May 18, 2008
Brown Tide Algae Reappear in Great South Bay
By Jennifer Smith, Newsday, Melville, N.Y.
May 18--Brown tide, the algae that triggered the collapse of Long Island's scallop fishery, has reappeared in the Great South Bay for the first time since 2001 and spread farther west than ever before.
Aureococcus anophagefferens, the tiny plankton that causes brown tide, poses no known human health risks to those eating shellfish from affected areas. But researchers say it could harm what remains of the bay's hard clam population because it produces a chemical that, in high concentrations, makes it hard for clams and other bivalves to feed. Shade from the blooms could also kill off eelgrass beds -- crucial nurseries for juvenile fish and other marine life -- by blocking light needed for photosynthesis.
"It's somewhat of a surprise," said Christopher Gobler, an associate professor at Stony Brook University's school of marine and atmospheric sciences who specializes in brown tide. "There hasn't been a bloom in the Great South Bay since 2001, and even that wasn't very big," Gobler said, adding that historically, the most intense brown tide blooms have been around the Robert Moses Causeway.
Officials said it's too soon to tell what triggered this bloom, but generally brown tide tends to appear in Long Island waters when levels of dissolved inorganic nutrients such as nitrate, which is found in fertilizer, are low.
Most algae use inorganic nitrogen to grow. Scientists think brown tide is sometimes able to out-compete other algae because it can also use organic nitrogen, which comes from decaying marine plants and animals in the water column and from other organic matter in bay bottom sediments. When sediments in shallow waters such as the Great South Bay release nitrogen, it can influence water chemistry and a favorable environment for brown tide is created.
This year, concentrations appear highest in waters off West Babylon. Samples taken there last week by the Suffolk County health department showed about 1 million A. anophagefferens cells per milliliter, said Robert Waters, supervisor of the department's bureau of marine resources.
"That's enough to affect the shellfish," said Cornelia Schlenk, acting director of New York Sea Grant, which has funded research on brown tide.
Studies show growth of larvae and juvenile clams stops when cell abundance exceeds 150,000 per milliliter; beyond 400,000, and they begin to die.
"An adult clam can weather brown tide -- they don't grow during that period, but it doesn't necessarily kill them," Schlenk said. "But it can affect their larval stages and their reproduction."
That's a concern for the Nature Conservancy on Long Island, which has been trying to revive the Great South Bay's dwindling hard clam population at a 13,400-acre bay bottom preserve off West Sayville. The group has sowed more than 2.8 million "seed" clams there in hopes that greater density will boost reproductive success.
"We're hoping this doesn't have an impact on the seed clams," said Carl LoBue, a Nature Conservancy marine biologist who heads the project.
Another worry is the bloom's duration. Brown tide appears to decline when the water gets above 78 degrees, but it often returns in the fall and can linger for months, Waters said. Last year a brown tide bloom farther east, in Moriches and Quantuck Bays, declined in August but blossomed again in September.
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