Kappaphycus Algae

Image Credit: eorhawaii.org

Image Credit: eorhawaii.org

Kappaphycus sp. (K. alvarezii, and K. striatum)

Hawaii Pacific Weed Risk Assessment: None

Regulatory Status: None

Prevention and Control Category: None


  • Two similar species of seaweed, both with thick, spiny branches (up to 2 cm in diameter) that can be green, yellow-orange, or red depending on the sunlight.

  • Grows in thick mats or clumps on reef flats or reef edges up to 20 meters depth

  • Native to the Philippines, introduced to Kaneohe Bay and Honolulu Harbor in the mid-1970’s for aquaculture research into potential use of chemical component (carrageenan)


  • Has a high growth rate. Can double in size in 15-30 days

  • Spreads mainly by fragmentation (pieces of seaweed float to new locations)

  • Can overgrow and kill coral by smothering, shading it from sunlight and abrasion

  • Grows faster than native seaweeds and coral

  • Causes shifts from diverse coral reef to a seaweed-dominated, low-diversity reef

  • Changes the bottom structure of the reef, reduces access to crevices and holes

  • Habitat loss may impact commercial and recreational fisheries


  • Oahu: Currently found only on the Windward Side of Oahu, in Kaneohe Bay

  • Kauai, Maui, Molokai, Lanai, Kahoolawe, Big Island: Not known to be present

Additional Information