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An Underwater Fight Is Waged for the Health of San Francisco Bay

A costly intruder from Asia, known as wakame, has arrived in San Francisco’s fertile waters, threatening native kelp, marinas, boats and mariculture like oyster farming.

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, Dr. Zabin and colleagues have pulled up nearly 140 pounds 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.

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