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Frontiers
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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