Toxic blue green algae have been found in Maratooka Pond in Mattituck
Toxic blue green algae have been found in Marratooka Lake in Mattituck

Blue-green algae blooms have become an endemic problem in Lake Agawam in Southampton and Mill Pond in Water Mill, but have been scarce on the North Fork until last week Marratooka Lake in Mattituck turned an eerie shade of green.

The state DEC is warning that a widespread algae bloom with “high toxins” has been confirmed in the pond as of Sept. 27, and is asking people to avoid contact with the water and not let their pets near the lake.

Though most blue-green algae is harmless, the DEC said Marratooka Lake, a 24-acre lake that sits between Mattituck High School on the Main Road and New Suffolk Avenue, has tested positive for microcystin, a specific protein sometimes created by blue-green algae that is known to cause damage to plants and animals.

The Suffolk County Health Department's sign at Maratooka Lake.
The Suffolk County Health Department’s sign at Marratooka Lake.

A sign posted by the health department on the New Suffolk Avenue side of the pond urges people to not swim, wade or fish near algae blooms and to not drink the water or allow animals or children near it. The sign urges people to seek medical attention and contact the health department if they have symptoms of nausea, vomiting, diarrhea, skin eye or throat irritation, allergic reactions or difficulty breathing after coming in contact with the water. Microcystin is a known liver toxin.

The signs didn’t scare away two young fishermen who had just put in an aluminum jon boat in the murky waters early Tuesday morning. They’d read the signs, they said, and the pond was greener than they’d ever seen, but they were going fishing anyway.

Blue-green algae blooms are believed to be caused by a combination of high levels of phosphorus and nitrogen (fertilizer ingredients), sunlight, warm weather and stagnant water, according to the DEC. At high concentrations, algae can also deprive ponds of oxygen, causing widespread fish deaths, as has happened in the past in South Fork ponds with high algae levels. Both Lake Agawam and Mill Pond have been on the DEC’s blue-green algae bloom list since early this summer, with “widespread” algae blooms. Lake Agawam, Mill Pond and Marratooka now make up three of the six freshwater bodies in the state with widespread blue-green algae blooms.

Marratooka Lake is not the only freshwater lake on the East End that is having problems this fall. On Sept. 27, Shelter Island banned swimming at Fresh Pond, a 15-acre pond on the west side of the island just inland from West Neck Creek, due to high levels of phosphorus and coliform bacteria.

“In addition to elevated phosphorus levels….September coliforms are high as well — perhaps for seasonal reasons,” wrote Shelter Island Town Supervisor James Dougherty in a letter to residents Sept. 27. “Since the swimming season is effectively over anyway, the town is going to officially close the pond for swimming and continue our testing.”

Blue-green algae in Marratooka Lake
Blue-green algae in Marratooka Lake

Beth Young
Beth Young is an award-winning local journalist who has been covering the East End since the 1990s. She began her career at the Sag Harbor Express and, after receiving her Masters from the Columbia University Graduate School of Journalism, has reported for the Southampton Press, the East Hampton Press and the Times/Review Media Group. She founded the East End Beacon website in 2013, and a print edition in 2017. Beth was born and raised on the North Fork. In her spare time, she tinkers with bicycles, tries not to drown in the Peconic Bay and hopes to grow the perfect tomato. You can send her a message at

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