Despite a massive die-off of bay scallops in the Peconic Estuary last fall, many waters under East Hampton Town Trustee jurisdiction, though by no means all, were of a high quality in 2019.
Christopher Gobler of Stony Brook University’s School of Marine and Atmospheric Sciences, who monitors multiple waterways under trustee jurisdiction, delivered an annual report to the trustees on Monday. It showed progress in reducing the nitrogen that feeds harmful algal blooms in Georgica Pond, but also showed other water bodies with high levels of chlorophyll and consequent low dissolved oxygen.
Dr. Gobler also told of a surprising development: two days of low dissolved oxygen levels and multiple spikes in chlorophyll in Napeague Harbor, where water quality is typically the highest of all bodies surveyed.
From April to November last year, Dr. Gobler and his team of researchers studied Napeague Harbor, Accabonac Harbor, Hog Creek, Three Mile Harbor, Northwest Creek, Wainscott Pond, Georgica Pond, and Hook Pond. At some locations, water temperatures were higher than previously recorded, he said. High temperatures are associated with low dissolved oxygen.
In January, the State Department of Environmental Conservation announced detection of a coccidian parasite in a sample of bay scallops collected from the Peconic Bays. That parasite “is promoted by environmental stressors on the organism,” Dr. Gobler said. “They only progress when the bivalve is already under stress,” for example by high water temperature.
Harmful algae concentrations in saltwater bodies were generally low last year, with the exception of blooms of rust tide (dinoflagellate cochlodinium) in Hog Creek and Northwest Harbor. Levels above the threshold for harmful effects on marine life were measured in Hog Creek, Dr. Gobler said.
Fecal coliform bacteria, which can contaminate shellfish beds, were measured at levels “about where we’d expect,” Dr. Gobler said, except at Hand’s Creek, where they were higher. Peak measurements in Accabonac Harbor, Hog Creek, Three Mile Harbor, and Northwest Harbor were also above the long-term average, he said.
Climate change is likely responsible: According to the Climate Reality Project, as the atmosphere warms, it can hold more moisture, and the rate of evaporation from the ocean increases. The higher rate of evaporation contributes to more extreme rain events.
“Some of this made sense when we looked at the rainfall data,” Dr. Gobler said. “The amount of rainfall we’re getting hasn’t changed yet, but the way it’s being delivered has, significantly.” Frequent moderate rainfall is giving way to “more and more singular events, delivering an inch or more at a time. Those events are more likely to be causing surface runoff in the water bodies.” Higher levels of fecal coliform bacteria, higher levels of chlorophyll, and lower levels of oxygen are related to these “very strong rainfall events.”
Three Mile Harbor remains “a hot spot for water quality impairment,” specifically within the head of the harbor, Dr. Gobler said. He blamed high nitrogen levels from wastewater. The surrounding land is heavily developed, and most properties, he said, are equipped simply with a cesspool or septic tank attached to a leaching pool. Though chlorophyll levels were generally low, multiple spikes above the federal Environmental Protection Agency’s 20 milligrams-per-liter threshold were measured in Three Mile Harbor. “Oxygen levels during the day are as high as they get,” but mean oxygen levels were low, which has been observed every year. “When you get the collision of a low tide that happens at night, that’s when you get these dangerously low oxygen levels,” leading to fish kills.
In freshwater bodies, cyanobacteria, or blue-green algae, bloomed in Georgica Cove, but at levels an order of magnitude lower, for the fourth consecutive year, than was measured in Georgica Pond from 2013 to 2015. Cyanobacteria levels were also low in Hook Pond. Wainscott Pond, however, experienced an intense cyanobacteria bloom for much of the summer. Dredging the pond, as mud is a big contributor of nitrogen and phosphorous, and installing a permeable reactive barrier — trench boxes filled with ground woodchips or another reactive substance that intercepts groundwater before it can seep in — are high priorities for Wainscott Pond, Dr. Gobler said.
Prior to his presentation, Mark Mendelman, an owner of Seacoast Enterprises, which operates marinas and boatyards on Three Mile Harbor, questioned whether eliminating nitrogen “is the most effective way to stop harmful algal blooms and restore a productive ecosystem.”
Bob Nuzzi, a former trustee, member of the town planning board, and marine biologist for the Suffolk County Health Department, also questioned the conventional wisdom about nitrogen. “Could we have an unintended consequence in reducing nitrogen to a level where we’re actually harming the ecosystem?” he asked.
There is no evidence to support the hypothesis that there is insufficient nitrogen to support fisheries, Dr. Gobler said. Rather, “There’s a wealth of evidence to show if you enhance the levels of nitrogen in an ecosystem, you stimulate the growth of harmful algae,” he said. “These toxins are nitrogen-rich compounds. When you feed the algae more nitrogen, they make more toxins. . . . That’s been proven many times here in Suffolk County, and it’s been proven globally as well.”
