In 2022, signs along Sagg Pond in Sagaponack warned of...

In 2022, signs along Sagg Pond in Sagaponack warned of high levels of blue-green algae blooms in the pond. This year, similar blooms were found elsewhere, including in Marratooka Lake in Mattituck. Credit: John Roca

Suffolk County health officials are advising residents to avoid a North Fork lake contaminated with a toxic algae known as cyanobacteria.

Stony Brook University biologists confirmed the presence of the blue-green algae in Marratooka Lake in Mattituck, according to officials. Residents are urged to avoid recreation activities in the lake’s waters and keep their children and pets away from the area.

While blue-green algae is naturally present in lakes and streams in low numbers, it can become abundant, forming green, blue-green, yellow, brown or red blooms. It can also produce floating pond scum on the water’s surface, or induce a paint-like appearance in the water.

In a news release, Suffolk health officials advised Long Islanders to avoid contact with any waters that appear “scummy or discolored.” If such contact occurs, officials recommend rinsing off with clean water immediately. They also advise anyone exposed to cyanobacteria to seek medical attention if they experience skin, eye or throat irritation, allergic reactions, difficulty breathing, nausea, vomiting or diarrhea.

Cyanobacteria advisories are commonplace for Marratooka Lake, Southold Town Supervisor Al Krupski said in a telephone interview.

Health officials did not confirm the cause of the cyanobacteria bloom.

In recent weeks, Suffolk County health officials said Stony Brook biologists confirmed the presence of cyanobacteria blooms in Wainscott Pond in Wainscott, Roth Pond in Stony Brook, Wolf Pit Lake in Mattituck, Long Pond in Sag Harbor, Poxabogue Pond in Sagaponack, Mill Pond in Water Mill and Agawam Lake in Southampton.

To report a suspected blue-green algae bloom at Suffolk County beaches open to swimming, residents can contact the Suffolk County Department of Health Services’ Office of Ecology at 631-852-5760 or email

Algae blooms found at bodies of water not open to bathing can be reported to the state DEC at


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