Red Tide

As visitors make their way to the South’s famous beaches this summer, they may be in for a poisonous surprise. Populations of tiny algae are exploding in coastal waters around the region, causing phenomena called “red tides” that kill sea life and sicken people.

“The algae that cause red tides produce a toxin that kills fish and the fish wash up on the shore,” says Ed Buskey, a Professor at the University of Texas’ Marine Science Institute at Port Aransas. “They also release an aerosol that causes people’s eyes to water and nose and throat to sting. Red tides can particularly aggravate people with respiratory problems.”

Gymnodinium breve, one of many tiny algae that can poison fish and cause illness in humans, is the most common cause of red tides in southern waters. Under the right conditions, the G. breve algae become active and quickly reproduce, producing a reddish-colored toxic “bloom.” Scientists say a number of events may trigger the sudden bloom, including weather and water temperature, but nutrients found in animal waste and fertilizer that wash into waterways are also possible culprits.

The issue of whether red tides are on the increase and whether human activity is the cause is a matter of hot debate for scientists. “There’s some evidence of an increase in frequency of red tides due to growing coastal population, development, nutrient run-off, and pollution,” says Buskey. “It’s a logical hypothesis, but it hasn’t yet been proven.”

In North Carolina, researchers have found evidence for links between runoff from hog farms and blooms of another toxic algae called Pfiesteria. Florida studies are underway to determine whether there is a similar connection between nutrients and G. breve red tides.

While red tides may be on the increase, they are nothing new in the South. Native Americans marked the seasons by fish kills, and Spanish conquistadors noted dead fish and discolored water in the Gulf of Mexico as early as 1530. Though red tides have been recorded in other parts of the country, they have been particularly devastating in the South in recent years, killing millions of fish as far north as North Carolina, along the Atlantic coast of Florida, and into the Gulf of Mexico.

Florida may be the state worst hit by red tides, with one occurring almost every year. In 1996, red tides killed 10 percent of Florida manatees and 162 dolphins, and cost the Sunshine State an estimated $40 million in losses from the fishing industry and tourism. With each red tide, shellfishing beds are closed, but occasionally affected shellfish is harvested and can cause stomach problems and numbness in people who eat it.

To find out more about what causes red tides and ways to control them, citizens and scientists are working together. ECOHAB, a federally funded project, was developed by Florida scientists and supported by a citizen’s group called Solutions to Avoid Red Tide (START) to examine the formation and transport of red tides.

“START has worked to lobby the state and federal government to get funding to find out how and why red tides are initiated,” says Jeremy Whatmough, President of START. “We want to find ways to control red tides that are environmentally friendly.” Efforts at control have included using clay to disperse the blooms and skimming dead, algae-poisoned fish off the surface of the water.

But mechanical dispersal and cleanup do not attack the root causes of the red tides. If the problem is linked to human farms and sewers, solving it may take years of grassroots work to change policy and practices. “People need to be educated,” says Buskey. “This isn’t going to go away overnight.”