Kappaphycus Algae

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



  • 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

In Hawaii:

  • 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

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