Toxic Seafood

The hunt for ciguatera is on in the Gulf of Mexico

Marine scientist Dr. Tracy Villareal has discovered that oil platforms peppering the Texas Gulf coast could be acting as the perfect incubator for ciguatera, the most common form of seafood poisoning in the world.

Ciguatera affects up to 500,000 people every year worldwide, but cases are still rare in Texas and the United States, says Villareal, associate professor at the Marine Science Institute (MSI). The illness, found primarily in the tropics, causes nausea, vomiting, teeth pain, numbness, prickliness, and a reversal of hot and cold sensations. Occasionally, ciguatera is fatal.

People get ciguatera after eating fish loaded with a toxin produced by a tiny, one-celled dinoflagellate called Gambierdiscus toxicus. The soft and muddy bottoms of the Texas coast are not good habitat for G. toxicus, which likes to grow on hard surfaces in warm waters.

“But when you get an oil platform sticking-up into the clear blue water, you get corals growing on them,” explains Villareal. “The coral is an indicator of the type of water conditions and habitat G. toxicus prefers. It’s enough of a coral community that the ciguatera dinoflagellates are there.”

Villareal found the dinoflagelletes growing on one hundred percent of the Gulf oil platforms he sampled in summer 2005, but he says that doesn’t mean they’re currently producing toxin.

“No one really knows what turns on a ciguatera event,” he says.

As part of a study funded by the National Oceanic and Atmospheric Association’s ECOHAB program, Villareal is growing G. toxicus in his Port Aransas lab to determine what environmental conditions might cause them to produce toxin.

Ciguatoxin turns up in fish on our dinner plates because it passes up the food chain from the dinoflagellates to the fish that we like to eat. Fish like barracuda, snapper and grouper accumulate the toxinmuch the same as mercury or DDT. These fish, and the fishers who seek them out, are drawn to the artificial reefs growing on the oil platforms.

To find out if fish from around these platforms are harboring the toxin, Villareal collected barracuda brought in by fishers competing in the Summer 2005 MSI Barracuda Hunt. He and his collaborators are analyzing a heap of barracuda—a total of 169 fish weighing-in at 1.2 metric tons—for the presence of the toxin. “The initial results show that we can measure ciguatoxin in some of these fish,” says Villareal.

Regardless of the direct threat to Texas fishers, Villareal says that ciguatera could become more of a problem throughout the United States. “More and more reef fishes are being exported to the higher latitudes and they’re exporting the toxin, too,” he says. “It’s a real interesting problem that the developing world is exporting to the developed world.”