The East Hampton Town Trustees will likely extend the closure of Georgica Pond in East Hampton to the harvesting of crabs and fish, as microcystin toxin, a product of the blue-green algal bloom known as cyanobacteria that can cause liver damage in humans and animals, has now been measured in the water body. Georgica is closed to the taking of shellfish other than crabs year round.
At the same time, algal blooms known as cochlodinium, or rust tide, have been detected in isolated sections of Three Mile Harbor, Accabonac Harbor, and waterways around Sag Harbor, a trustee said.
Microcystin, produced during algal blooms such as the cyanobacteria detected in Georgica Pond two weeks ago, is present at low levels, Christopher Gobler of Stony Brook University’s School of Marine and Atmospheric Sciences wrote in an email. Dr. Gobler has been monitoring water quality, in conjunction with the trustees, in waterways the trustees oversee on behalf of the public, since last year. The measurement of heightened levels of cyanobacteria prompted the trustees to hold a special meeting on July 24 at which they passed a resolution prohibiting the taking of crabs and other shellfish and marine life from Georgica Pond.
Cyanobacterial blooms can deplete oxygen in waterways, threatening marine life and drinking and irrigation water supplies. Such blooms can form in waterways during warm weather, particularly when elevated levels of nitrogen or phosphorus are present.
“The levels of blue-green algae in the pond have remained at a moderate level during the past 10 days,” Dr. Gobler wrote. At .5 micrograms per liter, the level of microcystin measured is low, representing one-half the drinking-water standard set by the World Health Organization.
The same algal bloom growing in Lake Erie and detected at a water treatment plant serving Toledo, Ohio, is behind the recent loss of drinking water for half a million people. Georgica Pond is not used for drinking water, Dr. Gobler wrote, “and thus these levels are not a serious threat, even for recreational use.”
However, “winds can create surface scums of algae, concentrating them and potentially creating a ‘high probability threat.’ ” According to the World Health Organization, scums can represent thousandfold concentrations of microcystin. People and pets, Dr. Gobler wrote, “should always avoid dense aggregations of thick, green material on the shoreline.”
“Our board will likely have to extend the resolution to keep Georgica Pond closed to crabbing until these levels of toxins subside,” Stephanie Forsberg, the trustees’ assistant clerk, wrote in an email, “since the chance for these toxins to reside in marine life is possible, but we do not know for certain.” The trustees will discuss the matter when they meet on Tuesday, Dr. Forsberg wrote.
Dr. Forsberg said that rust tide is not toxic to humans but in high densities can be toxic to fish and shellfish. “The good thing about rust tide is that it tends to be patchy and could leave as quickly as it appeared, so we are hoping for the best case scenario and for that to occur,” she wrote of the blooms in Accabonac and Three Mile Harbors, “but unfortunately only time will tell.”