Sargassum horneri, also called devil weed, was found at the Monterey Breakwater jetty in June 2020.
Sargassum horneri is a large, annual brown seaweed, native from Japan to the Philippines. In 2003, the alga invaded Long Beach Harbor and rapidly spread upcoast to the Channel Islands and downcoast to Todos Santos, Mexico. It grows on rocky reefs in the same habitat as giant kelp and other brown algae and is most common between 5 – 20 m. This is one of three species of Sargassum that have become persistent in California. To learn more about this species and its detection in Monterey Bay, read the PDF below.
