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Underwater Microscope Helps Prevent Shellfish Poisoning Along Gulf Coast of Texas

April 9, 2008

Through the use of an automated, underwater cell analyzer developed
at the Woods Hole Oceanographic Institution (WHOI), researchers and coastal
managers were recently able to detect a bloom of harmful marine algae in the Gulf of Mexico and prevent human consumption of tainted

Shellfish beds in parts of Texas have been closed for a month, though
they are expected to re-open in the next few days.

Working with Rob Olson and Heidi Sosik—plankton biologists
and instrument developers at WHOI—biological oceanographer Lisa Campbell of
Texas A&M University used their “Imaging FlowCytobot” instrument to detect
a substantial increase in the abundance of the algae Dinophysis acuminata in the waters of Port Aransas, Texas.

Dinophysis acuminata
produces okadaic acid, a toxin that accumulates in shellfish tissues and can
cause diarrhetic shellfish poisoning (DSP) in humans. DSP is not
life-threatening, but symptoms include nausea, cramping, vomiting, and
diarrhea. Cooking does not destroy the toxin in the shellfish.

The Imaging FlowCytobot, which is automated and submersible,
counts microscopic plants in the water and photographs them. The images and
data are relayed back to a shore-based laboratory, where specially developed
software automatically classifies the plankton into taxonomic groups.

“It is very satisfying to find that a technology we
developed as a research tool can be so effective for protecting human health,”
said Olson, who has worked with Sosik for several years to prototype and modify
flow cytometers, which are more typically used in many biological and medical

“We designed the Imaging FlowCytobot for continuous monitoring of
a wide range of plankton, and that turns out to be just what was needed to
detect a harmful algal bloom that no one expected.”

The discovery of the Dinophysis
bloom came while the researchers were actually looking for something else.
Campbell, Olson, Sosik, and colleagues deployed the instrument in the fall of
2007 at the University
of Texas Marine Sciences
Institute laboratory in the Mission Bay Aransas National Estuarine Research Reserve.

Their principal goal was to observe Karenia brevis, another toxic alga that blooms periodically in the
Gulf and can lead to neurotoxic shellfish poisoning. The research team would like
to observe the next K. brevis bloom
before it happens; such blooms are most common and most extreme in the Gulf of Mexico in the late summer and fall.

The team is
also working to catalog the types and relative abundances of marine plants in
the area throughout the year.

In mid-February 2008, Campbell
reviewed plankton images collected by the Imaging FlowCytobot and detected a
substantial increase in the abundance of the dinoflagellate Dinophysis, which occurs naturally in
ocean waters worldwide but not usually in harmful quantities.

“We have never
before observed a bloom of Dinophysis
at such levels in the Gulf of Mexico,” Campbell said.

After reporting the increase to fellow researchers in
coastal Texas,
Campbell and colleagues collected water samples to confirm that algal toxins
were present in the water.

Other researchers collected oyster samples and sent
them for toxin analysis at a U.S. Food and Drug Administration laboratory.

On March 8, the Texas Department of State Health Services closed
Aransas, Corpus Christi, and Copano bays to
shellfish harvesting and recalled Texas
oysters, clams, and mussels that had been sold between March 1-7.

A week later,
six other bays and estuaries along the coast were closed. As of April 11, most
shellfishing areas had been re-opened, and the Aransas, Copano, and Corpus Christi were
expected to re-open in a matter of days.

The bloom and subsequent warnings occurred just days before
the Fulton Oysterfest, a major shellfish festival in the region. At last
report, no shellfish-related human illnesses have been reported in Texas this spring.

“This is exactly what an early warning system should be,”
said Campbell.
“It should detect a bloom before people get sick. So often, we don’t figure out
that there is a bloom until people are ill, which is too late. The Imaging FlowCytobot
has proven itself effective for providing an early warning.”

“With time, we have come to see that the instrument has
obvious practical uses,” added Sosik. “It now appears ready to make the
transition from basic research tool to operative tool.”

Funding for Campbell’s
monitoring program and construction of the instrument was provided by the
National Oceanic and Atmospheric Administration’s Cooperative Institute for
Coastal and Estuarine Environmental Technology (CICEET).

Funding for instrument
development and earlier prototypes of the FlowCytobot and the Imaging Flow
Cytobot was provided by WHOI—through its Ocean Life Institute, Coastal Ocean
Institute, Bigelow Chair, and Access to the Sea Fund—and by the National
Science Foundation.

The Woods Hole Oceanographic Institution is a private,
independent organization in Falmouth,
Mass., dedicated to marine
research, engineering, and higher education. Established in 1930 on a
recommendation from the National
Academy of Sciences, its
primary mission is to understand the oceans and their interaction with the
Earth as a whole, and to communicate a basic understanding of the oceans’ role
in the changing global environment.