Red tide is again sweeping into some of New England's coastal waters, forcing New Hampshire state officials to ban harvesting of mussels, clams and oysters from that state's coastal waters and Hampton/Seabrook Harbor.
The ban is in response to high levels of Paralytic Shellfish Poisoning, known as red tide, that have been found in blue mussels collected from the Isles of Shoals and the harbor. Closures have not come to the North Shore of Massachusetts, but signs of risk are there, especially if the region were to be hit with a storm, said Dan Whitaker, senior biologist for the Massachusetts Division of Marine Fisheries.
"We've luckily dodged a bullet so far," Whitaker said. "We went out and sampled Thursday, and those samples came back negative."
In late April, scientists at the Woods Hole Oceanographic Institution reported in a Gulf of Maine toxicity study that the number of cysts of red tide algae seat was 30 percent higher than the devastating 2005 red tide bloom and crisis, which brought the shutdown of more than 1 million acres of Massachusetts shellfish beds — most of them in Essex County — from mid-May through mid-July. State Division of Marine Fisheries officials said then they were already monitoring the situation.
New Hampshire Shellfish Manager Chris Nash, of the state Department of Environmental Services, said it's too soon to know how long the newly enacted ban there will last, or how severe it will be. However, toxicity in Hampton/Seabrook is appearing earlier than in previous years, he said.
Officials at the DES made the decision to ban shellfish harvesting to protect public health.
"Red tide toxicity levels are increasing right now, in both offshore and near-shore waters," Nash said. "It is too soon to know how severe this algae bloom will be, or how long it might last."
Blue mussels collected from Hampton/Seabrook two weeks ago showed low toxin levels, but samples collected last week exhibited toxin levels above the mandatory closure threshold of 80 micrograms of toxin per 100 grams of shellfish tissue. Blue mussels from Star Island, Isles of Shoals, are also exhibiting high toxicity values, authorities said.
Some weekend rain and the New Hampshire closures will have Massachusetts officials on alert for North Shore clam flats.
"With the rain directly washing off land and feeding these things, then the wind keeping them on shore with a medium of fresh water and humus (decomposed organic material), it's perfect conditions for growth of these (red tide) cells," Whitaker said.
He added, however, it takes time for the levels to rise in any of the shellfish. While the red tide bloom of 2005 was the most widespread toxic event on record for New Hampshire waters, the past two years have had less-severe events, characterized by high toxicity in the offshore Atlantic waters and lower levels of toxin along the beaches.
Red tide is a condition in which filter-feeding molluscan shellfish, such as clams, oysters and mussels, accumulate a potent neurotoxin produced by a naturally occurring marine algae. Studies have shown that ingesting the toxin is potentially fatal to humans, and cooking does not make contaminated shellfish safe for consumption.
Some Associated Press material is included in this report.
