once.”
Rain, he said, delivers nutrients and, potentially, bacteria from the land into the water, where it can impair water quality and accumulate in shellfish. High levels of fecal coliform bacteria were measured in Accabonac Harbor and Hog Creek in September, coincident with rainfall, Dr. Gobler said. The D.E.C. closes water bodies to shellfishing either seasonally or permanently if there is concern over fecal coliform bacteria.
Dr. Gobler is assembling a plan for water-quality monitoring in 2015.