Underwater flow cytometer detects harmful algae in coastal waters

April 22, 2008, Falmouth, MA--Through the use of an automated underwater cell analyzer dubbed the Imaging FlowCytobot, researchers and coastal managers have detected a bloom of harmful marine algae in the Gulf of Mexico, thus ensuring that people in the region don't get sick from eating tainted shellfish.

Working with Rob Olson and Heidi Sosik, plankton biologists and instrument developers at the Woods Hole Oceanographic Institution (WHOI), biological oceanographer Lisa Campbell of Texas A&M University used the Imaging FlowCytobot to detect a substantial increase in the abundance of the algae Dinophysis acuminata in the waters of Port Aransas, TX. 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. "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 acuminata 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.

"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 instrument development and earlier prototypes of the FlowCytobot and the Imaging Flow Cytobot was provided by WHOI and by the National Science Foundation.