June 20, 1995 Contact: Chris Woolston or Robert Irion (408/459-2495)
TOXIC ALGAE FOUND IN MONTEREY BAY FOOD WEB
FOR IMMEDIATE RELEASE
SANTA CRUZ, CA--Pelicans and cormorants often gather in shallow water near Santa Cruz. But in the summer of 1991, one such gathering took a bizarre and tragic twist. The birds seemed intoxicated, swimming in circles and squawking pitifully. Over the next few weeks, more than 100 carcasses of seabirds washed ashore near Santa Cruz.
After an intense search, scientists eventually identified the culprit: a natural poison never before detected in California waters. Now, researchers at the University of California, Santa Cruz, have discovered that the algae responsible for the poison are regular inhabitants of Monterey Bay. It appears the poison can spread throughout the food chain, from mussels and clams to fish and seabirds--and potentially to humans.
The poison, domoic acid, is produced by a marine phytoplankton species, Pseudo-nitzschia australis. In strong doses, domoic acid can cause severe stomach distress, brain damage, and even death. In 1987, more than 100 Canadians on Prince Edward Island became seriously ill after eating mussels tainted with domoic acid. Several patients developed dementia and amnesia. Four died.
David Garrison, an associate research biologist at UCSC's Institute of Marine Sciences, says a similar catastrophe is unlikely in Monterey Bay. However, he says, domoic acid still has the potential to cause human health problems. "We're not saying this will happen, but you can't rule it out," he says.
The chief causes of concern: Domoic acid is surprisingly common in Monterey Bay, and it spreads quickly. Algae such as Pseudo-nitzschia form the base of the food chain, and each animal in the chain can pass the poison to the next link. Graeme Haywood, a graduate student at UCSC, has found domoic acid in every animal species he has investigated, including several types of zooplankton, eight species of fish, mussels, and clams.
Garrison sees a need for increased awareness of the health risks of domoic acid. The California Department of Health Services currently monitors mussels for domoic acid, but Garrison feels their methods aren't sensitive enough. "We can find the toxin in the algae when they can't detect it in the mussels," he says.
Garrison believes that commercial seafood on the West Coast is adequately monitored for domoic acid. However, he says, the pismo clams, anchovies, sea scallops, and rock crabs that end up in sport fishermen's buckets might pose a health risk. These animals are not tested for domoic acid, and researchers don't know how much poison the animals might retain. Also unknown are the possible health hazards of eating low levels of domoic acid over long periods of time.
Once researchers realized Monterey Bay supported a potentially toxic species of algae, they started carefully following its growth patterns. Garrison and his graduate student Peter Walz have regularly found Pseudo-nitzschia australis in Monterey Bay waters. Over the last three years, the algae have bloomed about twice a year, with each bloom lasting one to three weeks.
Walz and Garrison were surprised to find that one recent bloom didn't seem to produce domoic acid. They suspect the bloom consisted of a nontoxic strain of Pseudo-nitzschia, but it's possible the algae turn the poison on and off in response to unknown environmental signals.
Haywood, who studies under professor of marine sciences Mary Silver, took research back through time by searching for domoic acid in preserved samples dating as far back as 1977. He says the bay has been tinged with the poison at least twelve out of the last seventeen years, and he's confident that it was present long before 1977.
For one thing, Haywood says, birds have become sick and demented several other times in the history of Monterey Bay. Perhaps the most noteworthy event occurred in 1961, when flocks of shearwaters began madly attacking residents of Rio Del Mar. "That looks very much like a domoic acid event," says Garrison. Soon afterward, Alfred Hitchcock announced plans to turn the incident into a movie--yes, it appears that "The Birds" suffered from domoic acid poisoning.
The impact of the poison apparently depends both on the size and the timing of the bloom, says Silver. The deadly bloom in 1991 was larger than normal, and it coincided with the arrival of schools of anchovies in the bay. The anchovies ate the algae, and the cormorants and pelicans ate the anchovies. "A series of events has to happen for there to be a real problem," she says.
Several major questions about domoic acid in Monterey Bay remain. Researchers don't know what triggers blooms of Pseudo- nitzschia or why the algae produce the toxin. Garrison says frequent, careful measurements of the blooms is the first step to answering these questions.
Other UCSC researchers have taken different approaches to studying domoic acid. Ronald Tjeerdema, an associate professor of chemistry and biochemistry, is studying how mussels, crabs, and anchovies accumulate the toxin. Chris Scholin, a visiting researcher at the Institute of Marine Sciences, is developing a genetic test that will allow scientists to detect Pseudo-nitzschia cells quickly and accurately.
Garrison and Silver's research is supported by California Sea Grant.
Editor's note: You may contact David Garrison at (408) 459-4789 or
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