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Water Quality Improves in Long Island Sound; Nitrogen Pollution is Declining

Release Date: 10/09/2014
Contact Information: John Martin, EPA Region 2, 212-637-3662,; Emily Zimmerman, EPA Region 1, 617-918-1037,

      Stamford, CT For the second summer in a row, concentrations of dissolved oxygen in Long Island Sound are higher than the long-term average, indicating improved water quality and improved ecological conditions for organisms that live in the Sound. Aquatic animals rely on oxygen that is dissolved in water to survive. When dissolved oxygen levels decline, this can cause some animals to move away, weaken, or even die. Low dissolved oxygen can occur when nutrients such as nitrogen enter a water body in excess, over stimulating plant growth. Nutrients such as nitrogen can enter a water body through discharges of sewage and from fertilizer runoff. In recent years, Connecticut and New York State have worked with the EPA to implement a nitrogen pollution reduction plan to improve the Sound’s dissolved oxygen levels, and to protect aquatic animals and public health. Much of the improvements in water quality is attributable to wastewater treatment facility upgrades and other measures are reducing nitrogen pollution to the Long Island Sound.

      “The work New York, Connecticut, local governments and the EPA have done to build and upgrade sewage treatment plants has significantly reduced the nitrogen going into Long Island Sound,” said Judith A. Enck, EPA Region 2 Administrator. “We need to make financial investments in sewage treatment plants, and work to reduce pollution from septic systems and fertilizers, which also degrade water quality in Long Island Sound.”

      "We hope the trend of improved dissolved oxygen levels in Long Island Sound continues. Investments in clean water are essential to a healthier ecosystem, which also contributes to more resilient and economically vibrant communities," said Curt Spalding, Regional Administrator of the EPA's New England office

      Every summer, levels of dissolved oxygen are reduced to a level that causes what is known as hypoxia, particularly in the western portion of the Sound and sometimes extending into central portions of the Sound. This happens when nutrients fuel the growth of algae blooms, and bacteria that then feed on the algae rob the water of oxygen. This hypoxia can be severe enough to force fish, crabs and lobsters to leave the area, and it can kill many species that cannot move away, such as shellfish.

      In 2000, Connecticut and New York State developed a plan that contains a nitrogen pollution budget, called a Total Maximum Daily Load, to reduce the daily discharges of nitrogen by more than 58% from levels discharged in the early 1990s. Connecticut has reached its nitrogen reduction target for wastewater treatment facilities and New York is expected to reach its target by 2017. In 2013, Connecticut and New York wastewater treatment facilities in the Long Island Sound basin discharged 35 million fewer pounds of nitrogen compared to the amount discharged annually in the early 1990s, primarily due to advanced wastewater treatment upgrades that employ technologies to reduce nitrogen.

      In 2013, the area of hypoxia was the third smallest since 1987. But in 2012, the area was one of the most severe years on record. While there is a general trend of improvement over the last decade, the difference between conditions in 2014 and 2012 highlights the high variability in hypoxia caused by factors such as temperature, wind, and precipitation.

      In addition to causing low levels of dissolved oxygen, high levels of nitrogen and other nutrients can have other harmful effects. Coastal wetlands that protect coastal communities against flooding can be degraded by high nitrogen levels. High nitrogen levels can also contribute to harmful algae blooms, which threaten aquatic animals and can threaten public health. Today’s announcement comes just two months after the city of Toledo, Ohio, issued a do-not-drink order to its residents after an algae outbreak caused by high nutrient levels that contaminated the city’s drinking water.

      The water quality information announced today comes from samples collected and analyzed by the Connecticut Department of Energy and Environmental Protection’s Long Island Sound Study Water Quality monitoring program, the University of Connecticut’s Long Island Sound Integrated Coastal Observing System, and the Interstate Environmental Commission’s Long Island Sound water quality monitoring program. The Long Island Sound Study provides funding support for each of these programs. To see a chart with the year by year measurement of the hypoxic area of the Sound since 1987, visit

      The Long Island Sound Study, sponsored by the EPA and the states of Connecticut and New York, is a partnership of federal, state, and local agencies, universities, businesses, and environmental and community groups with a mission to restore and protect the Long Island Sound. Visit for more information.