The landmark study, authored in collaboration with University of Connecticut Professor Jamie Vaudrey, examines the health of New York City-area waterways—the East River and Long Island Sound—where $1 billion has been invested to tackle nitrogen pollution. Excess nitrogen (often from treated sewage) depletes oxygen in the water and causes “dead zones” that lead to fish die-offs. High nitrogen levels also fuel toxic and nuisance algae blooms and deterioration of coastal marshes that protect shoreline communities from storm surges.