Scientists at Stony Brook University have released a new report detailing significant water quality issues in Long Island's surface waters for 2024. The study highlights the presence of 36 "dead zones" with critically low oxygen levels, posing threats to marine life.
Throughout the summer months, every major bay and estuary on Long Island experienced harmful algal blooms (HABs), dead zones, or fish kills. Excess nitrogen from wastewater is identified as a primary cause. Chris Gobler, PhD, SUNY Distinguished Professor and Principal Investigator of the research, warns that without intervention, these occurrences may worsen with climate change. “It has become clear that, absent aggressive change, Long Island should expect the wide-spread occurrence of low oxygen zones and HABs during summer and these events could worsen with climate change,” he stated.
The New York State Department of Environmental Conservation stipulates that waters must maintain a minimum of three milligrams of oxygen per liter to support aquatic life. This summer witnessed six fish kill events where oxygen levels dropped below this threshold.
In addition to dead zones, more than two dozen lakes and ponds on Long Island experienced blue-green algal blooms in 2024. These blooms produce toxins harmful to humans and animals and have been linked to illnesses in dogs both locally and nationally. Seventeen water bodies on Long Island's south fork were notably affected.
Marine areas saw over 25 HAB incidents; however, no shellfish beds were closed due to these events in 2024. Notably intense was an August rust tide starting in Shinnecock Bay and spreading through most of the Peconic Estuary. Gobler noted climate change exacerbates such phenomena: "Beyond warmer temperatures intensifying dead zones...climate change is bringing more intense rainfall events that deliver high levels of nitrogen."
A record rainfall event on August 19 delivered over ten inches of rain to parts of Long Island leading to subsequent HABs and shellfish bed closures due to bacterial contamination. Gobler emphasized the need for reducing nitrogen loads: “Since these events deliver excess nitrogen to coastal zones, they are a clarion call to double down on nitrogen load reductions..."
Despite negative trends, there are positive developments such as shrinking dead zones in Long Island Sound following nitrogen reduction efforts.
The deterioration has affected vital marine habitats including seagrass beds and fisheries like bay scallops and hard clams while also compromising coastal wetlands that buffer storm impacts. Excessive nitrogen from household sewage is primarily responsible for these conditions.
Suffolk County and Nassau County completed studies identifying wastewater as the main nitrogen source threatening surface waters. They set targets for reducing septic system-related nitrogen discharges.
This report by the Gobler Laboratory at Stony Brook University results from consistent monitoring since 1999 alongside data from New York State Department of Environmental Conservation and funded by U.S. Environmental Protection Agency's Long Island Sound Study.