Second toxic algae bloom in some RI waters closes shellfishing

March 02--PROVIDENCE, R.I. -- The toxin-producing algae known as Pseudo-nitzschia was never a problem in Rhode Island until last fall. Now, less than five months after the algae bloomed in state waters for the first time, it's blooming again.

At sunrise on Wednesday, the Rhode Island Department of Environmental Management enacted a ban on all shellfishing in lower Narragansett Bay, the lower Sakonnet River and portions of Rhode Island Sound after mussel and quahog samples collected earlier in the week tested positive for elevated levels of domoic acid, the toxin sometimes emitted by Pseudo-nitzschia that can build up in shellfish meats and, when ingested, can sicken humans.

Even though domoic acid was detected in samples of clams and mussels during the bloom that started last September and stretched through much of October, subsequent tests found that the levels were well below the U.S. Food and Drug Administration standard of 20 parts per million.

This time, however, some samples taken from state waters on Sunday and Monday exceeded the standard. The levels in samples of mussels taken from four separate locations and quahogs taken from another location ranged from 14 to 32 parts per million, according to the DEM. The levels were generally higher in the sampled mussels, which tend to assimilate the toxin faster than other types of shellfish.

The DEM notified shellfishermen on Tuesday and the Rhode Island Department of Health followed up with seafood dealers, but it appears that no shellfish had been harvested in recent days from the waters that have been shut down.

"It seems like there hasn't been any harvest from the area of concern," said Angelo Liberti, chief of surface water protection for the DEM.

The DEM tested the shellfish for domoic acid after Massachusetts authorities alerted the agency late Friday afternoon to higher-than-normal numbers of Pseudo-nitzschia discovered in Buzzards Bay. Tests in Massachusetts for domoic acid came up negative.

The DEM would usually follow the same protocol as in Massachusetts and test for Pseudo-nitzschia numbers before sampling shellfish for domoic acid. But Liberti said the agency skipped ahead to save time. Domoic acid can cause amnesic shellfish poisoning, a condition that can include memory loss.

Tests of water samples collected from upper and mid-Narragansett Bay on Monday found a range of between 2,000 and 35,000 Pseudo-nitzschia cells per liter. The DEM generally steps up testing if more than 20,000 cells per liter are found.

During the fall bloom, Rhode Island officials were only able to test for the presence of domoic acid but had to send shellfish samples to a federally-certified lab in Maine to determine the specific levels of the toxin.

In the wake of that bloom, in an effort to speed up the state's response if similar incidents were to occur, the DOH came up with its own process to test for domoic acid levels.

That process was used this week, and, according to Health Department spokesman Joseph Wendelken, all the testing has been done in Providence, not in Maine.

In the coming days, the DEM and the DOH will collect additional shellfish samples from the affected waters and from waters unaffected by the announcement to further evaluate the bloom and determine whether the ban can be lifted.

Pseudo-nitzschia had been thought of as a type of algae that grows best in the fall, but Liberti said that a recent analysis of data from years of observation in state waters found that there are few constraints on when it can proliferate.

"It really can bloom anytime throughout the year," Liberti said. "But it was unexpected that [the toxin] showed up in shellfish."

akuffner@providencejournal.com / (401) 277-7457

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