link to Home Page

icon Seaweed Invasions

West Coast of U.S. Faces Deadly Giant Cloned Algae
Reuters, July 6, 2000

It looks like a soft carpet of vibrant green, rippling in the ocean's currents. But biologists call it an alien invader, a killer that strangles native sea plants, plays havoc with fish populations and causes ecological devastation in coastal communities. Having defeated the control efforts of France, Spain, Monaco and Italy to spread throughout the north Mediterranean, the Caulerpa taxifolia alga has been spotted for the first time in California waters - prompting a red alert among environmentalists and oceanographers watching for new threats to the region's delicate ecology. "In terms of potential damage, this species is a very, very serious problem," Robert Hoffman of the National Marine Fisheries Service said on Thursday. "It moves in and displaces anything that is normally found along the ocean bottom and becomes the one single species that dominates the habitat." Marine biologists identified the first North American sample of the species several weeks ago in eelgrass beds in a coastal lagoon about 20 miles (32 km) north of San Diego. Scientists say the lagoon infestation is an isolated case and stress there is no indication so far that the algae have spread into open ocean along the coast. But many marine biologists fear it is only a matter of time before the hardy water plants - originally engineered to look pretty in home aquariums - take hold in coastal waters, where they could imperil the eelgrass and kelp beds that form the basis of the region's marine ecosystem. "Once it gets out of control, it is really out of control," Hoffman said. "That's why we are moving as fast as we can."

Seaweed Smothers Marine Life Along Florida Coast
By Hillary Mayell, ENN News, June 11, 2000

It looks lovely, a meadow of undulating green plants anchored to the seafloor extending for miles. But the seaweed Caulerpa verticillata has become the oceanic equivalent of the blob that ate Chicago, spreading inexorably into new habitat off the coast of southern Florida and squelching the coral reef ecosystem that has flourished there for millions of years. The mat of Caulerpa is nearly 6 miles long and as much as a half-mile wide in waters 30 to 100 feet deep. The Caulerpa generates its own toxins, which makes it unpalatable to the herbivorous fish of the reef ecosystem. Plants and animals of the reef ecosystem that can't move eventually die. Larger fish such as grouper move in, searching for another food source. What once was a productive fishery and an ecosystem steeped in biodiversity is fast becoming an ever-expanding monoculture of waving seagrass. Caulerpa isn't your typical invasive species that is introduced to a new environment, becomes established and quickly begins to outcompete native species. Caulerpa has existed in the shallow waters off the coast of Florida for eons, growing in the nutrient-rich shallow waters of mangroves. Then, around five years ago, scientists began to spot patches of Caulerpa growing on an offshore reef in water about 95 feet deep. Since then the patches have grown to become an almost continuous mat of seaweed covering tens of acres extending from Palm Beach to Jupiter Inlet. And there's no end in sight. The seaweed has no natural enemy and thrives in the nutrient-rich environment. What changed the ecosystem from a low-nutrient environment that supports a high biodiversity ecosystem such as coral reefs to a monoculture is the hand of man, says Brian LaPointe, a marine ecologist born and raised along the Florida coast.