Blue-Green Algae Bloom Strikes Georgica Again

The East Hampton Town Trustees have closed Georgica Pond in East Hampton and Wainscott Pond to the harvesting of shellfish, crabs, and other marine species until further notice after detection of cyanobacteria, or blue-green algae, blooms in both ponds.

The Suffolk County Department of Health alerted the public to these blooms and five others in the county, including in Mill Pond in Water Mill and Lake Agawam in Southampton, on Friday. Exposure to cyanobacteria at high concentrations can cause vomiting, diarrhea, skin, eye, or throat irritation, nausea, allergic reactions, or breathing difficulties.

Blue-green algae levels in Georgica Pond were undetectable through mid-June, but they began to exceed the New York State Department of Environmental Conservation's threshold for a bloom in the southern part of the pond, according to Christopher Gobler of Stony Brook University's School of Marine and Atmospheric Sciences, who monitors water bodies under trustee jurisdiction. Levels in Georgica Cove and at the north of the pond are elevated, he told the trustees on Friday, but below the D.E.C.'s threshold. Testing for the blue-green algal toxin microcystin was to occur on Friday and Saturday.

Georgica Pond has been plagued by cyanobacteria blooms over the past several summers, when warmer water temperatures and a lack of tidal flushing have promoted the blooms. Excessive nutrients including nitrogen and phosphorous are also blamed. The biannual opening of the pond to the Atlantic Ocean, typically done in the spring and fall, restores salinity levels and the blooms quickly dissipate.

This is the third consecutive year that the trustees have closed the pond, though the previous closures began in late July 2014 and early August 2015. The earlier bloom this year, according to Dr. Gobler, is almost certainly due to the fact that the pond has been closed to the ocean since early spring. He told the the trustees that it has filled it with "nutrient-enriched freshwater and driven the salinity down to levels permissible for blue-green algae."

Dr. Gobler, who is also providing data to the Friends of Georgica Pond Foundation, a group of property owners working toward restoring its ecological health, added in his message to the trustees that levels of blue-green algae are likely to increase in the coming weeks due to warm temperatures and the pond's continued closure to the ocean.

Blue-green algae, naturally present in many lakes and streams, is harmless at low levels. Excessive algal growth, however, discolors water and produces floating rafts or scum on the surface. Large blooms can dramatically reduce dissolved oxygen, killing fish and other living organisms.

The Health Department has advised the public not to swim or wade in the affected waterways and to keep pets and children away from the area. Clean water should be used immediately to rinse exposed areas if contact does occur, and medical attention sought if any of the aforementioned symptoms are observed.