Nutrients

The primary measures of success are to implement nutrient reduction actions established under Suffolk and Nassau counties’ nine-element watershed-based plans; establish nutrient reduction or protection targets for six priority embayments through Connecticut’s Second-Generation Nitrogen Strategy; and develop additional nutrient reduction and protection plans across the watershed to reduce impairments in Long Island Sound, including open-water hypoxia, and its embayments.

Status

Check back in soon as the Long Island Sound Partnership is currently assessing the 2025 data for the measures of success.

Nutrient inputs or loads come from land-based point and nonpoint sources. Unlike point sources, like wastewater treatment plants where the exact location as to where the pollution is coming from can be identified, nonpoint sources  are more complicated, as the exact location of the source is diffuse and harder to identify and control. Nonpoint sources include stormwater runoff, fertilizer applied to residential and agricultural properties, atmospheric deposition, subpar or failing onsite wastewater treatment systems, pet waste, and agricultural practices related to livestock or row crops.

Since 1985, the Partnership has had tremendous success in significantly reducing point source nutrients from wastewater treatment plants, and as a result water quality and oxygen levels have improved greatly in Long Island Sound. In 2001, the Partnership developed  A Total Maximum Daily Load (TMDL) Analysis to Achieve Water Quality Standards for Dissolved Oxygen in Long Island Sound . A TMDL is the calculation of the maximum amount of a pollutant allowed to enter a waterbody over a certain time period, or a waterbody-specific pollutant (nutrient) diet. The Long Island Sound TMDL set the responsibility to meet a 58.5 percent reduction, from a baseline of 59,000 trade equalized (see here for more information) pounds per day of nitrogen, for wastewater treatment plants. In 2016, the Partnership met its goal of achieving a 58.5 percent reduction in nitrogen loading from point source wastewater treatment plants. Additional efforts to reduce nutrient loading to Long Island Sound embayments include enhancements to stormwater general permits, public engagement, and implementation of nutrient reduction measures through watershed-based management plans and agricultural nutrient management plans to address the diffuse nonpoint sources of nitrogen and phosphorus throughout the watershed.

Although, great strides have been made in reducing point source nutrients, nonpoint source nutrients continue to impact water quality as evidenced by eutrophication, annual summer harmful algal blooms and hypoxia (low dissolved oxygen). The Nutrient Objective’s measures of success aim to tackle nonpoint sources and further reduce nutrients in the Long Island Sound and its nearshore embayments through effective and targeted planning, collaboration, and local action.

Challenges

Hypoxia still occurs in the western open waters of Long Island Sound as well as the Sound’s embayments (bays, harbors, covers, and other shallow coastal waters). The western Long Island Sound and the embayments tend to be surrounded by dense development which increases nutrient loading from nonpoint sources. As mentioned previously, it is challenging to identify the location of and control nonpoint sources.

Importance

Nutrient pollution has degraded many of coastal waterbodies, their ecology, along with human health, and the economy (EPA, 2024). To ensure the protection of the Sound’s water quality, habitat and wildlife, ecosystem services, and value, it is imperative to continue reducing nutrient loading. Nutrient reductions have and will empower coastal communities in the Long Island Sound watershed by supporting livelihoods, enhancing recreational activities, and providing an outlet for residents and visitors to appreciate the Sound’s beauty.