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