Now for More Bad News About the Water

The discovery last month of cochlodinium, or rust tide, in Three Mile Harbor in East Hampton came amid the ongoing closure of Georgica Pond to the harvesting of crabs and other marine life due to the discovery in July of another toxic algal bloom, cyanobacteria.

Rust tide, which is not harmful to humans but can kill shellfish and finfish, has now appeared in town waterways for 11 consecutive years, with recent sampling by Christopher Gobler of Stony Brook University showing some of the highest densities since its first appearance. The algal bloom is a potential threat to this autumn’s bay scallop harvest.

“The rust tide has been blooming in Three Mile Harbor for three to four weeks now,” Dr. Gobler wrote in an email on Monday. “It has also been blooming in Sag Harbor and Accabonac Harbor, although less so recently in the latter,” he wrote.

Diane McNally, clerk of the East Hampton Town Trustees, who manage town waterways on behalf of the public, said that Georgica Pond would remain closed because of the continued presence of cyanobacteria, or blue-green algae, which she said is not widespread. Cyanobacteria produces toxins that can be harmful to people and animals if ingested. The pond’s status was to be on the agenda of the trustees’ Aug. 26 meeting, which was canceled.

In a document related to Georgica Pond dated Sunday, Dr. Gobler wrote that the water-quality monitoring he has been doing in conjunction with the trustees for the past two years has revealed multiple problems, including low oxygen levels, fish kills, blooms of macroalgae, or seaweeds, and cyanobacteria blooms. High levels of nutrients such as nitrogen and phosphorus, as well as high temperatures and poor water circulation, promote the growth of cyanobacteria. “These issues must be addressed to alleviate these blooms,” he wrote.

Development of a management plan to address the pond was the focus of an Aug. 14 meeting between representatives from East Hampton Town and Village, the trustees, the Nature Conservancy, Dr. Gobler, and an environmental consultant. The plan was also a topic at the town board’s work session on Tuesday.

The pond should be opened to the ocean more frequently and for longer periods in order to increase flushing, raise salinity levels, and lower nutrient levels, Dr. Gobler wrote, all of which should discourage the development of algal blooms. However, “there are no comprehensive reports on the response of Georgica Pond to these openings; they could have unintended consequences on the ecosystem and its human and nonhuman residents or may be fully beneficial,” he wrote. “Once they are better understood, openings may be utilized more frequently or strategically to benefit all users of the pond.”

The most prominent nutrient sources must be identified, and the relative importance of nitrogen and phosphorus in promoting cyanobacteria blooms over a full year must be assessed, Dr. Gobler wrote.

A watershed management plan in development by participants of the Aug. 14 meeting will follow Dr. Gobler’s recommendations, East Hampton Town Supervisor Larry Cantwell said at the work session. Kim Shaw, the director of the town’s Natural Resources Department, will work with the trustees and the New York State Department of Environmental Conservation to that end, he said.

Use of fertilizers in watershed areas should be limited, according to the plan, and barriers installed at key locations to prevent pollutants from entering the pond. Natural buffers along the shoreline should be enlarged, and shoreline property owners should be educated as to the detrimental impact of fertilizer on the pond’s health.

The discussion also included requiring maximum setbacks from waterfront areas in all new construction, and the replacement of aging septic systems from which nutrients may be leaking into the watershed.

With reporting by Joanne Pilgrim