Please watch for this invasive seaweed!

The non-native brown seaweed Sargassum filicinum was initially discovered in Long Beach Harbor in 2003, then Kathy Ann Miller and Channel Island Research Program divers found it in a few locations at Santa Catalina Island last spring. 

    Already this invasive seaweed appears to be spreading rapidly. This fall we observed it to be much more abundant at the initial Catalina location and found it in patches at most other sites we dove, including Bird Rock, Isthmus Reef, Pumpernickel Cove and Big Geiger Cove in the Isthmus area, as well as miles away to the east at Hen Rock (east of Long Point). In September, Constance Gramlich's keen eye found it at Point Loma, San Diego - the first known mainland outer coast location!
   

 Sargassum filicinum has an annual life cycle. It was reproductive last spring at Catalina, with some plants deteriorating (see poster). No reproductive plants were found this fall. Instead, fresh-looking young plants ranged from tiny recruits to bushy 75 cm tall individuals buoyed up by gas bladders (see larger photos). They appear yellowish-brown and very fern-like, with characteristic oval gas bladders, notched blade margins, and tiny spines on the supporting axes.   

To document its spread and understand its ecological impact, we would greatly appreciate additional records of its occurrence (photos or specimens). Please contact Kathy Ann Miller ( This email address is being protected from spam bots, you need Javascript enabled to view it ) and myself ( This email address is being protected from spam bots, you need Javascript enabled to view it ) if you find it or would like further information.
       Thanks,
                   Jack Engle 

The paper describing these initial findings is out in electronic form pending its publication in Biological Invasions (http://dx.doi.org/10.1007/s10530-006-9060-2) Miller, K.A., J.M. Engle, S. Uwai, and H. Kawai. First report of the Asian seaweed Sargassum filicinum Harvey (Fucales) in California, USA. Biological Invasions.

Abstract:  We report the occurrence of the brown seaweed Sargassum filicinum Harvey in southern California. Sargassum filicinum is native to Japan and Korea. It is monoecious, a trait that increases its chance of establishment. In October 2003, Sargassum filicinum was collected in Long Beach Harbor. In April 2006, we discovered three populations of this species on the leeward west end of Santa Catalina Island. Many of the individuals were large, reproductive and senescent; a few were small, young but precociously reproductive. We compared the sequences of the mitochondrial cox3 gene for 6 individuals from the 3 sites at Catalina with 3 samples from 3 sites in the Seto Inland Sea, Japan region. The 9 sequences (469 bp in length) were identical. Sargassum filicinum may have been introduced through shipping to Long Beach; it may have spread to Catalina via pleasure boats from the mainland.

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Jack Engle, Ph.D.

Associate Research Biologist

Marine Science Institute

Santa Barbara, CA 93106-6150

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Phone: 805.893.8547   Fax:   805.893.8547