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Stony Brook scientist: Algae blooms, dead zones are ‘new normal’ in East End waters

Conditions causing low oxygen and harmful algae blooms in Long Island waters — including on the East End — have become a “new normal,” according to this year’s water quality report from Stony Brook University scientist Christopher Gobler.

From June through October, he reported, every major bay and estuary on Long Island suffered from toxic algae blooms and dead zones in a “dual assault of climate change and excessive nitrogen loading.”

“It began with mahogany and brown tides in June and ended with a harmful rust tide that continues today across eastern Long Island,” Mr. Gobler said in a press release. “In between, a record-setting two dozen low-oxygen dead zones were identified from Great Neck to East Hampton, over 20 lakes and ponds were affiliated with toxic blue-green algae blooms, and fish kills across another half-dozen sites.”

The past summer had nearly double the average rainfall, with more water coming down during individual storms — leading to more nitrogen loading into the sea, feeding harmful algal blooms and dead zones, Mr. Gobler said. He pointed to the expansion and intensification of a mild rust tide on the East End following tropical storms Henri and Ida as an example. 

“It’s one of the longest lasting events, very widespread all across the Peconic Estuary and also in Shinnecock Bay,” he told Times Review. The ongoing rust tide, a harmful algae bloom, began in August.

Mr. Gobler speaking at last week’s press conference. (Courtesy Photo)

The report indicates that Merritts Pond in Riverhead, Hallocks Pond in Jamesport, Marratooka Lake in Mattituck and Great Pond in Southold, among others, suffered toxic blue-green algae blooms this summer. Health officials warn against contact with the algae, which can be harmful to people and animals. Exposure to toxins from the algae can potentially cause symptoms ranging from breathing issues to vomiting or diarrhea.

Mahogany tide was also seen in multiple East End water bodies, including Shinnecock Bay and parts of the Peconic Estuary. Mahogany tide, an algae bloom caused by high nitrogen pollution, sucks up oxygen in the water and is harmful to fish and shellfish. It is not dangerous to people. 

There were also multiple instances of low oxygen, which is harmful to marine life, Mr. Gobler said. 

“These things are initiated by high levels of nitrogen and also by warm temperatures,” he explained. He pointed out that temperatures have increased since the 20th century, especially during the summer, leading to rising water temperatures over the last 20 years. 

“And we know there are really high levels of nitrogen and groundwater that’s entering surface waters in many of these locations, and so without action these things will continue,” Mr. Gobler added. “If we think about climate change, they may even be exacerbated over time. We would expect them to intensify because of that.” 

Courtesy Graphic

He pointed to the local bay scallop population as an example. Scallops have been in a decline this fall, potentially marking the third year in a row East End fisheries have seen a die-off. Failed harvests in 2019 and 2020 led the U.S. Department of Commerce to declare a fishery resource disaster in the state.

“People had been making a living as bay scallop fishermen. That stopped in 2019 when that fishery crashed, and this year will be just as bad as the last two years, if not worse,” Mr. Gobler said. “The scallop, in order to survive, needs clean water, so it needs higher levels of oxygen.”

Scallops can also be harmed if water temperatures rise too much, and rust tides are toxic to the shellfish, he added.

Mr. Gobler said upgrading North Fork septic systems and minimizing fertilizer runoff from local farms and lawns are important to improving water conditions.