U.S. ban urged for alien alga.

France, Spain, and Australia have banned the possession of the aquarium-bred Caulerpa taxifolia out of fear that accidental releases of this seaweed into open waters could lead to the ruin of local ecosystems, much as it is overtaking and smothering the northern Mediterranean seafloor. Last month, 107 ecologists and exotic-species research scientists petitioned the Interior Department to institute a similar U.S. ban on the alga.

"It seems pretty clear that the Monaco aquarium was responsible for introducing this [alga] into the Mediterranean," says petition organizer Andrew N. Cohen of the San Francisco Estuary Institute in Richmond, Calif. Because even a shard of the seaweed can spawn a new specimen, C taxifolia rapidly established itself in the Mediterranean, the petition notes, forming "monoculture stands whose impact has been compared to unrolling a carpet of Astroturf across the bottom of the sea."

U.S. regulators are aware of the seaweed's threat and are exploring ways to ban it, says Robert Peoples of the U.S. Fish and Wildlife Service in Arlington, Va. The Nonindigenous Aquatic Nuisance Prevention and Control Act of 1990 probably offers the best legal basis for such an action, he says. He expects that in a few weeks, the task force that decides what species to list under the law will consider adding this alga. If a case can be made that its introduction would be deleterious, a ban might be possible "in 6 months or even less," Peoples says.

That's none too soon, Cohen says. A report he prepared to accompany the new petition lists 244 organisms that have been transported by the aquarium trade and released into U.S. waters outside their native range--in many cases, allowing species free of predators to endanger or extinguish native species.