Protecting & Restoring Long Island's Peconic Bays

Water Quality Overview and Threats

Excess nitrogen, low dissolved oxygen, harmful algal blooms, pathogens and toxic contaminants all threaten the water quality of the Peconic Estuary.

View of rust tide in the Peconic Estuary captured from a plane.

The Peconic Estuary ecosystem supports fishing, shellfishing, recreation, and tourism industries making the health of the estuary a vital part of the East End economy. As development continues to grow, the estuary is experiencing increased population pressure that fluctuates from 100,000 people to 280,000 people seasonally. This increased pressure and the accompanied land use changes have threatened the water quality, habitats and ecosystem services that the Peconic Estuary provides.

The most serious issue affecting water quality in the Peconic Estuary is excess nitrogen loading, which can cause harmful algae blooms, low dissolved oxygen, and degraded aquatic habitats. Pathogens and toxic contaminants also contribute to water pollution in the Estuary, and can make fish and shellfish unsafe to eat.

The most serious issue affecting water quality in the Peconic Estuary is excess nitrogen loading.

Poor water quality is tied to our actions on land. In the Peconic Estuary our primary pollution  source comes from many widely distributed sources– this is called non-point source pollution. Non-point source pollution is caused by the movement of water over the land surface (stormwater runoff) or through the ground- this water picks up natural and human-made pollutants, such as fertilizers, pesticides, motor oil, and human and animal waste, and  eventually ends up in lakes, rivers, wetlands, and coastal waters. The biggest sources of non-point source pollution in the Peconic Estuary is wastewater from residential on-site septic systems and cesspools. The second biggest source is fertilizer.

It is important that we understand the connection between human actions on land and the health of the Peconic Estuary.

This figure shows the land area that contributes groundwater to the Peconic Estuary, and the amount of time it takes for this groundwater to reach the estuary. The groundwater contains natural and human-made pollutants.

Learn More!

Nitrogen Pollution in the Peconic Estuary

Pathogen Pollution in the Peconic Estuary

Toxic Contaminents in the Peconic Estuary

Sources of Water Pollution in the Peconic Estuary

Long Island’s Aquifer 

Water Quality Updates


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