Algae bloom in Narragansett Bay good news for R.I. shellfish industry

By Alex Kuffner | Courtesy of the Providence Journal

At the Baird Sea Grant Science Symposium held in December, some fishermen complained that the dwindling algae blooms are making the Bay less productive than it used to be. But an unusually large algae bloom hit Narragansett Bay this winter that provided a rich food source for clams, scallops, and other shellfish.

 

NARRAGANSETT, R.I. — The annual algae bloom in Narragansett Bay was the largest on record this past winter and could fuel a spike in the coming months in the numbers of clams, scallops and other bottom-dwellers that feed on the microscopic plants.

Diatoms are the most common type of phytoplankton that is an important base of the marine food web and can grow rapidly in certain conditions to create blooms.

The unusually large size of the bloom measured by University of Rhode Island scientists bucks a trend in recent years that has seen a diminishing of the winter/spring proliferation of native, naturally occurring species of phytoplankton that form the base of the food chain for the Bay’s marine animals.

The annual blooms have shrunk over the last decade or so as tightened state regulations have forced wastewater treatment plants to reduce by half the amount of algae-fueling nitrogen that they release into the Bay. Warmer winters may also have contributed by allowing the growth of more zooplankton, tiny animals that graze on the algae before it sinks to the bottom.

The changes have sparked concerns by some fishermen that the Bay has become too clean and nutrient-poor to support lobsters, flounder and other species that live in the lowest reaches of the water column. Researchers, however, say that climate change is playing a larger role in driving out the cold-water species that have historically populated the Bay. URI hosted a symposium on the debate last December.

This year’s bloom started on Jan. 9 and continued through the rest of the month as the algae chains grew heavy enough to drop from the surface of the water and drift down. At its height, “the Bay was brown throughout,” said Candace Oviatt, oceanography professor at URI.

“The bloom was everywhere,” she said.

Russell Blank, owner of Rome Point Oysters, an aquaculture farm in the Bay, said the bloom was noticeable but it was hard for him to tell whether this year’s stood out for its size.

“It got pretty cloudy there for a while, and then it cleared right up,” Blank said. “That’s all food for the oysters.”

Oviatt, who has studied the Bay for decades, had predicted that the days of a significant winter/spring bloom were in the past.

“I am extremely happy to actually be wrong,” she said.

But the occurrence this year is likely an outlier, tied to large amounts of rainfall in October capped by an end-of-month storm that washed a buffet of nutrients into the Bay.

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