An algae bloom that began in the western Peconic Bays in mid-August has spread east, and now covers waters as far from its origins in Flanders Bay and MeetingHouse Creek as Accabonac Harbor in Springs and Gardiners Bay, east of Shelter Island, according to researchers at Stony Brook’s Southampton Coastal and Estuarine Research Program.
The rust tide algae, a dinoflagellate called Cochlodinium, can be toxic to finfish and shellfish at densities above 500 cells per milliliter, while the East End’s other most problematic algae, brown tide, isn’t harmful to marine life until it reaches concentrations of 50,000 cells per milliliter. Rust tide is a different organism from red tide, which is toxic to humans who ingest shellfish contaminated by the algae. Rust tide is, however, believed by some scientists to have been responsible for a die-off of scallops and other marine life last fall.
Rust tide is also different in appearance from other algae blooms. It often appears in bands of dark red water, in contrast to the bluer water surrounding it.
The researchers said Wednesday that, in addition to in the open bays, they have found rust tide in East Creek in Jamesport, North Sea Harbor, Fish Cove in Noyac, Sag Harbor Cove, Coecles Harbor on Shelter Island, and Three Mile Harbor and Northwest Creek in East Hampton, and believe it may be present in other untested waters.
Rust tide has appeared on a smaller scale in East End waters for about a decade. SCERP researcher Chris Gobler has been studying the way cysts formed by the rust tide algae allow the blooms to recur year after year.
“In the last year, we have published two important, new discoveries that help explain the chronic recurrence of these events,” he said in a recent press release. “First, we have discovered the organism makes cysts or seeds which wait at the bottom of the bay and emerge each summer to start a new bloom. At the end of the bloom, they turn back into cysts and settle back to the bay bottom. This allows for the blooms to return every year. Second, we have found that nitrogen loading makes these blooms more intense and more toxic. As nitrogen loading has increased into our bays, these events have intensified.”
Rust tide begins to dissipate in the fall when the water temperature falls below 60 degrees.