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Molecular probes link sea lion deaths
to toxic algal bloom

Wednesday, 5 January 2000 at 11:00 U.S. Pacific Time

Media Contact:
Debbie Meyer, Communications Coordinator
Monterey Bay Aquarium Research Institute
(831) 775-1807,

MOSS LANDING, California—New molecular probes used to identify toxic diatoms allowed researchers to link a bloom of these algae to the deaths of more than 400 California sea lions in Monterey Bay during May and June 1998. Dr. Christopher Scholin, a molecular biologist at the Monterey Bay Aquarium Research Institute (MBARI), and colleagues report their research results in the 6 January issue of the journal Nature.

Harmful algal blooms in the ocean result from the rapid growth of some species of microscopic algae that produce toxic by-products. These toxins can cause public health threats and fisheries closures when transferred up the food chain, but the connection between algal blooms and marine mammal mortality has been difficult to establish. Traditional techniques used to identify the presence of potentially toxic algae work after the bloom has occurred and may even miss the bloom. In this study, the bloom of the diatom Pseudo-nitzschia australis and its associated neurotoxin domoic acid was first noted in plankton samples using DNA probe tests developed by MBARI and a toxin test developed by scientists at the National Oceanic and Atmospheric Administration’s Marine Biotoxin Research Program in Charleston, South Carolina.

"The DNA probes and toxin tests detected the short but significant bloom in Pseudo-nitzschia australis," said Dr. Scholin. "Our early alert and collaboration with marine mammal scientists and public health officials helped us collect the data needed to connect the sea lion deaths with the bloom."

australis1_scholin95.jpg (8542 bytes)

australis2_scholin95.jpg (7283 bytes)

A sample showing several species of the genus Pseudo-nitzschia as seen under a light microscope. The toxic species Pseudo-nitzschia  australis identified in the same  sample by the glowing DNA probe.

These techniques, in which species-specific DNA probes bind to the RNA of the toxic algae and glow when viewed under a microscope, could be applied using a robotic device in the field. Dr. Scholin and colleagues at MBARI plan to deploy a prototype of such a device in Monterey Bay this summer.


Note to media: Images and footage available on request.

Additional research contacts:
Dr. Chris Scholin, Monterey Bay Aquarium Research Institute,
Dr. Frances Gulland, The Marine Mammal Center, 415-289-7370
Dr. Gregory J. Doucette, Marine Biotoxins Program, NOAA-NOS,