Save the Sound’s 2026 report card says water quality improved or stayed stable in all five open-water regions of Long Island Sound. The Western Narrows received a D, its first passing grade since grading began in 2008; the other regions earned A-range or B grades.
The Western Basin rose from A− to A, the Central Basin from A to A+, and the Eastern Basin retained A+; the Eastern Narrows remained at B.
The report evaluates measures including dissolved oxygen, chlorophyll, water clarity, dissolved organic carbon and aquatic vegetation. Save the Sound said reducing nitrogen entering the Sound has been a major factor in the improvements; excess nitrogen can fuel algae blooms and low-oxygen conditions that harm aquatic life. The organization warned that climate change, rising water temperatures and worsening stormwater runoff could threaten progress, and said further nitrogen reductions and investment in wastewater and stormwater infrastructure will be important to maintain results.
