Two Types Of Non-Native, Invasive Seaweed Prompt Concern For Marine Protected Areas Off South Coast

May 2, 2017

There’s an undersea invasion taking place right off our coastline.

Two types of non-native seaweed are spreading along the California Coast, and are creating special concern for Marine Protected Area and Channel Islands National Park.

An outbreak of one type of seaweed has been spreading rapidly near Anacapa Island since being discovered about a year ago.

David Kushner is a Marine Biologist with Channel Islands National Park. Kushner says if you like sushi, you’ve probably tasted Undaria Pinnatifida. But, the seaweed which is common in Asia can be disruptive to other, native seaweeds. It’s believed that it spreads as a hitchhiker, being dragged by boats, or attaching itself to hulls.

One it gets into a harbor, it can be spread from boat to boat. Kushner says trying to eradicate it isn’t practical. He says the way people can help is to remove it from the hulls of their boats. It should be taken out of the water, and thrown away so the spores don’t spread.

The marine biologist says there’s also a second type of non-native seaweed creating concern off our coastline, called Sargassum horneri. Lindsay Marks is a UC Santa Barbara researcher who’s been trying to track the spread of Sargassum off our coastline.  Unlike Undaria, Sargassum has air bladders which allow it to easily float in currents, and spread. Efforts to control it also appear to be impractical.

Marks says they are turning to the public for help in trying to learn more these invasive seaweeds. There’s a website where people can report their seaweed sightings, called

Marks will speak about the seaweed invasion in a May 11th public lecture at the Channel Islands National Park Visitor Center, at Ventura Harbor. The 7 p.m. event is free, and open to the public.