Photos of the Long Island Sound

Status and Trends: LISS Environmental Indicators

Type of Indicators: Health/Condition Response/Performance Socio-Economic Historical/Background

Hypoxia and Nutrients

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

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

Frequency of hypoxia

Frequency of Hypoxia

This map illustrates the frequency of occurrence of hypoxia in LIS bottom waters over the last two decades. It indicates what areas of Long Island Sound experience hypoxic conditions most often, and which are rarely affected. 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

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

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

Sediment Delta 15N

Delta 15N is a nitrogen isotope whose relative abundance in benthic sediment is used to determine the contribution of wastewater and sewage to total nitrogen. View Indicator

Increases in Population and Sewage

Clostridium perfringens, a bacterial spore found in sediments, is an indicator of sewage inputs and can be used to create a historical record of the magnitude of sewage input to the Sound. View Indicator

Sediment Organic Carbon Concentration Chart

Sediment Organic Carbon Concentration

Measurements of organic carbon concentration in sediment cores can be used to reconstruct a historical record of organic carbon in Long Island Sound. View Indicator

Sediment Delta 13C

δ13C is an isotope of carbon used as a proxy for hypoxia in this indicator, enabling the creation of a 1000-year historical record of bottom water conditions in Long Island Sound. View Indicator

 
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