By TODD McLEISH/ecoRI News contributor
When a large bloom of harmful algae appeared in lower Narragansett Bay in October 2016, and again in early 2017, Rhode Island’s testing methods weren’t refined enough to detect it before the toxins produced by the algae had contaminated local shellfish.
That scenario isn’t likely to happen in the future, now that the Rhode Island Department of Health’s laboratories have acquired new instrumentation and analytical tests to detect the toxins early and to determine when they have dissipated enough so shellfish harvesting may resume.
“It’s an improved early-warning system so we don’t have to worry about future problems with harmful algae blooms,” said Henry Leibovitz, the chief environmental laboratory scientist at the Department of Health. “We’re trying to safeguard public health, safeguard our shellfish economy, and safeguard the state’s shellfish reputation.”
The new testing system was approved in September by the Food & Drug Administration’s National Shellfish Sanitation Program, which regulates the interstate sale of shellfish.
The 2016 and 2017 blooms, which Leibovitz said were the first harmful algae blooms to occur in Narragansett Bay, forced the closure of parts of the bay to shellfishing and required that some previously harvested shellfish be removed from the market. It was caused by the phytoplankton Pseudo-nitzschia, which, when concentrated in large numbers, can produce enough of the biotoxin domoic acid to contaminate shellfish and cause those who eat the shellfish to contract amnesic shellfish poisoning.
Another kind of plankton, Alexandrium, produces a biotoxin that can cause paralytic shellfish poisoning. Both Pseudo-nitzschia and Alexandrium occur in Rhode Island waters year-round, but they are only harmful when concentrations are high and the toxins they produce reach 20 parts per million.
According to Leibovitz, the state’s previous testing system was “a primitive screening test” somewhat like a pregnancy test: it could determine whether the toxins had reached the limit, but not how far over or below that threshold they were. And it wasn’t sensitive enough to detect the lower concentrations of the toxins that would signal that the bloom had dissipated and shellfish harvesting could begin again. To reopen shellfish beds to harvest, the state had to send water and shellfish samples to a private laboratory in Maine, the only lab in the country capable of conducting the test at the time.
Now that Rhode Island has an FDA-approved lab, it’s offering its services to nearby states.
The state’s Harmful Algal Bloom and Shellfish Biotoxin Monitoring and Contingency Plan directs the Rhode Island Department of Environmental Management to collect weekly water samples from areas of the bay where shellfish are harvested. The samples are tested in the Department of Health laboratory. If large numbers of harmful algae species are found, the plankton are tested to determine the concentration of toxins they are producing. If toxin concentrations are high, shellfish are then tested and a decision is made whether to close particular areas to harvesting.
The problem of harmful algae blooms has been an annual concern along the coast of Maine for many years, and scientists speculate that it could be a more frequent problem in southern New England in coming years, too.
“We think the problem is knocking on our door,” Leibovitz said, “and we need to be prepared for it, not only for public health but to protect our strong shellfish economy. Imagine the damage that would occur to our reputation if contaminated shellfish was identified as coming from Rhode Island. People have a long memory for something like that.”
Public awareness of the risk from harmful algae blooms was raised this year as a result of the months-long red tide in Florida, which killed fish and marine mammals and sickened many people. It was the result of a bloom of a plankton species that produces a toxin called brevetoxin, causing neurotoxic shellfish poisoning in people who eat infected shellfish.
What triggers the algae to bloom is what Leibovitz calls “the $60,000 question.”
“A lot of people are studying it, including some at the University of Rhode Island, and there are a lot of theories behind it, but there’s nothing conclusive. There’s speculation that the cleaner bay means that the harmful species don’t have the competition that they used to have, but that hasn’t been proven,” he said.
The bloom of harmful algae in Narragansett Bay in 2016 and 2017 led Rhode Island Sea Grant to fund research to try to answer some of the questions raised by the bloom. Researchers from URI and elsewhere are investigating whether bacteria that accompany the plankton may influence the amount of domoic acid produced; whether nitrogen from the sediments may fuel the blooms; and whether nutrients from outside the bay played a role.
“The fact that we had our first harmful algae bloom doesn’t mean we’ve had our last,” Leibovitz said, “not with it happening every year in Maine. But now we’ll be way ahead of the curve in recognizing when there’s a problem developing.”
Rhode Island resident and author Todd McLeish runs a wildlife blog.