A Look Into the State of the Long Island Sound

Water quality has been a hot-button issue lately — and some of the most damning evidence of a larger problem is in our own backyards.

On a recent fall day at Larchmont’s Manor Park, families walked along the water’s edge, boats were on their final sails of the season, and a few hardy boarders and kayakers at a dock put on wetsuits and grabbed their paddles. The quality of the water here is good — it gets a grade of B from the Beach Report Card, based on data from local health departments that is published by Save the Sound, a member-supported environmental-action organization.*

Yet only a couple of miles away on the same coastline in both directions, two Westchester County beaches are rated among the ten worst on Long Island Sound: Harbor Island in Mamaroneck is the worst overall, with a D grade, and Hudson Park in New Rochelle gets a C+. And only about a mile south of Hudson Park is Glen Island, which gets an A+, and is the highest scoring beach in Westchester. Why the big discrepancy in water quality over such short distances? “Pollution, like politics, is local,” says David Seigerman, Save the Sound’s clean water communication specialist.

“It’s hard for us to put a direct thumb on the exact things happening at those beaches, but we know that the Westchester coastline, as a whole, and the ground infrastructure, are having some challenges.”
— Peter Linderoth
Director of Water Quality, Save the Sound

There are 200 public and private beaches on the entire Sound — in the Bronx, Queens, Westchester, Connecticut, and Long Island — which local health departments monitor for Enterococci, fecal indicator bacteria that determines whether it is safe to swim.

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Glen Island is the highest scoring beach in Westchester, with a grade of A+ from the Beach Report Card.
Glen Island is the highest scoring beach in Westchester, with a grade of A+ from the Beach Report Card. Photo by Natalie Todaro.

One cause for bacteria is raw sewage, seeping from cracks or breaks in underground sanitary sewer lines. But the bigger risk comes after heavy rains, when stormwater seeps into the pipes; with more volume than the systems are designed to handle, these sewer overflows send untreated wastewater into the environment, which eventually flows to the beaches and other parts of the Sound.

Stormwater also picks up pollutants from surfaces in urban areas, like oil from roads and parking lots, fertilizer, pesticides and other chemicals, animal waste (both domestic and wild), and trash. “Stormwater causes a multitude of problems because it can carry so many different things,” says Laura McMillan, Save the Sound’s director of marketing. “It’s a problem for beaches, near-shore waters, embayments, and open water alike.”

Save the Sound’s Director of Water Quality Peter Linderoth points out that “Stormwater, itself, is not the pollutant.” He explains: “I try to think of it as more of the vector for everything it picks up and washes into the water.”

At Hudson Park in New Rochelle, says Linderoth, “We don’t know the exact source of pollution, but stormwater and old sanitary sewer infrastructure are two reasonable sources to consider. Wildlife can also contribute to high bacteria levels in the water, so it isn’t unreasonable to also consider geese on and near the beaches. Rats and racoons living in stormwater pipes have also been shown to cause elevated levels of bacteria in the water.”

Harbor Island is the worst beach on the Long Island Sound, with a grade of D from the Beach Report Card.
Harbor Island is the worst beach on the Long Island Sound, with a grade of D from the Beach Report Card. Photo courtesy of Save the Sound.

But at Harbor Island, with its near-failing grade, the issues seem to be not only stormwater pollution, but geography. Situated deep in Mamaroneck Harbor, scientists say there might be tidal restrictions where there isn’t enough exchange of cleaner water from the Sound. “It’s hard for us to put a direct thumb on the exact things happening at those beaches,” Linderoth says, “but we know that the Westchester coastline, as a whole, and the ground infrastructure, are having some challenges.” Nine of the 23 Westchester beaches in the report received top scores (which can be downloaded at savethesound.org/beachreport).

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Scientists say decades of nitrogen pollution from wastewater treatment plants, septic systems, storm-water runoff, and fertilizers depleted oxygen levels and contributed to toxic algae blooms, which imperiled species of fish, oysters, lobsters, and clams. But the EPA says infrastructure investments of more than $2.5 billion since the 1990s have improved wastewater treatment near the Sound in New York and Connecticut, and now almost 50-million pounds of nitrogen pollution are kept out of the Sound each year. This is helping many of those species to thrive again.

Save the Sound Laboratory Manager Elena Colon (right) demonstrates to seasonal staff how to prepare water samples for analysis in the seasonal bacteria-monitoring program at the John and Daria Barry Foundation Water Quality Lab in Larchmont.
Save the Sound Laboratory Manager Elena Colon (right) demonstrates to seasonal staff how to prepare water samples for analysis in the seasonal bacteria-monitoring program at the John and Daria Barry Foundation Water Quality Lab in Larchmont. Photo courtesy of Save the Sound.

And there have been some pleasant surprises: seals, dolphins, sharks, and humpback whales have been seen from the western Sound off Nassau County, north to Greenwich, CT, and beyond. This is not only because of cleaner water: The increase in the numbers of smaller fish, such as menhaden, which sharks and larger fish eat, and warmer water temperatures play a large part too.

But, warmer waters from climate change pose another problem. “Massive amounts of money were invested in reducing nitrogen coming from wastewater treatment plants,” says Linderoff, who runs Save the Sound’s lab in Larchmont that tests for contaminants in the bays and harbors. “We’ve seen significant improvements, but the warmer the water gets, the less oxygen it can hold, so climate change poses a very real threat…and threatens to undo some of the significantly positive change we’ve seen from reducing nitrogen.” Lobster populations, for example, have declined precipitously in Long Island Sound in recent years, in part because of warming waters, according to The Long Island Sound Study.

Overall, efforts to reduce pollution are working. “It’s still going to take a long time to recover,” says McMillan. “We’re on an upswing now, certainly, but we can’t get complacent.”

*Save the Sound’s most recent Beach Report Card is based on data from 2020–2022. Testing is done in both wet and dry weather conditions.

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