Toxic algae specialist Don Anderson
The twisting warren of rooms in Don Anderson's lab has the beehive pace of a factory. In one nook a technician downloads data originating from a satellite high in space, while two other workers sit with their eyes glued to microscopes, tap-tapping counters, tallying thousands of cells. Down the hall, a visiting scientist from Spain experiments with antibodies, while in another room a graduate student works with DNA. The focus of their efforts are stored nearby in a bank of humming refrigerators containing jars of mud and hundreds of test tubes holding two ounces of seawater and a floating wisp of color. These are living cultures from around the world, an archive of tiny killers that can produce poisons 1,000 times more lethal than cyanide.
The killers are toxic dinoflagellates, members of a class of nearly 2,000 single-celled organisms found in the sea, lakes, and polar ice. The great majority of these algae are beneficial: One of the lowest links of the food chain, dinoflagellates are prey for zooplankton, and ultimately for fish, marine mammals, and human beings. But when conditions are right, dinoflagellate populations skyrocket, forming dense colored blooms that vividly stain the water they swim in and turn it opaque as paint. Most of these “red tides” are harmless, but they can turn catastrophic - when they stop growing and decompose they rob sea life of oxygen; when alive, some can produce toxins that accumulate in the tissues of animals that consume the algae as food, killing fish, birds, and marine mammals, and robbing humans of their memories, the use of their limbs, and their lives.
Although the first recorded red tide appears as a Biblical plague (“...all the waters that were in the river were turned to blood. And the fish that was in the river died; and the river stank and the Egyptians could not drink of the water of the river.” Exodus 7:20,21), the number of red tide blooms reported worldwide has taken a sudden leap.
“There has been a tremendous expansion over the last twenty years and it shows no signs of abating,” says Anderson, a tall, soft-spoken biologist who has focused on red tides, or harmful algal blooms (HABs), since the early 1970s.
Consider this: In two decades, reports of certain types of red tide, which formerly involved only the waters of Europe, North America, and Japan, now are reported in South Africa, Australia, India, Southeast Asia, and other sites in the Southern Hemisphere. In 1985, Aureococcus anorexefferens turned Long Island waters into a brown soup and all but destroyed the area's multi-millon dollar scallop industry. Two years later, more than one hundred people fell victim to an unprecedented outbreak of shellfish poisoning in Canada, with three dead and more than a score suffering memory loss. Scientists blame toxic Alexandrium for the 1987 death of fourteen humpback whales off New England that same year; simultaneously a huge bloom of the dinoflagellate Ptychodiscus brevis drifted from Florida to North Carolina, closing shellfish beds and sickening scores of residents and tourists.
Don Anderson is spearheading an assault on the red tide epidemic that has established WHOI as one of the world's leading centers of HAB research. His painstaking work has made his lab a Mecca to scientists and students from around the world.
“We take cruises into the coastal waters to find out the way the water's moving, and the way these toxic algae are growing and getting eaten,” Anderson says in his crowded office, where books and papers are piled high and e-mail arrivals regularly flash on his computer. “We grow them in the lab and look at how the nutrients we give them change the amount of toxins they produce. We're trying to find the genes that code for the toxin, and we're trying to make tests and kits to detect the toxins and the cells.”
“Don has shown stunning scientific leadership,” says Ted Smayda, Professor of Oceanography at the University of Rhode Island. “He has put himself amongst the avant garde in the discipline by his eagerness to acquire new approaches and new techniques. A lot of people play it safe, but Don keeps reaching.”
Part of his success, some colleagues say, comes from an uncanny ability to detect cause and effect, to see all the doors that open in the wake of each discovery. Others credit his doggedness, his unwillingness to rest until every potential challenge to a new solution has been disarmed. And more often than not, Anderson's persistence is warranted: “These cells,” he says, “are always fooling us.”
Despite their tiny size, dinoflagellates are enormously puzzling. Tinted with chlorophyll and other pigments, many can photosynthesize and are thus considered plants. However, they exhibit behavior normally associated with conscious creatures - they use their long, undulating tails and a waving belt about their middle to swim (dinoflagellate comes from the Greek dinos - to spin, and Latin flagellum-whip); some even eat their neighbors, and still others perform what seems to be a mating dance.
Like most single-celled algae, dinoflagellates reproduce by mitosis: Cells divide in two, the two into four and so on. With sufficient light, nutrients, calm waters and few zooplankton or larger animals to graze upon them, their numbers can quickly increase to millions of cells in a liter of water.
When nutrients are scarce, however, some species turn to sexual reproduction - cells split into male and female forms, which then fuse into one cell. “They form thick-walled dormant cells, called cysts, that settle on the seafloor and can survive for years,” Anderson says. “When favorable growth conditions return, the cysts germinate and reinoculate the water with swimming cells that can then bloom.”
The ability to swim as much as ten meters per day gives dinoflagellates a key advantage when the warm sun or freshwater run-off creates a buoyant surface layer above colder, denser, nutrient-rich waters. The swimming dinoflagellates reside on the surface during the day, “harvesting sunlight like sunbathers,” Anderson says.“They then swim down to take-up nutrients by night. Non-motile phytoplankton cannot easily get to the deeper layer.” The result is a sudden bloom in water that seems inhospitable to growth.
Researchers are unsure why dinoflagellates produce toxins. Some theorize toxins are self-defense weapons that incapacitate predators or cause the dinoflagellates to taste bad. Others think the toxins perform an essential biochemical function within the dinoflagellate and are only coincidentally harmful to other species. Scientists do know that the toxin that a species may produce can change with differing light levels, temperature, nutrients and water agitation.
The toxins enter the food chain when higher organisms consume the dinoflagellates. “Clams, mussels, oysters and scallops can ingest the algae and retain the toxins in their tissues,” Anderson explains. “Typically, the shellfish themselves are only marginally affected, but a single clam can sometimes accumulate enough toxin to kill a human being.”
Shellfish accumulate four types of toxins - when eaten by humans, they can cause paralytic, diarrhetic, neurotoxic, and amnesic shellfish poisonings, shortened to PSP, DSP, NSP and ASP. DSP causes diarrhea, nausea and vomiting. PSP prompts tingling and numbness of the mouth, lips and fingers, muscle weakness, and, in acute cases, respiratory paralysis and death. NSP triggers diarrhea, vomiting, stomach pain, muscle aches, dizziness, anxiety, and tingling in the limbs. ASP causes disorientation, stomach cramps and temporary or permanent loss of short term memory - ASP victims can remember their names and addresses, for example, but not what they had for lunch.
These algal toxins play havoc with the body's chemistry. They alter the ion balance within individual cells, disrupt electrical conduction across neural synapses and between nerves and muscles, and bring essential physiological processes to a halt. The memory loss that marks ASP occurs as the toxin domoic acid depolarizes brain neurons, kills cells, and causes cerebral lesions.
Illnesses and deaths from shellfish poisonings are rare in developed countries where monitoring programs routinely detect contaminated shellfish before they reach the market. Worldwide, however, shellfish toxins poison thousands and kill scores each year, while a related toxin, ciguatera fish poisoning, affects tens of thousands annually. In developing countries, the impoverished populations that depend heavily on the sea for food are especially vulnerable to red tide toxins, as are unsuspecting tourists.
But in both developed and developing countries alike, HABs are taking a rising economic toll. Shellfish and fish losses total tens of millions of dollars every year. And as the world's fishing grounds are picked clean and nations turn to aquaculture to meet consumer seafood demand, HABs are devastating finfish bred in coastal pens - while wild fish can swim away from algal blooms that might burst their blood cells or destroy their gills, penned fish are trapped. Within the last ten years, massive HAB-induced fish farm kills have become routine.
Anderson's own career proves that HABs are on the rise. Since his groundbreaking graduate work at MIT, his pace has constantly accelerated. “We're spending much more time dealing with new toxins in new parts of the world,” he says. “It's evidence of the global expansion that I feel and see personally every day.”
As yet there is no definite explanation for the rise in reported red tides. Some observers say improved monitoring and scientific advances are merely finding toxins and HABS that have always been with us. But some HABs are clearly the result of human activity. Freighters that use water for ballast suck up dormant cysts in one harbor and discharge them in another half way across the globe. Coastal dredging disperses buried cysts into currents that carry them long distances. And shellfish spat, shipped from place to place to seed aquaculture beds, carry hitchhiking dinoflagellates that colonize their new surroundings.
More worrisome is the increasing evidence that coastal development and its associated discharges of nitrogen-laden effluent stimulate dinoflagellate growth. Studies in the North Sea, Hong Kong, the Netherlands, and Australia link HABs to coastal pollution. Red tides in the sea of Japan mounted with rising population growth, then declined after local authorities mandated strict effluent controls. “HABs are a real sign to us that we are doing bad things to our water,” says Anderson. “We have abused our coastal waters, and one sign of that abuse is increased red tides.”
Anderson cautions that pollution is not the only culprit, and he says it will take another decade of research to fully clarify the causes. In the meantime, he and his associates in his hectic lab are running full-tilt to meet requests for help from around the world.
“There are so many places struggling with similar problems, countries that are not able to deal with issues the United States has taken for granted. I will eat shellfish here because I know our monitoring programs are safe, but that's not true in a lot of countries, and that's where they need help.” Anderson helps governments design training, monitoring, and research programs, and visiting scientists are always present in his lab, learning to grow cultures from cysts in the sediments, to isolate and culture dinoflagellates from crowded water samples, and to extract toxins and make analyses.
He recently completed a two-year project with the government of China, where many of the salt marshes, mangrove swamps, and wetlands have been uprooted for fish, shrimp, and shellfish farms, and red tides plague the coastline. And here at home, Anderson and colleagues from U.S. government agencies and universities have just put the finishing touches on a national plan to coordinate research, monitoring, and regulatory policies in the United States.
As his field has matured, Anderson's schedule has becoming increasingly fragmented. He spends more and more time as a laboratory administrator, research fund raiser, and policy advisor and less with the hands-on research he loves. He's increasingly on the road, away from his wife Kay, his young sons Brian and Eric, and his daughter Lauren. His itinerary for just the latter half of 1995 includes a conferences in Japan, policy meetings in France and Chile, and a stint at a Swedish marine station where he can, at last, devote an uninterrupted week to pure research.
Yet if he sometime laments the exhausting tug of war between the varied demands on his time, his sense of duty keeps him going. “Almost half of my working hours are spent doing things you can't call research, but which are helping my field progress in ways that are helping society,” he says. “I have a great job and am blessed with the opportunity to do exciting research. I owe it to my field to provide guidance and advice to those who are asking for it.”
Copyright © 2002 Tom Gidwitz