Invasive Seaweeds and Hull Fouling Species

Devil Weed

• Scientific Name

  Sargassum horneri - Visit algaeBASE for full scientific classification. 

• Description

  

  Sargassum horneri. © 2009 Jessie Altstatt.

   

  • Annual brown algae, up to about 15 feet long.
  • Small, fern-like leaf blades on wiry "stems" with many small air bladders.
  • Forms very dense groves.
• Habitat

  • Occurs in the intertidal zone and down to depths of 100 feet.
• Invasion Pathways and Distribution

  • Native to warm seas in Japan and Korea.
  • Extensive natural dispersal capabilities via drifting fragments.
  • Can spread by attaching to vessel hulls or by drifting.
  • Invasive in Baja California, Mexico, southern California, and the California Channel Islands.
  • First reported in California in 2003.
• Life History

  • Capable of self-fertilization.
  • Young plants grow from embryos released from numerous, conspicuous, chili pepper-shaped reproductive structures.
  • Completes its life cycle in approximately one year.
• Impacts

  • Spreads quickly.
  • Areas in southern California currently dominated by this species that thrives in warm water conditions.
  • Competes with natives for space and light.
• References and Useful Links

  For references by category and links to other useful AIS sites see our LEARN MORE page.