Most of western Shinnecock Bay remains closed to shellfishing due to the presence of a potentially deadly marine biotoxin produced by a “red tide” algae bloom.
The closure, imposed last Thursday, May 7, by the New York State Department of Environmental Conservation, marks the third time in the past four years that the western portion of the bay has been closed to shellfishing in the spring because of the blooms of the algae, known as Alexandrium. The restriction applies to all bi-valve shellfish and gastropods, like conch, whelk and moonsnails.
No human cases of biotoxin illness have ever been reported from ingesting shellfish taken from western Shinnecock Bay and, in years past, the restriction on the harvest of shellfish has typically been lifted by early June, when the algae blooms dissipate as the bay waters warm. Scientists said this week that the Alexandrium bloom is already showing signs of beginning to die out.
The DEC’s decision to close approximately 3,900 acres of bay bottom in Southampton Town came after shellfish collected from monitoring sites in Weesuck Creek in East Quogue showed levels of saxitoxin two times higher than the federal threshold for closing down shellfish harvesting.
Saxitoxin is a marine biotoxin that causes paralytic shellfish poisoning, or PSP. Saxitoxin poisoning has sickened hundreds nationwide over the last decade and even caused two deaths in the Pacific Northwest in 2010 when people ate shellfish tainted with it.
The DEC first closed Shinnecock shellfishing because of Saxitoxin concerns in 2011 and 2012. In those years the DEC protocol was to close all shellfish harvesting if any saxitoxin was detected. In 2013 the DEC changed its protocol and started measuring the amounts of the toxin found in shellfish samples and in 2013 and 2014 did not close shellfishing in the bay because the levels detected were not dense enough to cause health concerns. But this year the levels of the toxin found in samples leapt to more than three-times previously detected levels.
Scientists are not sure why the levels jumped this year.
“Usually we’re getting 40 or 50 micro-grams of saxitoxin…this year it got up to 170 micro-grams,” said Christopher Gobler, Ph.D. a marine bioligist at Stony Brook University School of Marine and Atmospheric Sciences, and a leading expert on aquatic algae blooms. “We don’t know the epicenter of the bloom. We’re finding the cells, we know the shellfish are most toxic in Weesuck Creek and we think the cells are washing in from north of that area but we’re not certain.”
Alexandrium is one of two problematic red algae species that have bloomed in local bays in recent years. The second species, a swimming dinoflagellate called Cochlodinium, typically emerges in late July and, unlike Alexandrium, is typically widespread throughout eastern Shinnecock Bay and the Peconics, and lasts for two to three months.
Cochlodinium poses no health risks for humans and has not led to closures of any fisheries, but it can be deadly to fish and shellfish, and has been blamed for massive die-offs of scallops and isolated fish-kills in enclosed harbors.
Cool weather and light rainfall in the spring and summer of 2014 led to greatly reduced densities of both red algae blooms. There were no shellfish closures from Alexandrium last year and a robust scallop harvest and bountiful fish stocks in the Peconics were attributed to the relative absence of the Cochlodinium blooms that have tiger-striped the bays a rusty red—dubbed “the rust tide” by scientists—in the decade since the blooms first emerged in local waters.
The DEC has also closed approximately 100 acres of underwater land in neighboring Riverhead Town last week as well due to blooms of Alexandrium. The DEC has 13 locations across Long Island that monitor for the presence of biotoxins.
The DEC will continue to monitor the toxicity levels in the shellfish in Southampton Town over the next few weeks. Harvesters are encouraged to call (631) 444-0480 for the latest information on the closures.