Red Tides on the Rise Worldwide
Scientists around the globe are studying the baffling increase in harmful algal blooms
WOODS HOLE, MASS. — DONALD ANDERSON opens a refrigerator and points to a flask filled with water and tiny rust-colored algae. "This one contains red-tide cells from Sweden," says the senior scientist in the Department of Biology at the Woods Hole Oceanographic Institution, here. "These cells are from China," he says, pointing to another flask. "We have cultures from all over the world."
This collection of algae is a small part of an international effort to study algal blooms, known as red tide because of the reddish tint the phytoplankton or algae give to the water.
Red tide became a household word in the 1970s and '80s when the blooms were linked with reports of people poisoned by eating tainted shellfish.
Since then, an increasing number of harmful algal blooms have occurred along coastlines in the United States and all over the world - in Norway, Sweden, Spain, Chile, Japan. China has declared red tide a national research priority and has asked for international assistance. Dr. Anderson, who is traveling to China this winter to start a joint research program, has worked on this problem for the past 17 years with funding from the National Oceanic and Atmospheric Administration (NOAA) Sea Grant program.
"There seems to be a global epidemic of blooms in the sea," says Theodore Smayda, a professor of oceanography at the University of Rhode Island in Kingston, R.I.
"They are suddenly appearing where there was no record of them before, and there is a spreading of new organisms."
Before 1972, only a few areas in the US were affected by dangerous algal blooms. Today, many more beaches have been closed to shellfishing, and the industry has lost millions in revenue. Scientists are discovering new algal species that are dangerous to humans.
Several whale fatalities are now linked to toxins in algal blooms. "Both juvenile and adult fish are dying off because the toxin is being filtered through the food web," Dr. Smayda says.
Fish farmers are also affected. Chaetoceros algae, one species of bloom, has long, thread-like spines. These spines break easily and enter a fish's gills, causing it to suffocate. Fish in pens can't swim away from the bloom, so fairly low levels of concentration can be fatal, says Rita Horner, oceanographer at the University of Washington School of Oceanography in Seattle.
Scientists are baffled as to what is causing the increase in red tides. Most say it is a combination of factors: escalating pollution, population growth, changing weather patterns, or even the dredging of the ocean floor, which disturbs dormant algae and causes them to grow prematurely.
Algae requires nutrients, such as nitrogen and phosphorus, to reproduce. Waste-water discharges, agricultural runoff, and pollution add these nutrients to the water, upsetting the ocean's natural balance.
"We are seeing both an increase in nutrients in the oceans and an increase in blooms," Smayda says. The two may be related, though a direct relation has not yet been proved.
"It could be an indication of something larger that is throwing the planet out of equilibrium, such as population growth," Smayda says. "People tend to use the oceans as a catchall, and they are blind to what this is doing to the seas."
Algae are transported throughout the oceans by currents. Ships also carry cells in water that gathers in their hulls, which often is dumped thousands of miles from where it originated.
Research on algal blooms has grown in the last six years, Smayda says. Before this, people didn't realize the seriousness of the problem.
Algal blooms have occurred naturally for billions of years and are an essential part of the oceans' ecosystem as a food and nutrient source. They primarily occur in the spring of the year.
"I believe one of the first recorded evidence of a red tide is found in Exodus (7:20, 21) when Moses touched the sea with his rod and it ran red with blood," says Anderson. "All the signs point to this, the red color, the fish dying, the smell."
While dozens of species can cause harmful red tides, thousands more are harmless, although they also give the water a red, brown, or orange tint, Anderson says.
"Red tide is a bad term because most people think of it as toxic," says Ms. Horner "There can be toxin in shellfish without colored water, and it is possible to have colored water without toxins." Some scientists even say that algal blooms could help reduce global warming. (See related story below.)
Shellfish can become tainted when toxins are consumed by these algae-eating organisms. Clams, for instance, siphon or suck water through "necks." They filter several liters of ocean water a day, extracting plankton particles from the liquid. Most shellfish cannot distinguish between harmful or harmless algae, and toxins can accumulate. Some shellfish rid themselves of the toxin over a period of time; others do not.
"Blue mussels will pick up a toxin very quickly and rid themselves of it within a few weeks," says David Whittaker, marine biologist in the Massachusetts Marine Fisheries Division in Boston. A surf clam, on the other hand, retains the toxin "forever," he continues. As far as it is known, these toxins have little effect on the clams.
ONCE a red tide occurs, the area is usually quarantined and the sale or harvest of resources restricted. When the danger is gone, anywhere from weeks to years, the area is reopened. George's Bank, a fishing ground off the coast of Cape Cod, Mass., has been closed for shellfishing since 1989.
Three years ago, surf-clam fisherman John Roberts harvested $750,000 worth of shellfish from George's Bank. "I always fished there," says Mr. Roberts. "Now I have to go all the way to New Jersey for clams, losing 20 to 25 percent in business. I only go to George's when the Massachusetts Deptartment of Health commissions me to do a survey [to check the level of poison in shellfish]."
A harmful bloom in a fish farm may occur after the aquaculture has been established for a while, Smayda says. Continually pumping fresh water into the pens or moving fish frequently to different locations can help prevent this from occurring.
The cost of red tides varies. For example, Anderson says, a 1980 outbreak in Maine cost the state $7 million for lost shellfishing. Korea's fishing industry lost $50 million one year because of red tide.
The Intergovernmental Oceanographic Commission of the United Nations Educational, Scientific, and Cultural Organization (UNESCO) assists other countries in dealing with harmful algal events.
"Many developing countries can't afford to monitor the shellfish, yet they can't afford not to eat the food," Anderson says. In the Phillipines, a posted contaminated area failed to deter people who had nothing but shellfish to eat, and six died, he says.
The group is organizing countries to share ships and equipment so scientists can exchange data, information, and assistance.
"In this country, our seafood is very safe in respect to this biotoxin," Anderson says. "Two people died eight years ago from PSP [paralytic shellfish poison], after ignoring quarantine warnings. This is tiny when compared to the amount of coastline we have.
The consumer confidence should be very high. There is a safety net out there. But one can't say the same for the rest of the world, especially developing countries."