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The Pfiesteria Scare

Tiny Plants Threaten Bounty of Seas

By Joby Warrick

Washington Post Staff Writer

Tues., Sept. 23, 1997; Page A01

When 162 dolphins washed up on Mexican beaches last winter, police suspected drug gangs of dumping chemicals at sea. Only months later did they find the real killers: billions of toxic one-celled plants that formed a poison net across Mexico's Sea of Cortez.

Farther north, the victims were hundreds of brown pelicans whose bodies littered Monterey Bay, Calif., beaches over a few weeks in 1991. That time, the culprit was an ordinary diatom, a microscopic creature regarded as harmless until it suddenly exhibited an ability to manufacture toxins.

From killer algae to mind-altering microbes, coastal areas worldwide are facing an unprecedented assault from some of the strangest creatures ever viewed under a microscope. While scientists in the Chesapeake Bay area investigate the causes of this summer's outbreak by the fish-killing Pfiesteria piscicida, other marine ecologists see the attack as part of a global epidemic, an uprising by a host of seaborne saboteurs capable of wreaking havoc on coastal economies and ecosystems.

Some, including pfiesteria, are newly discovered species. Others are spreading into new territories or picking up nasty new habits. All seem to thrive in waters that have become chemically enriched by pollutants from the land.

"Twenty years ago, these kinds of outbreaks were rare," Nancy Foster, a marine mammal biologist and director of the National Oceanic and Atmospheric Administration's national oceans service, said last week. "When we did see them, they were smaller in scale. Now they're all around the coast, and almost every state is vulnerable."

Indeed, few coastal states have been immune. Between 1972 and 1995, the number of U.S. beaches and estuaries with major, recurring attacks by harmful microbes more than doubled, from 16 to 36, according to a federally funded 1995 study. Similar afflictions are plaguing coastal cities around the world, scientists say, from Hong Kong's polluted harbor to the industrial ports along the Black Sea.

The invaders belong to the invisible universe of algae, dinoflagellates and other one-celled organisms that form the base of the food chain in the world's oceans. A minute fraction are known to produce neurotoxins and other poisons that can harm higher animal forms.

But in the last 20 years, scientists say, the natural balance seems to have shifted to allow those "hidden flora" to blossom in new and deadly ways. The study of the new outbreaks has added whole new chapters to taxonomy books and introduced terms such as "eutrophocation" (over-enrichment and oxygen starvation of waters) and "nutrient pollution" to the vernacular.

"In 1984, we knew of 22 species of harmful dinoflagellates; now there are more than 60," said JoAnn Burkholder, the aquatic botanist who was the first to link pfiesteria to fish kills along the North Carolina coast. "What we do know is they are cropping up mostly in poorly flushed bays and lagoons where there has been nutrient enrichment" -- from runoff with natural and artificial fertilizers from cities, industries, suburbs and farms.

Some of the outbreaks, such as the pfiesteria attacks in North Carolina and Maryland, have killed large numbers of fish and prompted the closure of waterways. As recently as last week, an apparently unknown species of toxic algae was suspected in the deaths of thousands of reef-dwelling tropical fish off the coast of southeast Florida. Many of the fish were covered with sores similar to those caused by pfiesteria.

Some microbes are a direct threat to people. In 1987, a sudden growth surge, or "bloom," of a toxic diatom near Prince Edward Island, Canada, killed three people and sickened more than 100 others who had eaten contaminated mussels. At least five kinds of seafood-borne illnesses are known to be caused by toxic algae, two of which are potentially fatal to humans. One of them, amnesic shellfish poisoning, can cause neurological symptoms such as disorientation and memory loss.

Other toxic outbreaks have decimated wildlife populations. In Florida two years ago, for example, an enormous "red tide" of toxic one-celled dinoflagellates wiped out 304 manatees, the endangered walrus-like sea cows beloved by tourists.

This year, the toxic algae attack that destroyed scores of dolphins in Mexico's Sea of Cortez also killed a sea lion and at least four whales.

Concern about the apparent escalation of microbe attacks led to the recent creation of the Ecology and Oceanography of Harmful Algal Blooms research center, or ECOHAB, which is funded by several federal agencies and has the task of investigating the phenomenon. While scientists cite strong circumstantial evidence that links human pollution to the recent outbreaks, they acknowledge that a cause has not yet been established.

Indeed, they say it is likely that the explosion of newly discovered toxic species is partly attributable to the increase in the number of scientific observers.

"Ten years ago, people started realizing these things were out there, and so more grant money is being spent to find them," said Stuart Hurlbert, a biologist with San Diego State University. "It put people in a detective frame of mind."

But there also are clear signs that humans have reshaped coastal environments in ways that favor some of the toxic creatures. Probably the biggest single change is the ever-growing volume of nutrients -- waste from sewage plants and factories as well as runoff from farms, lawns and city streets -- in coastal waterways.

Burkholder said she believes that those pollutants create a perfect environment for pfiesteria, which seems to prefer stagnant, nutrient-rich waters. After a wet winter, the nitrogen and phosphorous flushed from fields and streets can apparently trigger a population explosion of pfiesteria in its nontoxic stage, she said. During the summer, when fish are abundant, pfiesteria blooms and attacks in toxic concentrations.

Other causes may be more subtle. Some scientists suspect that global warming is increasing water temperatures, inviting microbes to move into new territories. In addition, aquaculture, or commercial fish farms, and dam construction can cause a shift in the balance of microscopic species that compete for living space in every teaspoon of water.

For example, in the case of fish farms, large numbers of captive fish eat a proportionately larger number of zooplankton. In doing so, they remove more of the tiny aquatic herbivores at the second tier of the food chain that normally feed on smaller algae in the water supply moving through the farms. "When you take the cows away, the grass gets longer," said Peter J.S. Franks, a biological oceanographer at the Scripps Institution of Oceanography in La Jolla, Calif.

Franks, who has studied the "red tide" phenomenon, said he believes that the increase in harmful algae blooms was "probably inevitable" given the rapid growth of coastal cities during this century. But, like many scientists, he holds out hope that the same human ingenuity that created the cities can discover ways to control toxic algae outbreaks.

"Humans didn't cause red tides or algal blooms. They were here before we existed," he said. "Are we making them worse? The answer is probably yes. Can we do more to mitigate their toxic effects? The answer is yes -- probably."

© Copyright 1997 The Washington Post Company