The extreme western portion of Long Island Sound is suffering from high nitrogen levels, low oxygen and cloudy water but the 1 million-acre system grows healthier in eastern portions where tidal flushing is more prominent.
Rising sea temperatures are also affecting fish populations, with more warm-water species showing up in surveys and numbers of cold-water ones decreasing, according to an ecosystem health report card released Monday evaluating the Sound.
"There's a lot to celebrate about the progress of Long Island Sound but there is a lot to accomplish," said Amanda Bassow, director of the northeast regional office of National Fish and Wildlife Foundation.
Researchers from the University of Maryland's Center for Environmental Science created a water-quality index by measuring nitrogen, phosphorus, chlorophyll, dissolved oxygen and clarity. Excess levels of the nutrients phosphorus and nitrogen can trigger algal growth, depleting oxygen levels.
Researchers also looked at other measurements, such as piping plover populations, eelgrass and bacteria counts.
"The big story we've got from these report cards is one of pollution and dilution coming from either end of the sound," said Bill Dennison, a scientist from the Maryland school. "Long Island Sound goes from highly urbanized, highly impacted to amazingly clean and well-flushed in the East End."
Water from the East River at Manhattan east to Hempstead Bay scored an F grade while its immediate eastern neighbor all the way to Northport earned a D plus. The Smithtown Bay section earned a B minus while areas east to Orient Point earned B and A scores.
"It will be challenging to protect and restore Long Island Sound in the face of population pressure and climate change, but it is heartening that there are still regions in the Sound with good water quality, thriving eelgrass meadows and abundant fish and shellfish," Dennison said.
U.S. Rep. Steve Israel (D-Huntington) said he plans to file a bill by June 30 with Rep. Lee Zeldin (R-Shirley) that would annually provide $40 million in restoration funds and another $25 million for stewardship programs for the Sound. A previous bill expired in 2011. The duration of the funding has not been finalized.
"It is not just a body of water," Israel said. "It is our history. It is our legacy. It is our economy and it is our future."
Inner Hempstead Harbor, including Glen Cove Creek and the Middle and Lower harbors, scored an overall grade of D plus but represents a bit of a comeback. In 1987, marine trawls caught no fish and bottom-dwellers like crabs had 80 percent mortality rates because of low oxygen levels.
"Turning the tide on our water quality does not happen overnight," North Hempstead Town Supervisor Judi Bosworth said. "We'll restore Hempstead Harbor."