Generally stowing away on boats, the invasive Undaria pinnatifida can spread rapidly. Also known as the edible seaweed wakame, Undaria has been found on the northern coast of West Anacapa Island where the waters are colder — its favorite environment — and National Park rangers ask the boating public to check lines, fishing gear, hulls, and areas less affected by high water movement before departing for the Channel Islands.
The brown seaweed was first seen at Anacapa in June 2016, and it has since populated the island’s entire northern coast. Seen on the West Coast at Long Beach in 2000, by 2007 it had spread to Ventura Harbor. A quick growth pattern and large size make Undaria a natural to compete with native seaweeds for territory and light, with unknown impacts to the ecosystem.
If Undaria is spotted, the park naturalists advise removing it by the roots and throwing it into the trash. If released back into the ocean, the plant’s microscopic spores can remain dormant for up to two years.
For those who wish to learn more about seaweeds, Lindsay Marks, a PhD candidate at UC Santa Barbara, will talk about the invasive Sargassum horneri which has floated far and wide. Her research includes the weed’s relationship to natives and a citizen’s monitoring website. The talk takes place on Thursday, May 11, at 7 p.m., at Ventura’s National Park HQ at 1901 Spinnaker Drive.