New: ‘Sound Health 2010’ outlines health of Long Island Sound

Jan 19th, 2011 | By | Category: Long Island Sound, Pollution, River, Stormwater Runoff, Water, Water Conservation, Wildlife

Many look forward to reports published by The Long Island Sound Study to see how we’ve been doing when it comes to Long Island Sound and its watershed. The Long Island Sound watershed made up of 16,000 square miles – an area eight times the size of Delaware. Long Island Sound’s watershed covers all of Connecticut and parts of New York, Massachusetts, Rhode Island, Vermont, New Hampshire, and a small portion of Quebec. It is estimated that 8,000,000 people live within Long Island Sound’s watershed so human impacts are high.

Sound Health 2010, looks back at environmental conditions in the Sound and its watershed over the last two years and compares them to conditions from the last 20 to 30 years (a separate biennial report, Protection and Progress (pdf), details the management actions taken to improve the Sound).

“The densely populated and developed western basin, which includes ‘the Narrows,’ a narrow section connecting with the East River, is the most stressed, with fair water quality the majority of the time, and with sediment conditions rated as poor for half of the basin area,” according to the report.

Water quality improves moving eastward. The central basin has good water quality conditions more than 50 percent of the time, and the eastern basin has good conditions more than 80 percent of the time. Sediment conditions also improve in the central and eastern basins. The gradient in conditions from west to east refects the decrease in development and human population density between basins. In the lands comprising the western Long Island Sound watershed, 44 percent of the area is developed compared to nearly 20 percent in the central watershed and 16 percent in the eastern watershed. An increase in development indicates the potential for more pollutants to be fushed from hard surfaces such as roads and parking lots into storms drains that connect to tributaries and the Sound. The higher population also contributes more sewage to wastewater treatment plants and septic systems, and more vehicle emissions that deposit air pollution into the Sound.


In the Sound, hypoxia occurs mostly in the summer months and usually in the western basin and narrows. From 1987 through 2010, the maximum area of hypoxia averaged 195 square miles—an area about nine times the size of Manhattan, according to the report. The area of hypoxia has been below average for 11 out of the last 15 years. The summer of 2010 was the third least severe year of hypoxia since 1987, with hypoxia affecting 101 square miles. The duration of hypoxia in 2010 was 40 days, the fourth shortest duration since 1987, and 14 days fewer than average.

Also noted in the report:

  • Scientists and resource managers are seeing changes in species population as a result of warm temperatures.
  • Municipalities and state and federal agencies are using climate change projections to map what future conditions might look like on the coast as a result of climate change.

Sound Health reports that from 1980 to 2006, the population in the New York and Connecticut portion of the Sound’s watershed increased from 6.3 million to 7.2 million (the population of the entire watershed, which extends into parts of Massachusetts, New Hampshire, Vermont, and Rhode Island, increased from 7.8 million to 8.8 million).

Population growth leads to development that adds parking lots, rooftops, streets, and other hard surfaces to the “built” environment. Hundreds of studies around the U.S. suggest that water quality and overall stream health decline when impervious surfaces exceed 10 percent in a watershed (the area of land that drains into a body of water). When the impervious area in a watershed exceeds 25 percent, stream conditions become severely degraded. In many of the local subwatersheds surrounding the western basin of the Sound, developed land exceeds 51 percent, and can be as high as 89 percent. Without vegetation and healthy soils fltering pollutants, stormwater runoff can carry pesticides, pathogens, motor oil, debris, and excess nutrients into storm drains and streams. These pollutants eventually fow into the Sound.

Also of note:

  • Tidal wetlands are a critically important habitat along thshoreline. Until the 1970s, the value of wetlands was not widely recognized.
  • Despite efforts to protect them, some wetlands are losing vegetation and converting to mudflats.
  • Eelgrass is an important underwater plant for fish and other wildlife. Learn more about Long Island’s Seagrass Conservation Web site, and information about the Sound’s different habitats at

To download the full report, plus to view a plethora of links to websites helpful to learning more about protecting Long Island Sound and its watershed visit

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