High levels of Cochlodinium detected in Sag Harbor cove last week could put shellfish and finfish at risk.
By Mara Certic
Just weeks after blue-green algal blooms were detected in Georgica Pond, extremely high levels of the toxic rust alga Cochlodinium have emerged in Sag Harbor and East Hampton waters.
Cochlodinium first appeared on Long Island in 2004 and has been detected in local waters every summer since. According to Professor Christopher Gobler, who conducts water quality testing and is a professor at Stony Brook University’s School of Marine and Atmospheric Sciences, densities above 500 cells per milliliter can be lethal to both finfish and shellfish. The Gobler Laboratory recorded Cochlodinium at densities exceeding 30,000 cells per milliliter in Sag Harbor Cove, and over 1,000 in Accabonac and Three Mile Harbors.
The eastern location and timing of this year’s bloom surprised scientists, because for the past 11 years, the water quality experts have tracked west-to-east algal migration. “With blooms typically emerging in the tributaries of the far-western Peconic Estuary in mid-to-late August,” Professor Gobler said.
“Our Long Island Water Quality Index program samples all of Long Island from Queens to Montauk on a weekly basis and has found the western Peconics to be clear of rust tide. Late last week, we saw rust tide at moderate levels in East Hampton and thought it might be a blip,” he said.
“However, this week, the rust tide spread to at least three distinct harbors and reached a level in Sag Harbor we have not seen anywhere on Long Island in several years.”
According to a laboratory technician who helps conduct the water quality testing for the Trustees, Cochlodinium was detected in small amounts in Accabonac Harbor two weeks ago. The algae were not visible at that time, he said, but made it more difficult to see the sea floor.
The following week, the rust tide was detected in similar levels in Three Mile Harbor and at levels so high in Sag Harbor Cove that the algae bloom was noticeable on the surface of the water in some areas.
Professor Gobler might have an explanation as to why these blooms appeared in Eastern waters this year. “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,” he said in the release.
Professor Gobler addressed the Southampton Town Board during a work session on Thursday, August 7, during which he proposed two projects, which would provide the scientific data local lawmakers need to mitigate nitrogen loading.
The first of these proposals would be a series of questions online which would allow residents to figure out their nitrogen contribution to the watershed. “This can certainly be tailored, improved upon and altered,” Professor Gobler said, adding that it could even be on the new Southampton Town website.
Professor Gobler said that outdated septic systems are responsible for the majority of the nitrogen loading on the East End. Southampton Town has been looking towards developing water quality technology and improving septic systems.
“What level of nitrogen reduction, on a bigger picture, does that require? And that’s a question that no one can answer these days,” Supervisor Throne-Holst said at the work session. The second proposal would attempt to determine by how much nitrogen levels would need to be reduced.
“We’re all dedicated to trying to figure out any way possible not to kill the health of the bay,” Sag Harbor Village Trustee Robby Stein said in a phone interview on Wednesday. “We’re trying to do what we can,” he said, adding that the Village is trying to encourage better policy around nitrogen loading, and has recently created a septic rebate system, which would provide rebates for the replacement of septic systems installed before 1981.
Professor Gobler’s lab has also begun to understand why these algae blooms have occurred every year since they were first detected. “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,” he said. “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.”
During the rust tides of the past few years, scallop populations decreased dramatically in the Peconic Estuary. This year’s high Cochlodinium densities in Sag Harbor have not been seen for a few years, Professor Gobler said.
“While this is somewhat uncharted territory, we anticipate the rust tide will spread and emerge in the western Peconics and Shinnecock Bay in the coming weeks,” he said.
Professor Gobler said that blooms typically continue until water temperatures drop below 60 degrees.
Larger finfish typically can outswim the algal blooms, and are not always affected by the toxic tides. Fish stuck in pound traps, however, can be killed in a matter of hours when the tides roll in.
And although scallops are better swimmers than other bivalves, it is unlikely that they would be able to swim away from a lethal tide. “They’re at the mercy of the environment,” said John “Barley” Dunne, director of the East Hampton Shellfish Hatchery. “They can’t escape an algae bloom,” he said.