Published on July 15th, 2009 | by Derek Markham2
San Francisco Bay Overrun by Alien Seaweed Forest
When you think of wakame (if you do at all), you’re probably imagining miso soup or a macrobiotic diet, but this variety of kelp (Undaria pinnatifida) is one of the world’s worst invasive species. Native to Japan, China, and Korea, wakame was found to be inhabiting New Zealand about 20 years ago, and recently has been making itself at home in coastal areas of Europe. San Francisco Bay is its latest victim, and the alien seaweed is posing a threat to native species there.
“The kelp is a serious threat to our native species because it crowds them out and deprives them of oxygen, so it ruins the natural habitat for native species of fish, shellfish, sea otters and other marine organisms.” – Chela Zabin, ecologist with the Smithsonian Environmental Research Center
Wakame is believed to have been introduced accidentally via ballast water and on hulls from ships arriving from Asia, and because it grows so quickly – up to an inch a day – and reproduces from spores, the plant can become a real problem for local marine ecosystems.
The seaweed species has been found invading harbors and estuaries along southern California since about 2000, but before the San Francisco Bay discovery, scientists believed that Monterey Bay was the northern-most location of wakame’s invasion. Until funding ran out in the last year, divers cleared Monterey Bay of the seaweed every six months.
Divers in the San Francisco Bay have been removing wakame growing from docks and ship hulls in a bid to keep the alien seaweed from releasing spores and spreading even further in the Bay. And even though the idea of free food in the Bay seems good, people are being warned not to consume any wakame harvested there, as it absorbs toxins present in the waters.
Image: jlastras at Flickr under CC License