By TODD McLEISH/ecoRI News
contributor
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.
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.
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 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.
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.
