It came from beneath the sea

Mature Undaria pinnatifida with
crinkled, fingered shape
and sporophyll present at
base of stem

Photo: Marine Invasions
Research Laboratory at SERC

The California Coast has been invaded by a large brown marine inhabitant, just like in the 1955 horror flick, It Came from Beneath the Sea. The “creature” arrived through the Golden Gate despite efforts to hold it back, ready to wreak havoc in our bay. It’s not a giant, radioactive octopus like in the movie – it’s Undaria pinnatifida, a quick-growing, nonnative kelp.

More commonly known as Asian kelp, the large brown seaweed can grow six feet long in just two months, topping out at about nine feet. Its rapid growth is what makes it a danger to native species and to local harbors – it can easily colonize both natural and manmade surfaces. It not only overtakes rocky substrates, but it can quickly mire docks, pilings and vessels. If it gets a foothold in a tidal basin, it can create large kelp forests that block out the sunlight necessary to sustain native kelp and other marine algae and wildlife.

A single mature specimen can produce millions of spores a year, making it difficult to contain once it is within shipping channels. While native to Asia and Japan, it has already hitchhiked its way across the oceans to Europe, New Zealand, Mexico, and now California.

Undaria pinnatifida first appeared in California in 2000. From a localized sighting in Long Beach Harbor, it spread to Monterey Harbor by 2001. Researchers from the Smithsonian Environmental Research Center (SERC) in Tiburon found the first evidence of U. pinnatifida north of Monterey last May – at Pillar Point Harbor in Half Moon Bay and inside our bay at the San Francisco and South Beach Marinas.

Asian kelp is distinguishable from native species by its brown color and crinkled texture. Mature samples have differentiated blades with “fingers” and a ruffled, spiraling reproductive structure (the sporophyll) that forms around the main stem – native species don’t have this structure. Both young and adult forms also have a mid-rib, which is not present in native kelps.

With the cooperation of harbormasters, scientists from SERC, UC Davis, the Monterey Bay National Marine Sanctuary, NOAA, the California State Lands Commission, and U.S. Fish and Wildlife have been working to remove the kelp by hand from infested marinas.

On Saturday, Aug. 21, you can join an Undaria removal party at the San Francisco Marina. Meet at 9 a.m. in front of Gate 14, which is in the East Basin next to Fort Mason Center (a.k.a. Gas House Cove). Volunteers will work until noon or 1 p.m. removing kelp from floating docks and recording data. It’s recommended that you dress in layers (in something that can get dirty), wear sunscreen and a hat, and bring your own water and snacks.

Another removal party is scheduled for Saturday, Aug. 28 at South Beach Marina. Volunteers should meet in front of the harbormaster’s office. Please RSVP for either event to 415-435-7128 or e-mail [email protected]

In the 1955 version of It Came from Beneath the Sea, the giant octopus invader manages to destroy the Golden Gate Bridge, the Ferry Building, and Market Street before scientists can stop it. Join an Undaria removal party to make sure we have a happier ending to our current marine invasion!