dead diamondback terrapin
Turtles began washing up along the shores of Flanders Bay in April | courtesy Karen Testa

A typical Alexandrium bloom on Long Island lasts about three to four weeks in May, though they can begin as early as April and last into June. The hypoxic conditions are evidence of the decay phase of the bloom, during which there are fewer and fewer toxic algae cells in the water. The dead turtles appear to have stopped washing on shore as well, another signal that, if they were poisoned by saxitoxin, the bloom may be near the end.

“We haven’t gotten a call in the past four or five days. That’s a good sign,” said Ms. Testa on Tuesday.

While the bloom may be winding down, the solution to preventing future toxic food web implosions isn’t an easy one, and there’s no clear answer to why some creeks and bays have toxic algae in them and others don’t. This is often compounded by other water quality issues that have closed creeks to shellfishing.

dead bunker
In past years, such as in this 2008 picture at the end of Long Neck Boulevard in Flanders, bluefish had driven bunker onto the shores of Flanders. But something more is happening this year.

For example, in the Flanders Bay area, only the three creeks already closed by the DEC were found by the Suffolk County Health Department to have high concentrations of Alexandrium, despite media reports over the weekend that said Flanders Bay was closed due to saxitoxin contamination, said Ms. Severino.

The Suffolk County Health Department reported on Saturday that water samples collected last Friday, May 15, “throughout Flanders Bay and its tributaries by the Suffolk County Department of Health Services (analyzed under contract to SCDHS by Stony Brook University),” found “that elevated concentrations of Alexandrium (the harmful algae that causes PSP) appear to be contained to Terry Creek/Meetinghouse Creek and James Creek.”

Grace Kelly-McGovern of the health department pointed out that all of the tributaries and the western portion of Flanders Bay are already closed to shellfishing due to bacteriological concerns, not due to saxitoxin.

The solid waste leaching from cesspools in the neighborhoods surrounding Flanders Bay are already a suspected factor in the bacteriological contamination, and the nitrogen from liquid waste in those cesspools compounds that injury by providing nutrients for algae blooms. Riverhead’s sewage treatment plant at the mouth of the Peconic River has also been cited for dumping waste with too much fecal coliform bacteria in it into the river three times in November of last year.

But testing for fecal coliform levels is an entirely different practice than testing for toxic algae.

Southold Town Trustee John Bredemeyer, a biologist who serves as the head of Southold’s shellfish advisory committee, is concerned that the publicity surrounding toxic algae will distract the DEC from its work testing shellfish for bacteriological contamination, which is also harmful to humans.

“When the DEC has to respond to potential public health threats, they don’t get their bacteriological work done,” he told the Southold Town Board at their work session Tuesday.

Mr. Bredemeyer added that Alexandrium blooms were historically found in open waters off the coast of New Hampshire and Maine, in areas where there was little input from man-made pollution sources. In those areas, Alexandrium blooms tend to occur after a spring that saw a great deal of snow melt, similar to what we’ve seen on Long Island this winter.

“They keyed in on areas with lower salinity that were known to have a high influx of groundwater,” he said. “Iron and certain other metals in the groundwater served as chelating or sequestering agents, a complex mix that pushed these blooms to grow.”

But the public opinion consensus here seems to be swaying toward the nitrogen explanation.

One thing is clear: eating bivalves with saxitoxin was unlikely to have been good for the turtles,” said the Long Island Coastal Conservation Research Alliance on their Facebook page this week. “A bad week got worse for the western Flanders Bay region over the weekend when 1,000s of bunker died, likely from low oxygen associated with dense algal blooms. This same region has experienced a toxic algal bloom, a paralytic shellfish poisoning closure of shellfish beds, and an unprecedented die-off of hundreds of diamondback terrapin turtles in the past 10 days. This highlights the negative consequences of excessive nitrogen loading into a shallow water body that is poorly flushed.”

Ms. Testa agreed.

“How water gets polluted is nitrogen from cesspools and fertilizers,” she said. “It’s a waste byproduct of us and farming.”

The DEC expects to have the results of the tissue sampling in two to three weeks, said Ms. Severino.

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Beth Young
Beth Young is an award-winning local journalist who has been covering the East End since the 1990s. She began her career at the Sag Harbor Express and, after receiving her Masters from the Columbia University Graduate School of Journalism, has reported for the Southampton Press, the East Hampton Press and the Times/Review Media Group. She founded the East End Beacon website in 2013, and a print edition in 2017. Beth was born and raised on the North Fork. In her spare time, she tinkers with bicycles, tries not to drown in the Peconic Bay and hopes to grow the perfect tomato. You can send her a message at

4 thoughts on “The Strange Case of the Dead Turtles of Flanders Bay

  1. have conditions gotten better in flanders bay,,,, is it ok to swim there now??

  2. This morning we found a very large die-off (up to 1,000) of fish on the shore of Red Cedar Point/Flanders Bay. Eastern shore of Flanders Bay and Western shore of Great Peconic Bay.

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