Edition: U.S. / Global

Troubled Seas: Global Red Tides of Algae Bring New Fears

Published: May 3, 1988

LATE last August, off the coast of Naples, Fla., microscopic algae began to reproduce quickly, thriving and exploding in a matter of days into a huge toxic bloom that dominated the coastal environment.

Two months later, the same organism, Ptychodiscus brevis, invaded estuaries along much of the North Carolina coast.

It turned the waters yellow, devastated the fishing and tourism economy and caused 41 reported cases of respiratory, gastrointestinal or neurological illness in people who worked the normally productive waters or spent time on the area's beaches. North Carolina's bloom is believed to have traveled north in the Gulf Stream, bypassing other Southern states.

Some scientists describe it as the latest outbreak in what they say is a spreading global epidemic of toxic and nontoxic algae blooms, called red tides. More toxic tides are being reported worldwide, damaging coastal economies as they choke marine life and foul beaches. While they acknowledge that some of the increase may be due to better reporting, scientists are accelerating research to find out the causes, which may include climatic changes, natural growth cycles and pollution, particularly accumulated nutrients that may have finally glutted coastal areas.

''We are seeing a global first-order change,'' warned Theodore J. Smayda, a professor of oceanography at the University of Rhode Island.

Stressing that there appears to be a long-term degradation of coastal waters, Virginia K. Tippie, director of estuarine programs for the National Oceanic and Atmospheric Administration. said, ''If the natural environmental conditions are in the right sequence this year, we will continue to see some problems as we did last year.''

Until last year, North Carolina had never had a toxic algae bloom. Indeed, the Ptychodiscus organism had never even been seen north of Jacksonville, Fla., about 800 miles to the south. Other toxic tides have been reported off Suffolk County, N.Y., Rhode Island, Tasmania, Taiwan, Guatemala, Korea, Hong Kong and Venezuela.

In a scientific paper delivered at a symposium last year in Japan, Donald M. Anderson, an associate scientist at the Woods Hole Oceanographic Institution in Massachusetts, said that over the last two decades, scientists have seen ''a global increase in the frequency, magnitude and geographic extent'' of red tides.

''There's no question that the toxic species have been more noticeable recently,'' Dr. Anderson said in a recent telephone interview. ''But there is no way to really quantify what is going on. We have a general view over time that accumulates, but there is no doubt that in certain parts of the world we are seeing more of these toxic events.''

Scientists who study phytoplankton, the microscopic plants that when multiplied billions of times create algal blooms, are now trying to learn the cause of the blooms' increasing frequency and force.

Their ideas range from long-term climate shifts to human-caused changes like the flow of sewage and other nutrients into estuaries. Last week, the Environmental Defense Fund, a nonprofit environmental group, reported that the airborne nitrates in acid rain, which come mostly from motor vehicles, power plants and other industries, are also a major source of the nitrogen feeding algae blooms in Eastern coastal waters.

Another possibility, some wary scientists argue, is that the increase in blooms results from their being noticed more. The world's oceans are receiving closer scrutiny as they are used more and more for recreation, transportation and aquaculture. Pollution as Stimulant

Toxic algal blooms have occurred throughout history and can have natural origins. The idea that they could be encouraged by pollution is only now gaining favor with some scientists. ''It clearly was not a necessary factor in some of these algal events,'' Dr. Anderson said. ''What is changing is the recognition that although not necessary, pollution can stimulate certain species.''

The term ''red tide'' is used generically by scientists and others to describe any bloom, toxic or not, even though the algae that cause the tides can turn waters brown, yellow, green or other shades as well, depending on the makeup of the organism. Most algal blooms are not toxic to fish or people, even though the discolored and turbid waters can make swimming or fishing unpleasant. Problems Beyond Toxicity

But algal blooms that are not toxic to fish can cause enormous damage. As algae proliferate, they can block sunlight and force out other small organisms that are the start of the marine food chain. And as the algae die, sinking to the bottom, their decay begins to consume much of the water's dissolved oxygen that other marine life need. The other life suffocates.

''It hasn't clicked with people that we are overfertilizing the oceans to the point where they are choked,'' said Gary T. Burris, the chairman of Survival of the Sea Society, a nonprofit organization that is studying and documenting the decay of the oceans. ''I've seen lobsters caught by fishermen that have algae in their gills. They were choked and rotted.''