On The Water: Less Nitrogen Pollution Leads To A Sound Rebound

HUDSON VALLEY, NY — A new study from the Environmental Protection Agency (EPA) finds that water quality in the Long Island Sound has shown significant improvement thanks in part to efforts to reduce nitrogen pollution in the watershed.

The agency reports that almost 50 million pounds of nitrogen pollution is being kept out of the sound waters each year. The improvement is largely credited to successful programs in Connecticut and New York to upgrade wastewater treatment plants to remove nitrogen before treated sewage is discharged into the sound.

“This study is good news for the Long Island Sound and its neighboring communities, as it highlights successful actions taken to improve the Sound’s water quality,” New England EPA Administrator Deborah Szaro said of the encouraging results. “Using science to inform our decisions, while maintaining a strong partnership with the states of Connecticut and New York, helps us continue to protect and restore the Sound, as well as plan for future action.”

The two state-led programs have reduced millions of pounds of nitrogen pollution from being discharged into the Long Island Sound. The reduction in nitrogen has in turn led to increased oxygen concentrations in the sound during the hot summer months. The efforts have resulted in noticeably improved ecological conditions for sea life.

As the weather turns hot, concentrations of dissolved oxygen (DO) in Long Island Sound water declines to levels unhealthy for aquatic life. The low oxygen levels, known as hypoxia, are most pronounced in the bottom waters of the western portion of the sound.

Hypoxia in the sound occurs each year when excess nitrogen in the water causes algae blooms. Bacteria feed on the algae and deplete the water of oxygen. Some species of fish, crabs and lobsters flee the area in the summer, while other species simply perish.

A peer-reviewed study from the University of Connecticut published this year concludes that improved water quality can be directly attributed to upgrades to wastewater treatment plants in states bordering the Long Island Sound watershed.

“Water quality in Long Island Sound is improving thanks in large part to dramatic reductions in nitrogen pollution, which is great news for the Sound’s ecosystem and local communities,” EPA Regional Administrator Walter Mugdan said. “Here in New York, we have seen tremendous success in New York State’s work to keep nitrogen from reaching the Sound in treated sewage, which will have a lasting impact for years to come.”

Since the 1990s, Connecticut and New York have worked in partnership with the EPA to implement a nitrogen pollution reduction plan, known as the Total Maximum Daily Load plan, in an effort to improve the sound’s DO levels. The just released study shows evidence that the decades-long work is paying off.

Through infrastructure investments of more than $2.5 billion to improve wastewater treatment, the total annual nitrogen load to Long Island Sound is now some 47 million pounds less than the yearly discharge in 1990, according to the EPA. The area of hypoxia, based on a five-year rolling average, was 94 square miles in 2020, compared to the yearly average from 1987-2000 (before the plan took effect) of 205 square miles.

Officials say the improvements to water quality in the Long Island Sound is one of the few documented cases in the world of the recovery of a nutrient-caused hypoxic coastal system.