SAN FRANCISCO — Dr. Chela Zabin will not soon forget when she first glimpsed the golden brown tentacle of the latest alien to settle in the fertile waters of San Francisco Bay.
“I had that moment of ‘Oh God, this is it, it’s here,”‘ said Zabin, a biologist with the Smithsonian Environmental Research Center. “I was really hoping I was wrong.”
The tentacle in question was that of an Asian kelp, Undaria pinnatifida, a flavorful and healthful ingredient in miso soup and an aggressive, costly intruder in waters from New Zealand to Monterey Bay.
The kelp, known as wakame (pronounced wa-KA-me), is on a list of “100 of the World’s Worst Invasive Alien Species,” compiled by the Invasive Species Specialist Group. Since her discovery in May, Zabin and colleagues have pulled up nearly 65 kilograms of kelp attached to pilings and boats in the San Francisco Marina alone.
Every year the damage wrought by aquatic invaders in the United States and the cost of controlling them is estimated at $9 billion, according to a 2003 study by a Cornell University professor, David Pimentel, whose research is considered the most comprehensive. The bill for controlling two closely-related invasive mussels — the zebra and the quagga — in the Great Lakes alone is $30 million annually, says the United States Federal Aquatic Nuisance Species Task Force.
Many scientists say that San Francisco Bay has more than 250 nonnative species, like European green crab, Asian zooplankton and other creatures and plants that outcompete native species for food, space and sunlight.
“Here you’ve got a veritable smorgasbord of habitats from shallow and muddy to deep water,” said Lars Anderson, a lead scientist with the United States Department of Agriculture. The Oakland port ranks as the fourth busiest in the nation, and ships bring in tiny hitchhikers from across the globe to take up residence in the bay.
Most invasive aquatic species arrive stuck to hulls or as stowaways in ballast water. Wakame first arrived at the ports of Los Angeles and Long Beach in 2000, Zabin and other scientists said. A year later it had moved south into Baja California and north as far as Monterey Bay, where scientists in scuba suits yanked it off boat hulls and marina moorings.
“It’s just like gardening; you can pull out all the weeds you want, but there will always be that little dandelion seed that will sprout and recolonize,” said Steve Lonhart, senior scientist at the Monterey Bay National Marine Sanctuary. The kelp, which can grow 2 1/2 centimeters a day, could spread as far north as Canada before the water becomes too cold to sustain it, Lonhart said.
Native to the Japan Sea, wakame has now spread to the Mediterranean and elsewhere along European coastlines, and to New Zealand, Australia and Argentina, where the fetid smell of rotting kelp has kept beachgoers from parts of the coast.
Wakame harms native kelp, mucks up marinas and the undersides of boats, and damages mariculture like oyster farming.
Zabin and colleagues from nonprofit groups and state and federal agencies have been pooling resources and volunteers, donning scuba and snorkeling equipment and filling black plastic trash bags with the kelp.
But before trucking it to the landfill, Zabin plans to ship some to Texas. “I got an e-mail from a guy who wants to use it to make biofuel,” Zabin said. “Maybe he could just come and vacuum it up.”