The State Department of Environmental Conservation halted shellfish harvesting in Sag Harbor Cove this week after high levels of a neurotoxin produced by “red tide” algae blooms was detected in shellfish there.
It is the second year in a row that the cove has been closed to shellfish because of the presence of the toxin. Other East End embayments that also have had shellfish closures because of the red tide toxins have not yet been closed, and scientists say that the cold temperatures of early spring may have dampened the impact of this year’s first red tide bloom.
“Everything is a little bit delayed this year, because it’s been so cold, but this is the prime season for it,” said Dr. Christopher Gobler, a marine biologist and professor at Stony Brook University who has been tracking algae blooms on Long Island for more than 20 years. “This algae makes cysts, like seeds, that let it come back year after year. Once it has gained a foothold, it’s going to come back year after year—it’s just a matter of how bad it is going to be.”
There is hope that this year’s bloom of the algae, a crimson red species known as Alexandrium, will not be particularly bad.
The algae thrives when water temperatures are between 50 and 65 degrees. Once water temperatures approach 70 degrees, the algae tends to subside. Because of the cold winter and spring, water temperatures took much longer to rise into the 50s than in years past, and a warming trend in the last two weeks has pushed them up quickly.
The water in Sag Harbor Cove this past weekend was 65 degrees. If temperatures continue to rise steadily, it is possible that the Alexandrium could fade away before reaching critical densities in other local water bodies.
Last year, shellfish beds in western Shinnecock Bay and Flanders Bay also were closed because high levels of the toxin, known as saxitoxin, were found in shellfish there. The first closures came in the first week of April, and most shellfish beds had been cleared for harvesting again by late May as the red tide faded.
Dr. Gobler said that his students have been taking samples throughout the East End and have found Alexandrium in the waters of western Shinnecock and Flanders Bay but not in very high concentrations. He said there have been traces of saxitoxin found in some shellfish in those places too, but not at levels high enough for the state to deem them dangerous to be consumed.
Saxitoxin is not harmful to fish or shellfish, which feed on the Alexandrium algae, but it can be deadly for humans if ingested by eating shellfish that have accumulated it in their flesh. The toxin was blamed for two deaths and hundreds of illnesses in the Pacific Northwest in 2010.
Once the Alexandrium has faded out, concerns will switch to the anticipated emergence of another red tide in midsummer. That second species, a dinoflagelate known as Cochlodinium, is not harmful to humans but can kill fish and shellfish when blooms reach a sufficient density. Cochlodinium, which blooms in a darker reddish-brown than Alexandrium, is much more widespread. It appeared in eastern Shinnecock and throughout the Peconics, Shelter Island Sound, and Gardiners Bay in recent years, and it has been blamed by many for a widespread die-off of bay scallops last summer.