How’s Long Island Sound doing?

Very well on the east end. Not so great on the western portion, according to environmentalists and scientists who studied the health of the 110-mile estuary.

A “report card,” released Thursday by the Connecticut Fund for the Environment and its bi-state Save the Sound program, gave this coastal body of brackish water grades ranging from an A- to an F for water quality.

The estuary — stretching from the East River in New York City to Orient on Long Island — was divided into five subregions.

The eastern section, from Westbrook to Stonington in Connecticut and Northville to Orient on Long Island, received an A-. The water quality gets progressively worse moving west, ending with the Western Narrows — from Manhattan to the Bronx and Sands Point on Long Island — which got an F.

The other three subregions — east to west — received a B+, B, and a C- respectively.

“This is a good report card to have so we can have a complete understanding of the challenges we need to work on,” Rep. Joseph Crowley (D-Queens) said at Thursday’s gathering at the World’s Fair Marina in Flushing, Queens, to make the results public.

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The annual report, issued for the second year, helps to guide government policymakers at the federal, state and local levels as they work to improve the health of the Long Island Sound. It also creates a benchmark and helps environmentalists track and measure the quality of the water in the Sound over time.

The report looked at four indicators — dissolved oxygen, nutrients, chlorophyll and water clarity — to see if each met the desired level of quality.

The problem seen across the Long Island Sound is excess nutrients, particularly nitrogen, which comes from wastewater, septic systems, fertilizer and fossil fuel burning, said Tracy Brown, director of Save the Sound’s New York office. Excess nitrogen leads to harmful algal blooms, a lack of oxygen in the water and a loss of vegetation in coastal marshes that buffer the area from the impacts of severe waves and flooding during storms.

However, Brown noted recent upgrades made to wastewater treatment plants to reduce the amount of nitrogen in their effluent are beginning to show benefits.

“Investments in infrastructure do bring dividends,” Brown said. “You pay and make the investment, and you’re going to get better water quality.”

Save the Sound, which has offices in Mamaroneck and New Haven, Connecticut, is embarking on an ambitious initiative to assign similar grades to the approximate 110 harbors and bays that ring the Sound.

Even though a stretch of the Sound is healthy, harbors and bays in that section may experience stresses such as low oxygen, she said.

“We’ve seen fish kills recently in Centerport Harbor and Peconic Bay,” Brown said.

The group has started to design a study, called the unified water study, that will enlist the help of citizen and community groups to gather data and monitor the water quality.

“We’d like to have a group in every bay and every harbor around the Sound that is testing water following this protocol . . . And, it really takes everyone to make that happen,” Brown said.

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Save the Sound will provide funding to defray some of the data-gathering costs.

Two Long Island groups — Coalition to Save Hempstead Harbor and Friends of the Bay in Oyster Bay — have secured funding, Brown said. Save the Sound is in discussion with the Setauket Harbor Task Force.