Long Island Sound open waters show significant improvement while local bays continue struggling.

Save the Sound reported that 98% of the Sound’s open waters received an A, B or better for the second consecutive report card, underscoring the broad consistency of the improvement.
Of the 62 measured bays and harbors, only 56% earned an A or B. Specific declines included Oyster Bay, which fell from A-minus to B-plus; Middle Hempstead Harbor, which dropped from D to F; Huntington Harbor, which fell from B to B-minus; Inner Cold Spring Harbor, which declined from D-plus to D; and Northport Harbor, which declined from C to D.
The report’s grades were based on indicators including dissolved oxygen, chlorophyll or phytoplankton, water clarity and dissolved organic carbon, using data collected by Connecticut and New York environmental agencies and the Interstate Environmental Commission.
Save the Sound said localized pollution sources include nitrogen released from lawn fertilizer, vehicle exhaust along Interstate 95, septic systems and wastewater-treatment plants, in addition to stormwater runoff and sewer overflows.
Local restoration efforts are also underway: Friends of the Bay recently released 20,000 clams into Oyster Bay, aiming to help repopulate the bay and improve water quality over time.
Long Island Sound's open waters are getting cleaner. According to Save the Sound's 2026 report card, 98% of the Sound received an A, B or better grade for the second year in a row. The Western, Central and Eastern basins all earned A or A+ grades, while the Western Narrows achieved its first passing mark in 18 years, jumping from an F to a D.
The improvement stems from billions of dollars spent by Connecticut and New York on wastewater treatment and reducing nitrogen pollution. But the victory is incomplete. Local bays and harbors tell a different story — just 56% earned A or B grades, with several Long Island sites declining sharply in 2025, including Middle Hempstead Harbor, Huntington Harbor and Northport Harbor.
The Sound's main waters improved dramatically. Save the Sound graded the Western, Central and Eastern basins as A or A+, reflecting decades of cleanup work. The Eastern Narrows held steady at a B for the second year. The Western Narrows delivered the biggest surprise: it earned a D, marking the first passing grade in 18 years. Researchers measured dissolved oxygen, chlorophyll levels, water clarity and organic carbon using data from state environmental agencies.
Local bays tell a bleaker tale. Of 62 measured bays and harbors, only 56% earned A or B grades. Several Long Island sites declined sharply in 2025. Middle Hempstead Harbor dropped from D to F. Huntington Harbor fell from B to B-minus. Oyster Bay slipped from A-minus to B-plus. Inner Cold Spring Harbor declined from D-plus to D. Northport Harbor dropped from C to D.
These declines signal that localized pollution remains a serious threat. Save the Sound identified nitrogen from lawn fertilizer, vehicle exhaust from Interstate 95, leaking septic systems and wastewater plants as major culprits. Stormwater runoff and sewer overflows also degrade water quality in enclosed coastal areas.
Excess nitrogen is the enemy of bay health. The pollutant triggers algae blooms that choke marine life and reduce dissolved oxygen. Sources are scattered — septic tanks, road runoff, fertilizer on yards and golf courses. Unlike the Sound's main waters, which benefit from stronger flushing and circulation, bays trap pollutants. Local restoration efforts are underway: Friends of the Bay recently released 20,000 clams into Oyster Bay to help filter water and boost populations naturally.
Connecticut and New York have spent billions upgrading wastewater treatment plants and reducing nitrogen discharges into the Sound. This investment paid off in open waters, where oxygen levels and water clarity rebounded. Yet aging pipes still leak sewage during storms. Many septic systems in bay communities predate modern environmental standards. Save the Sound says closing these infrastructure gaps is critical to protecting bays and harbors from future decline.
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