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Harmful Algal Blooms: Back to Basics

September/October 1998

Blooms of toxic or harmful algae have occurred off U.S. coasts with increasing frequency over the last several decades, causing more than $1 billion in losses as well as severe human illnesses, such as paralytic shellfish poisoning. "We don't yet know why we're seeing more harmful algal blooms," says David Garrison, associate program director of the Biological Oceanography Program in NSF's Division of Ocean Sciences. "To answer that question we need first to understand how these algal species function and why they bloom."

In 1998, NSF will spend about $1 million on basic-science studies of the ecology of bloom-forming species. About half of this money supports ECOHAB (Ecology and Oceanography of Harmful Algal Blooms), a new interagency program that supports field, laboratory and modeling studies on harmful algal blooms.

Donald Anderson, a senior scientist with the Woods Hole Oceanographic Institution, directs a team of ECOHAB-funded researchers looking at the Gulf of Maine. Their objective: to unravel the dynamics of toxic Alexandrium blooms. "Physicists are working hand-in-hand with biologists," says Anderson, "because how water circulates through the Gulf is as critical to bloom formation as the life-cycle of the organism itself."

Two major currents transport water along the coast of the Gulf of Maine. The western current originates with freshwater from rivers north of Casco Bay. The eastern current starts with much colder water from the shelf of Nova Scotia, augmented by freshwater from the St. Johns river. In the relatively well-studied western section of the Gulf, researchers are able to zero in on possible seed beds or "initiation zones" of the toxic algae. Weekly cruises collect physical and chemical data as well as sediment and water samples in which scientists look for the cysts that constitute the species' infancy and that allow the team to track their movement and development.

In May, an Alexandrium bloom occurred--bad news for shellfishermen but good news for the researchers, who were able to confirm the role of Casco Bay as an initiation zone. In contrast, the team's approach in the less-studied eastern section of the Gulf consists of large-scale hydrographic surveys and sampling. The very different habitat there is likely to produce different Alexan-drium dynamics.

Gregory Doucette, of the Medical University of South Carolina and a member of Anderson's ECOHAB-Gulf of Maine team, is also working on a separate NSF-funded project to see if naturally occurring bacteria might play a role in regulating toxic algal blooms. Doucette's group is testing for algicidal activity, several hundred bacterial isolates that are associated with Gymnodinium breve blooms off the Florida and Texas coasts. So far, two of these isolates appear capable of killing G. breve. "The next task," he says, "is to identify the bacteria's active components and determine how they work. The hope is to get at least one of these model systems well characterized so that we can begin thinking about ways bacteria might be used to control and mitigate harmful blooms."

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