How do sewage treatment plants threaten estuaries?
——Jean T. Castagno, Old Saybrook, CT
Estuaries are partially enclosed bodies of water where freshwater and saltwater mix. They are key coastal habitats for many a species of mammal, fish and bird—and are used as spawning grounds for much of our nation’s commercial fish and shellfish. The wetlands associated with estuaries buffer uplands from flooding. Estuaries also provide many recreational opportunities, such as swimming, boating and bird watching. Chesapeake Bay, San Francisco Bay, Boston Harbor, Tampa Bay and Puget Sound are all examples of U.S. estuaries, but one that is particularly plagued by sewer plant drainage is the Northeast’s Long Island Sound.
Norwalk, Connecticut-based Save the Sound reports that 10 percent of the U.S. population lives within 50 miles of Long Island Sound. That’s a lot of people and a lot of sewage. According to the Natural Resources Defense Council (NRDC), “Sewage treatment plants discharge more than one billion gallons of treated effluent into the Sound each day.”
Sewage plants wreak havoc because their daily deposits contain nitrogen, which over-fertilizes the water and causes explosive growth in marine plants. These plants eventually die, sink and decompose. The unnatural amount of decaying material depletes dissolved oxygen levels, creating a condition called “hypoxia,” which Save the Sound says has diminished fish populations, reduced lobster growth rates and negatively affected slow-moving species such as starfish and bay anchovy in Long Island Sound.
Connecticut and New York have both committed millions to improve the health of the Sound with habitat restoration and upgraded sewage plants. There has already been a 19 percent reduction in nitrogen discharges since 1990. A number of state and federal organizations have also banded together to host National Estuaries Day, meant to promote the importance of estuaries and the need to protect them.