Red tides are not a new biological phenomenon. The Bible says the Egyptians were plagued by a blood-red tide that fouled the Nile and killed fish. Homer's "Iliad" reports similar woes, and the Red Sea is probably named after the noxious blooms.
The unicellular organism, called Pfiesteria piscida, has at least 24 guises it can assume in the course of its lifetime. It can also masquerade as a plant or lie dormant for years in the absence of suitable prey.
Armed with a voracious appetite and vast reproductive powers, the microscopic animal moves through coastal waters to kill fish and shellfish by the millions and to poison anglers and others, producing pain, narcosis, disorientation, nausea, fatigue, vomiting, memory loss, immune failure and personality changes. Its toxins are so deadly that people who merely inhale its vapors can be hurt badly.
"This thing has us scared to death," said Rick Dove, the expert who has been appointed to keep track of the Neuse River in North Carolina, part of a coastal estuary where the organism periodically goes on killing sprees. "This river is our lifeblood. If it goes belly up, everything goes belly up."
Anything but a rare organism, Pfiesteria has scores of toxic cousins that appear to be multiplying around the globe, mainly as algae but sometimes as zooplankton and, most conspicuously, as red and brown tides.
Record algae blooms
In the Chesapeake Bay, heavy inflows of freshwater this year already have led to record blooms of algae.
"I haven't seen anything like it," said Lawrence W. Harding Jr., an oceanographer with the University of Maryland who has been conducting aerial surveys of algae blooms in the bay since 1989. The algae blooms stretched to the Atlantic Ocean.
Record freshwater flows early this year coupled with snowmelt "loaded the bay up with nutrients," Harding said, producing some of the earliest and most extensive algae blooms he's seen.
"When we first began flying in March, we had red tides [algae] in and around the Bay Bridge and up toward the Patapsco River," he recalled. During spring, the midbay was clogged all the way to the Virginia capes with brownish blooms, he said.
Some ecologists believe there is a serious global epidemic of these marine microorganisms. They fear that their toxic tides may upset the natural balance of the oceans and are urging action to reduce the runoff of sewage and other nutritive substances that seem to promote the poisonous blooms. Other experts are more cautious, conceding that the number of reported incidents is up but withholding judgment on whether this is anything more than an upturn in a natural cycle, with more observers filing reports on the scourge.
A growing fear, intriguing but unconfirmed, is that nutrient runoff from human development, the heavy use of fertilizers and livestock farms is feeding the growth of the marauding swarms. If true, it bodes ill, given the global spread of the phosphorous and nitrogen from human sewage, animal waste and fertilizers that is increasingly polluting freshwater streams flowing into coastal estuaries.
"There's a correlation between increased nutrients in coastal waters and increased frequency of phytoplankton blooms," said Dr. Jane Lubchenco, a prominent ecologist at Oregon State University who studies the workings of the intertidal zone. "But that's not causation. It smells like it, but the evidence is skimpy."
More toxic than cyanide
Studies of the deadly blooms are accelerating, if only because the tiny killers have been found to harbor poisons 1,000 times more toxic than cyanide, strong enough to kill humans.
"People in Washington are beginning to realize that you can't attack this with Band-Aids," said Dr. Donald M. Anderson, of the Woods Hole Oceanographic Institution on Cape Cod, who is an expert on red tides. "Every single coastal state has this problem in one form or another.
"Everybody agrees that the impact and number of reported events are increasing," Anderson added. "At the very least, in many areas of the world we are adding nutrients in the form of pollution into coastal waters, and that seems to be producing more harmful blooms."
The suspicion is that natural cycles of bloom and bust are expanding into a global menace. For scientific sleuths, the challenge is to find clues that allow natural causes and cycles to be distinguished from ones that are altogether unnatural.
"The question is whether human effects are prompting an increase in the frequency, virulence or the types of organisms," said Dr. Peter Franks, a red-tide expert at the Scripps Institution of Oceanography in La Jolla, Calif.
Red tides, he noted, are only occasionally red, also appearing as orange, brown and even green. And they never occur literally as tides, which are the rises and falls of the sea. The preferred
terms for the phenomena are harmful algal blooms (which kill things), noxious algal blooms (which smell bad) and exceptional algal blooms (which are visually striking but do no direct harm). Unfortunately, even nontoxic blooms can kill marine animals by depleting oxygen in the water.
Moreover, the danger is entirely invisible at times. "The organisms are often in such low densities that there's nothing to see," said the Scripps Institution's Franks. "Almost every year, // we have red tides that are barely visible."
The main constituents of red tides are algae, an ancient group of primitive organisms dating to the first terrestrial life. The microscopic killers in most cases are algae that occur in the form of dinoflagellates, tiny unicellular organisms that usually photosynthesize and contain chlorophyll but that also have the animal-like trait of bearing twin tails, which whirl the organism forward.
Some dinoflagellates move vertically in response to light, living near surface waters during the day and diving toward the bottom to feed in nutrient-rich waters at night.
A bloom develops when the dinoflagellates photosynthesize and multiply rapidly, thriving on dissolved nutrients and sunlight. The toxins from their bodies in many cases appear to be defensive shields against zooplankton and other aquatic grazers.
Poison in one clam can kill
Harm to humans often occurs when clams, mussels, oysters or scallops eat the dinoflagellates and accumulate toxins. Typically, the shellfish themselves are affected only slightly, but a single clam can sometimes pack enough poison to kill a human.
In the past decade, the number of known dinoflagellate species that are toxic has risen globally, to 55 from 22. Outbreaks once found only around the coastal areas of Europe and the United States now occur around the globe, including near Asia and South America.
Unfortunately, scientists are discovering that dinoflagellates can attack humans not only indirectly, via shellfish, but directly. No example is more gruesome than that of Pfiesteria piscida.
The baffling case began in the late 1980s, when scientists in North Carolina puzzled over large fish kills in which the victims were often covered with open, bleeding sores. A battery of tests ruled out fungi, bacteria, heavy metals and pesticides as the culprit. Finally, after much research, a bizarre dinoflagellate was uncovered by scientists at North Carolina State University at Raleigh and was studied in detail by Dr. JoAnn M. Burkholder, an aquatic ecologist there.
Pfiesteria piscida turned out to be not just a new species in a new genus but a whole new family of life. It kills in fresh water or sea water, but it is deadliest in polluted brackish waters where the salinity is a little less than half that of the sea. Researchers have found that unlike most toxic algae, the dinoflagellates dispense their poisons directly into the environment, to paralyze their prey, rather than harboring them internally.
After Burkholder's co-workers got stomach cramps and other symptoms, she moved her research in April 1993 into a special room at the university meant to keep toxins isolated. But the facility leaked. Burkholder and her assistant, Dr. Howard B. Glasgow Jr., suffered a rash of illnesses, including nausea, vomiting, headaches, burning eyes, memory lapses, breathing difficulty, mood swings, impaired speech and skin lesions on their hands and forearms. During the last exposure, Glasgow was nearly overcome and ending up fleeing the facility on his hands and knees.
The lab was closed for more than a year, until July 1995, for sealing and strengthening. It was reopened only after close inspection by biological warfare experts from the Defense Department.
'On a par with AIDS'
"Now it's a biohazard Level 3 facility," Burkholder said in an interview. "That's above rabies and on a par with AIDS. We're erring on the side of caution. We want to make sure nobody gets hurt."
Burkholder has discovered that the microscopic organism has an arsenal of disguises that make it extremely difficult to track through its watery environment. Of its 24 known life stages, 19 have been connected to particular survival strategies, but five remain mysterious.
"It can transform from an amoeba to a toxic zoospore in two minutes," she said. "Nobody believed that until we had people come in and watch it. Nobody had seen that before in dinoflagellates."
The organism can stay hidden at the bottom of an estuary for years in its cyst stage, awaiting an unidentified chemical signal that says fish are nearby and prompts the dinoflagellate to come alive.
"The zoospores make toxins that are shed into the water, basically drugging the fish and making them lethargic," Burkholder said. "The toxins can rip a hole through the skin of the fish, causing bleeding sores, although some fish die so quickly that no sores develop."
In laboratory tests, Burkholder has shown that the dinoflagellate's growth and reproduction are stimulated by phosphate enrichment that is typical of the levels found in the Neuse and Pamlico rivers in North Carolina, which have been stricken repeatedly with large fish kills and are part of the nation's second-largest estuary, sheltered by the Outer Banks. Such enrichment seems to work indirectly, causing the multiplication of algae, which the dinoflagellates feed on in addition to fish.
Tied to manatee deaths
The killer also appears to be stimulated directly by human and animal sewage, which it uses for its metabolism. Politically and -- economically, this is a touchy subject because North Carolina has grown in recent years to become one of the nation's top hog producers and swine excrement is implicated in the fish kills.
"I was threatened twice last summer" by anonymous telephone callers, Burkholder said. "It was, if I knew what was good for me, I would drop the research - only more bluntly than that."
But she is continuing her research. "This is the only dinoflagellate known to have a life cycle this complex," she added. "Now that we know what to look for, I think we'll find lots of others."
Such detective work is increasingly common. After months of urgent research, scientists at the University of Miami concluded in July that a red-tide toxin caused by a different dinoflagellate was responsible for a record number of manatee deaths in Florida this year. The finding was hailed as a major step toward understanding the threats facing the manatee, a 10-foot endangered mammal famous for its gentleness. Of the 304 manatee deaths so far this year, 158 have been linked to red-tide toxins, with the rest stemming from such ordinary causes as infant mortality and old age.
If the red scourge is indeed spreading and caused by nutrients from human development, experts say, it is easy to envision a number of possible controls, like decreasing the runoff and nutrients going into rivers. In the United States, such work has been a high priority for years, though environmentalists fault the pace of remedial work by the federal government as too slow.
"Mitigation can run the gambit from better prediction, to pollution control, to improving strategies employed in agriculture," said Anderson, of Woods Hole. "If fish farmers know a red tide is coming, they can move cages."
Dove, the river keeper for the Neuse River, as well as a lawyer and former Marine colonel, said that all the signs in his area pointed to the problem's origin in the rapid growth of agribusiness and factory farms and that the logical solutions centered on them as well.
"This river's been out of whack since 1991," he said. "Around that same time, we got big in the hog industry. We don't know if that's the only problem. But we know that they're producing more fecal waste than all the people in the state of New York.
"This is one of the most beautiful rivers in the country," he added, speaking of the Neuse. "Now it's a great embarrassment. It should never have been allowed to get to this point."
» 2010: "Discovery of Algae’s Toxic Hunting Habits Could Help Curb Chesapeake Fish Kills"
» 2013: "Large Bloom of 'Red Tide' Stains Southern Bay"
» Cheseapeake Bay Foundation: "What is the Chesapeake Clean Water Blueprint?"