Photos of the Long Island Sound

Research & Monitoring

Status and Trends: LISS Environmental Indicators

Hypoxia and Nutrients

Water Quality Index

The water quality index is a calculation that combines several water quality measurements to rate overall water quality in Long Island Sound on an annual basis. View Indicator

Western Sound Spring Bloom Chlorophyll a Concentration

Chlorophyll a is the green pigment in plants, and the concentration in surface water is an indicator of the amount of microscopic plants (called phytoplankton). This indicator is intended to characterize the spring phytoplankton bloom conditions in the western Sound each year. View Indicator

LIS Point Source Nitrogen-Trade Equalized Loads

This measure indicates the management effort to reduce nitrogen from wastewater treatment plants in order to meet state and federal water quality standards. View Indicator

Duration of Hypoxia

Hypoxia is a condition that occurs in bodies of water as dissolved oxygen concentrations decrease to levels where organisms become physically stressed and ultimately cannot survive. Duration of hypoxia refers to the number of days in a year during which hypoxia was observed in Long Island Sound. View Indicator

Area of Hypoxia

Hypoxia is a condition that occurs in bodies of water as dissolved oxygen concentrations decrease to levels where organisms become physically stressed and ultimately cannot survive. The area of hypoxia in Long Island Sound refers to the number of square miles in which dissolved oxygen concentrations were less than 3 mg/L over the course of a single year. View Indicator

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