Milton Harbor received a D+ grade in Save the Sound’s 2026 Long Island Sound report card released Tuesday.
Making its debut on the biennial report card, the harbor in Rye received one of the lowest grades on the entire Long Island Sound. Grades measure the ecological health of bodies of water and how well they can support sustainable aquatic life, based on water quality data collected during the 2025 monitoring season.
Each of the 62 bays in the report were graded on five indicators: dissolved oxygen levels, chlorophyll, water clarity, seaweed accumulation, and oxygen saturation.
The biggest dings to Milton Harbor’s grade were an F in water clarity and a D in seaweed accumulation. Although seaweed is common in healthy saltwater systems, excessive accumulation indicates excess nitrogen pollution, which can harm environmental health.
“The more nitrogen that goes into a bay or harbor, the lower the dissolved oxygen is going to be,” said Peter Linderoth, Save the Sound’s director of healthy waters and lands. “So, a very good way to improve a score is to reduce those nitrogen sources, which includes fertilizer applications.”
Three other Westchester County harbors received grades Tuesday. Larchmont Harbor, also making its debut in the report, was given a C; Mamaroneck Harbor a C+; and New Rochelle a B-.
Save the Sound officials said runoff from the Blind Brook is a major contributor to Milton Harbor receiving a lower grade than neighboring bays in the county.
“One reason it was important to add Milton Harbor to the report is we know from studies and other scientists that fertilizer is a big challenge for Westchester County,” said David Siegerman, communications specialist for Save the Sound. “People love their green lawns. They aren’t naturally that green. They’re treated to look that way, and that becomes a real challenge for the water quality.”
Only eight of the 62 bays that were monitored received a worse grade than Milton Point: Wequetequock Cove (F), Inner Norwalk Harbor (F), Inner Eastchester Bay (F), Westchester Creek (D-), Bronx River (D), Inner Little Neck Bay (D-), Inner Cold Spring Harbor (D), Northport Harbor (D).
Roughly half of all bay segments (56%) received an A or B grade during the 2025 monitoring season. Leading challenges to water quality are dissolved oxygen (50% of all segments received a C or lower), chlorophyll (48%), and water clarity (47%).
Since Save the Sound’s unified water study began in 2017, Linderoth said he’s seen several grades either improve or worsen based on actions taken by communities. He said both large-scale municipal projects and individual residents can impact the cleanliness of harbors.
“Homeowners can pull back on how much turf grass they have in their yards, planting native, and you could go a step further by reducing stormwater,” Linderoth said. “Installing a small rain garden or even a rain barrel that catches the rain from their roof, that can then be used at a later time to water planting beds. Anything that reduces stormwater’s direct runoff into, in this case the Blind Brook, which then goes down into Milton Harbor, has the potential to raise the score as well.”
The report card also grades the five open water segments of the sound, based on four water quality indicators. Rye falls in the Eastern Narrows segment, which received a B grade. The three segments east of Rye all received an A, and the Western Narrows, near New York City, received a D.
“It takes time for a bay to recover, or to decline in some cases, when we talk about environmental health,” Linderoth said. “So, we’ll continue to track those trends. There are hyper-local actions being taken across the sound, and the report card is in a perfect place to show those improvements as more and more nitrogen is reduced and water quality conditions improve.”
Read the full Long Island Sound report card below:
