There were record numbers of fish kills, dead zones and toxic tides, intensified by summer heat, in Long Island’s estuaries in 2022, according to this year’s assessment of water quality by the Gobler Lab at Stony Brook University.
From June through September, “every major bay and estuary across Long Island was afflicted by fish kills, algal blooms and oxygen-starved, dead zones,” according to the report. “Excessive delivery of nitrogen from onsite wastewater has been cited as the root cause of these disturbing events.”
Dr. Christopher Gobler, Chair of Coastal Ecology and Conservation in Stony Brook’s School of Marine and Atmospheric Sciences, made the announcement at a press conference Oct. 14 on the waterfront in Cold Spring Harbor.
“While some aspects of 2022 were the ‘new normal’, other aspects were a surprise” he said. “Most obviously, there was a ten-fold increase in the number of fish kills during summer 2022, all occurring during the hottest heat of summer, when oxygen levels were dropping to zero in many water bodies at night. The oxygen content of water naturally decreases as waters warm. The excess oxygen demand from decaying algal blooms transform these water bodies into ‘dead zones’ with ‘nocturnal anoxia’, or no oxygen at night.”
The Gobler Lab prepares a map of impaired water bodies each year, which includes lakes and ponds. In 2022, according to the map, more than 20 Long Islands lakes and ponds had toxic blue-green algal bloom, and more than two dozen had low oxygen ‘dead zones.’
The map also showed harmful algal blooms (HABs) in marine waters across the north shore, south shore, and the East End, including a spreading and intensifying bloom of a fish-killing algae in the genus Gymnodinium. This year, for the first time, this algae was in bloom across the Great South Bay and Moriches Bay throughout July and August. This species was already notoriously the cause of the death of more than 500,000 fish in the western Peconic Estuary in 2015.
According to the Gobler Lab, “excessive nitrogen coming from household sewage that seeps into groundwater and ultimately, into bays, harbors, and estuaries or, in some cases, is directly discharged into surface waters, is a root cause of these maladies.”
Both Suffolk and Nassau counties’ subwatershed studies, completed last year, identified wastewater as the largest source of the nitrogen found in surface waters, which is a byproduct of human urine in septic systems. Nitrogen acts as a fertilizer that promotes algae blooms, and when algae blooms die off, the decomposition process uses up oxygen in water that is needed by animals that live there.
This chain of events sets off a domino effect, causing the collapse of seagrass ecosystems and the commercial scallop and clam fisheries that depend on those ecosystems. It also damages coastal wetlands, which are, more and more, a much-needed defense against coastal storms.
Dr. Gobler reiterated his lab’s long-held stance that upgrading septic systems is the best defense against degraded water quality.
“In Long Island Sound, the dead zone in 2022 was nearly 100 square miles smaller than it was 20 year ago, thanks to sewage treatment plants removing 60 percent more nitrogen and reducing the flow of nitrogen into the Sound proper”, said Dr. Gobler. “This proves that reductions in nitrogen loading does improve water quality. It is likely that the fish kills in 2022 would have been far worse had these improvements not been made.”