"Foreign Species Invade San Francisco Bay"

"California is cracking down on invasive species, and that could have a big impact on national regulations due out later this year. The state has passed the strictest rules in the country to prevent cargo ships from bringing foreign plants and animals to San Francisco Bay. But the standards are so high, California may not be able to enforce them.

Trucks and cranes spring into action as a 900-foot container ship docks at the Port of Oakland. Every year, thousands of ships pass under the Golden Gate Bridge. They bring cars, sneakers, computers — and exotic organisms.

Biologist Andrew Cohen of the Center for Research on Aquatic Bioinvasions sees four of them. He slogs through a muddy beach in the eastern Bay Area and scoops up a clump of seaweed that's home to clams and snails. Cohen also spots some yellow dots, and he says they are "the egg mass of a Japanese sea slug which showed up here a few years ago."

Biologists have found hundreds of invasive species in San Francisco Bay, which Cohen says makes it one of the most invaded estuaries in the world."

Lauren Sommer reports for NPR's All Things Considered May 11, 2011.