Serendipity At Sea
New technology and a bit of luck help MBARI scientists understand toxic algae.
Thursday, September 14, 2000
Your high school chemistry teacher probably didn''t cop to the role that chance plays in scientific discovery. But Lady Luck has always helped science lurch forward, and marine scientists who specialize in toxic algae blooms have just become a bit indebted to that muse.
Last month, when a team of scientists boarded the research vessel New Horizon and set out into Monterey Bay intent on studying upwelling, the team happened upon--and ended up examining instead--a bloom of algae that produces a potentially lethal toxin. "You could not have possibly organized such an expedition," says Monterey Bay Aquarium Research Institute molecular biologist Chris Scholin.
Indeed, because the team''s goal was to study how upwells--upward surges of deep, cold ocean water--transmit nutrients into food chains near the surface, the team of 12 researchers included specialists who, when they found the algae bloom, were ready to track how the algae plume moved through the bay. It was extremely "fortuitous" to have all the right scientists in the right place at the right time, remarks Scholin--particularly because the team found things they wouldn''t have expected.
The bloom that the New Horizon team stumbled upon was Pseudonitzschia australis, an algae that produces domoic acid. Like other algae-produced toxins, domoic acid moves up the food chain when marine organisms, such as shellfish or zooplankton, consume the algae, and then fish and other organisms consume the shellfish and zooplankton. In animals, domoic acid affects the nervous system, causing disorientation and seizures that can lead to death. In humans, domoic acid poisoning has been known to cause permanent short-term memory loss (known as Amnesic Shellfish Poisoning), disorientation, diarrhea, vomiting and abdominal cramping. In one outbreak on the east coast of Canada in the late 1980s, it even resulted in death.
Pseudonitzchia blooms are naturally occurring phenomena. What''s surprising about the New Horizon findings is that there hasn''t yet been any known impact on animal or bird populations--this despite the fact that the bloom covered a large area (researchers found sea floor-to-surface patches of algae from the southern half of the bay all the way down to the Big Sur coast), and despite the fact that Scholin found the algae in incredibly high concentrations of one million cells per liter. Under normal circumstances, Pseudonitzschia is found in concentrations of fewer than 100 cells per liter.
"With the numbers Chris [Scholin] was bringing in, I expected massive death and destruction," explains UC Santa Cruz Professor Mary Silver, who studies how algal toxins move through food webs. She also notes that the New Horizon team found some anchovies that contained very high levels of the toxin. Anchovies and sardines have been known to transmit the toxin up the food chain to sea lions and birds.
In 1998, domoic acid from Pseudonitzschia was linked to the deaths of more than 50 California sea lions. Since June 23rd of this year, the Sausalito-based Marine Mammal Center has picked up 142 sea lions around San Luis Obispo, over 100 of which were having seizures associated with a Pseudonitzschia australis bloom in that area. To date, 56 of these sea lions have either died or been euthanized.
Silver and Scholin both speculate that the Monterey bloom has not been lethal because it simply did not produce very much domoic acid, despite its intensity. The seed for the bloom could have been different from that of the San Luis Obispo bloom, but Scholin thinks nutrient conditions are probably responsible for the discrepancy.
In any event, the California Health Services Department is still warning people not to eat any personally harvested shellfish, crab innards, sardines and anchovies from the Monterey Bay, and Silver cautions that marine mammals and birds may yet be affected. "There''s still huge numbers of diatoms [algae] lying on the bottom of the bay, and we don''t have toxicity numbers on this yet," she explains.
The "good news," Silver observes, is that "big blooms don''t necessarily mean big dangers." But she concedes that these new findings show that toxic blooms are more complicated than scientists realized. Scholin adds that if big blooms can be relatively safe, it also seems plausible that smaller, harder to detect blooms might be extra toxic given the right conditions.
Lady Luck dealt a winning hand to marine scientists last month, but luck can''t take credit for the technology that enabled them to track the Monterey bloom. Scholin points to the importance of a device called a drifter developed by MBARI biological oceanographer Francisco Chavez. By marking and tracking a particular mass of water, rather than just surface currents, the drifter enabled the New Horizon team to watch how the water column involved in the bloom circled around the bay. And a procedure that Scholin developed for identifying genetic signatures without the aid of a microscope was also instrumental in tracking the bloom. Prior to developing the test, which Scholin likens to a colorized pregnancy test, water samples would have had to have been brought back to the lab for study before the algae could be identified.
Scholin hopes to further develop his test so that it can be performed remotely in numerous locations to help predict toxic blooms.
Remote data collection would go a long way toward helping scientists answer these questions--and it would also go a long way toward reducing the power wielded by Lady Luck.