Banned algae shows up on U.S. West Coast
by: David McCormick, davidm@exn.ca
July 7, 2000
Sea-choking algae that has devastated ecosystems in the Mediterranean Sea has been discovered in the waters off Southern California. The green algae - called Caulerpa taxifolia - has evaded efforts by France, Spain, Monaco and Italy to destroy it and now biologists in the United States are acting quickly to prevent the spread of the plant in California's waters.
Marine biologists identified the algae in a small lagoon about 32 kilometres north of San Diego. While it remains isolated in the lagoon so far, scientists are worried that if the algae are not destroyed it will soon make its way into the open ocean where it will harm native undersea plants and animals.
"That's a real concern," says Robert Hoffman of the National Marine Fisheries Service. "So it's imperative that we do something as quickly as possible."
Scientists know how dangerous the plant can be by looking at its impact in the Mediterranean. Usually a native of tropical waters, a stronger, hardier clone of Caulerpa taxifolia was developed in the 1980s to decorate aquariums. Around 1984, a sample of the clone somehow escaped into the Mediterranean from the Oceanographic Museum in Monaco.
From an initial patch of only one square metre, the algae spread to over a hectare by 1989. Today, it has spread through much of the northwestern Mediterranean Sea. Scientists compare it to a big carpet of green turf that has been unrolled across the sea bottom, absorbing nutrients and bulldozing over native plants.
In areas where the algae is well established, it has overgrown and eliminated native seaweeds, seagrasses and reefs, destroyed recreational diving and had a costly impact on commercial fishing, effecting the distribution of fish and hampering fishing nets.
While scientists are not completely sure that the species that has shown up in the lagoon is the cloned version from the Mediterranean, Hoffman says it is fairly likely.
"It has all of the characteristics in terms of how quickly it is growing and the fact that it is there in very cold temperatures. The tropical, normal species wouldn't have been able to tolerate it."
The clone algae have defeated all efforts to eradicate it. It can grow up to three metres long and now thrives not just in shallow, tropical water but in colder and deeper water as well. And it's very resilient - it can live up to 10 days out of water and even a tiny bit broken off can regenerate into a new plant.
For all of these reasons, 100 scientists lobbied the U.S. government to ban the importation, possession and sale of the clone Caulerpa taxifolia in 1998. They were successful - last year the algae was declared a prohibited species under the U.S. Noxious Weed Act.
Yet, the algae still managed to find its way to the United States. Hoffman says it likely wound up in the lagoon when somebody who had it in their fish tank dumped the aquarium out into the lagoon.
"Or, it could've been that they were actually cleaning it out in their driveway and the water, along with a fragment of the plant, got into the storm drain system and was then dumped into the lagoon," he says.
Right now, Hoffman and other biologists are examining ways to destroy the plant before it can go any further. The plan is to isolate the algae by constructing underwater tarps over the areas it is established in and then treating it with a herbicide.
"Part of what we're doing right now is investigating the feasibility of this approach," Hoffman says. "And which herbicide would be the most appropriate and what dosage would be required."
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