Mysterious toxic algae that shut down RI shellfishing last fall is back

[USA] For the first time ever last fall, toxin-producing Pseudo-nitzschia algae bloomed in Rhode Island waters and other parts of New England. The reappearance of the neurotoxin that can cause memory loss and brain damage is worrying scientists.

The first water sample containing an unusually high number of an algae that can produce a potent neurotoxin was taken off Newport Harbor last fall.

Within nine days the algae bloom had spread across Rhode Island waters, forcing the state to shut down many of its precious shellfishing beds out of fear that the toxin, once emitted, could be passed up the food chain from oysters and clams to humans. It has happened before in other places.

With as little warning as when it appeared, the algae colony collapsed, leaving no one sickened but raising questions in its wake.

Four months later, the cause is still a mystery that is stumping scientists and vexing state regulators who worry that it may be more than an anomaly.

Shellfishing has always occupied an outsize place in Rhode Island’s cultural fabric, but its importance goes beyond the quahog’s role as a symbol of the Ocean State.

The industry is an economic driver. The “pond-to-plate” movement has spawned new oyster bars around the state, and Rhode Island-grown varieties of the nubby bivalve — East Beach Blondes, Charlestown Salts and Ninigret Cups — are being shipped to restaurants in New York, Washington and Chicago.

Between a recent boost in wild quahog harvests and the revival of oyster farming over the last two decades, the shellfishing industry has seen sales climb to $12 million a year and its employment reach nearly 700 full- and part-time workers.

The state of the industry, however, is largely dependent on the health of the marine environment. The bloom in October was the first time in more than 40 years that shellfishing in Rhode Island had been closed down because of harmful algae.

But it followed close on the heels of a series of so-called rust tides in local waters, caused by a different type of algae. It also appears connected to blooms that erupted in Maine and Massachusetts. And in another ominous sign, a similar bloom returned to Rhode Island waters just a few days ago.

It may be part of a larger trend of harmful algae blooming around the world.

“Rhode Island has been very lucky for decades,” says Sandra Shumway, research professor of marine sciences at the University of Connecticut. “Now it’s no longer immune.”

Until last fall, in the 30 years that Angelo Liberti had worked at the Rhode Island Department of Environmental Management — the last 18 as chief of surface water protection — he had never seen a bloom of a type of algae called Pseudo-nitzschia.

The microscopic algae has always been present in Rhode Island waters, at least as far back as the 1950s, but generally at low levels. Even in high concentrations, the yellowish-brown algae largely blends into the water column.

So there was no visible indication of anything out of the ordinary before the first high cell count was discovered Sept. 26 during routine monitoring by the DEM, explains Liberti, whose job is to monitor water quality in Narragansett Bay and other state waters.

Tests by the Department of Health on the sample pulled off Newport found about 29,000 algae cells per liter, nearly twice the threshold of what’s considered normal. It caught the agencies’ attention, but it didn’t raise alarms.

That changed on Oct. 6 when water samples taken from mid-Narragansett Bay showed much higher levels, including one sample from near Prudence Island that showed 1.2 million cells per liter. More concerning, another sample tested positive for domoic acid, the toxin sometimes produced by Pseudo-nitzschia that can build up in filter-feeding shellfish. It is dangerous to humans and other higher mammals.

Liberti and other Rhode Island officials knew about a particularly aggressive bloom in Maine a week earlier that, in an unprecedented event for New England, had forced a recall of five tons of mussels and clams after samples showed unsafe levels of domoic acid.

So on Oct. 7, before any Rhode Island shellfish tested positive, the state banned all shellfishing in Narragansett Bay, Mount Hope Bay and the Sakonnet River and ordered all dealers to hold on to their catch.

It was the first time that Pseudo-nitzschia had bloomed in Rhode Island waters, and only the second time in recent memory — after a red tide in the early 1970s — that dangerous levels of any type of algae had brought the state’s shellfishing to a halt.

“This was not a bloom that people had a lot of experience with on the East Coast, so we didn’t want to take any chances,” says Liberti.

His team increased the frequency of testing to twice a week and the number of sampling locations from two to 24.

Workers at the Department of Health lab in Providence worked overtime to get results, one DEM staffer was even doing cell counts on his home microscope, and everyone was talking or emailing late each night to figure out if and when to reopen the shellfish beds.

“It was sheer determination,” Liberti says. “I don’t think we could have kept up that pace too much longer.”

Over a week of testing, no shellfish samples showed the presence of domoic acid, and the broad shellfishing ban was lifted.

But on Oct. 20, when littleneck clams taken from Sakonnet Harbor tested positive for the toxin, shellfishing was halted in the lower Sakonnet River. The next day, mussels taken from waters near Wetherill in Jamestown also came up positive, so a ban went into effect for lower Narragansett Bay.

Those bans were lifted a few days later after additional samples came back negative for the toxin.

Over the course of the bloom, domoic acid was found in only 6 of 150 algae samples. Further tests on the two shellfish samples that tested positive determined that the toxin levels were well below what’s considered dangerous by the U.S. Food and Drug Administration.

Although no humans were poisoned, two seabirds that died suddenly did test positive for the toxin. The birds — a cormorant and a seagull — were found on the Warwick shoreline by a resident who also reported seeing other cormorants that appeared disoriented. The DEM collected the dead birds and sent them to a U.S. Geological Survey animal lab in Wisconsin, which determined that domoic acid levels in their bodies were low, but could not conclude that the toxin caused their deaths.

Officials have been frustrated by a lack of definitive answers about the bloom. Why did the algae proliferate at all? Why were concentrations higher in the lower Bay and the ocean? What triggered the production of the toxin?

“Every time you turn around, there’s another question, not another answer,” Liberti says.

The Rhode Island bloom not only came shortly after the one in the Gulf of Maine but it also coincided with another that stretched from Nantucket Sound into Buzzards Bay. Ocean currents off New England tend to move south around Cape Cod and may have carried algae cells with them.

Lending credence to that theory, the first positive tests in Rhode Island were in the state’s ocean waters. The bloom also spread from east to west.

But Liberti says that local factors may have also been involved. Although nutrients in Rhode Island waters have diminished as stormwater regulations have been tightened and sewage treatment plants have improved, they may still have helped fuel the bloom.

After a dry summer that starved the algae of nitrates, phosphates and other nutrients in runoff, rains in late September washed a feast into the water that the Pseudo-nitzschia may have gorged on. But it’s not clear why it thrived and not other types of algae, Liberti says.

As for when and why Pseudo-nitzschia spawns domoic acid, the toxin may help it outcompete other algae, or it may aid in cell growth. Experiments have found that changes in trace metal concentrations in the water can trigger its production. There seems to be little correlation between Pseudo-nitzschia cell counts and toxin production. Often, the poison is emitted after the cell count has started to drop.

Scientists expect algae blooms to become more common as warming oceans and acidifying waters throw off the ecological equilibrium. But UConn’s Shumway says it’s simplistic to blame only climate change. Rather, she says that the exact combination of natural and human-influenced circumstances is unknown.

Ted Smayda, professor of oceanography at the University of Rhode Island, agrees.

“Multiple factors are coming together and leading to its growth,” he says. “But why it should behave that way is quite mysterious.

An extensive bloom in the Pacific in 2015 — which hammered crab fisheries with $100 million in losses — is attributed to an area of unusually warm water that helped fuel the growth of Pseudo-nitzschia. A recent study found a correlation between warm-water ocean phases in the Pacific with previous blooms. But Vera Trainer, a Seattle-based oceanographer with the National Oceanic and Atmospheric Administration, cautions against drawing conclusions about the New England blooms from what’s been found on the West Coast.

“We do know a lot, but there’s a lot we don’t know,” Trainer says.

Which is why scientists say that until the causes of blooms are better understood, it is critical to track algae levels and respond swiftly to abnormalities.

Before last fall, Rhode Island had never been faced with a Pseudo-nitzschia bloom, but protocols were in place to get the word out fast and step up testing. There were minor hiccups, such as when the state ran out of testing kits and had trouble ordering more because of the Columbus Day weekend. But the response was aided by shellfishermen, as well as officials and scientists in Maine and Massachusetts.

The state had to act fast because the stakes are so high for shellfishing, says DEM director Janet Coit.

“The reputation of our clams and oysters is superlative,” she says. “Our record of managing them carefully to ensure protection of public health underpins the value of our Rhode Island brand.”

If there has been any lingering fear about local shellfish, it isn’t having a noticeable effect. Clam prices didn’t drop after the scare, says quahogger Mike McGiveney, president of the Rhode Island Shellfisherman’s Association. Neither did oyster prices, says Russell Blank, owner of Rome Point Oyster Farm, an aquaculture operation in the Bay that sells its products through a larger state cooperative.

“The closure is an indication that our surveillance works,” says Robert Rheault, president of the East Coast Shellfish Growers Association. “It’s telling you that everyone is doing their job.”

Still, the state has upgraded its monitoring program in response to the scare. Until the bloom, the DEM collected samples at two locations in the Bay only between April and November, forgoing the winter months because cold weather discourages algae growth. Going forward, the agency has extended monitoring year-round to get a fuller picture of how species fare in all seasons.

Only two labs in the nation are approved by the federal government to test for domoic acid concentrations, one in Washington state and one in Maine. During the blooms last fall, samples had to be sent to the Maine lab for testing, which may have slowed the response in Rhode Island. The state’s health department can test for toxin levels at its own lab and is considering getting certified.

Meanwhile, Rhode Island Sea Grant is offering funding to scientists to do more research into Pseudo-nitzschia. Rhode Island officials are continuing to work with their counterparts in Maine and Massachusetts. They met in January in Providence and are set to get together again in April.

Smayda says that Rhode Island is moving in the right direction, but he wants to see a more comprehensive sampling program that covers the full range of water conditions that can contribute to blooms, similar to one he ran at URI from 1959 until funding ran out in 1996.

He suspects a link between the Pseudo-nitzschia bloom and the extensive rust tides that occurred just weeks earlier. He worries that they are signs of bigger changes taking place in the oceans.

“It’s actually an extraordinarily difficult problem to solve,” Smayda says. “You don’t know when they’re going to bloom. You don’t know how long they will occur or how intense they will be.”

“So,” he adds, “you better be on the alert.”

 

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