General Impact
Kappaphycus spp. high growth rate, plastic morphology, and extremely successful vegetative regeneration makes them potentially destructive invasive species not just in Hawai‘i but around the globe (University of Hawai‘i, UNDATED). Conklin et al. (UNDATED) reports that Kappaphycus spp. is a serious danger to the coral reefs. Research has shown that Kappaphycus spp. have the ability to overgrow and kill coral. Woo et al. (1999) states that, "Observations have shown that the alga is able to coalesce into the tissue of the coral, providing a strong means for attachment, and thus allowing the alga to persist in high wave energy environments. The novel substrate and structure the algae provides may permit settlement of epiphytes previously absent, as well as shelter and protection for mesograzers." Woo (2001) documented fragments of Kappaphycus spp. weighing 0.05 g that were capable of net growth in the field, suggesting that fragments created by physical disturbance can be carried by waves and currents to new locations where they can possibly establish.
Location Specific Impacts:Kurusadai Is. (India) 
Reduction in native biodiversity: The Gulf of Mannar is rich in diversity of corals, especially in three genera, viz. Acropora, Montipora and Porites. Acropora is the most diverse genus with 24 species of branching corals. A bleaching event during 1998 destroyed most (75%) of the live coral cover especially branching corals belonging to the genera Acropora and Pocillopora. Chandrasekar et al. (2008) conclude from the results of their study that Kappaphycus alvarezii which has established on the branching corals are destroying them through shadowing and smothering impact of the infestations. Gulf of Mannar Biosphere Reserve (India)
Reduction in native biodiversity: The Gulf of Mannar is rich in diversity of corals, especially in three genera, viz. Acropora, Montipora and Porites. Acropora is the most diverse genus with 24 species of branching corals. A bleaching event during 1998 destroyed most (75%) of the live coral cover especially branching corals belonging to the genera Acropora and Pocillopora. Chandrasekar et al. (2008) conclude from the results of their study that Kappaphycus alvarezii which has established on the branching corals are destroying them through shadowing and smothering impact of the infestations. Kane'ohe Bay (United States (USA))
Competition: The smothering and subsequent weakening of the reef structure at Kan'eohe Bay, Hawai'i by the introduced Kappaphycus striatum (Smith pers. comm.) is of a grave concern as this alga (and other related Kappaphycus species) has been introduced to most Pacific Islands for cultivation (Coles et al. 2003).
Economic/Livelihoods: The intentionally introduced Philippine seaweed (K. alvarezii and K. striatum) covers large areas of Kane‘oheohe Bay coral reefs, reducing potential tourist value (Carlton, 2001).
Habitat alteration: K. alvarezii presents a serious danger to the reefs within the bay. Permanent photoquadrats have established the ability of this alga to overgrow and kill corals, while benthic surveys have shown that the alga has already overgrown >50% of the reef substrate in some areas (Conklin et al. UNDATED).
Modification of natural benthic communities: Evidence suggests that Kappaphycus spp. has significantly altered benthic community structure and species diversity in Kane‘ohe'ohe Bay (Smith, UNDATED). Waikiki (United States (USA))
Competition: Two mat-forming red algae (Gracilaria salicornia and K. alvarezii), introduced to Waikiki and Kane‘ohe'ohe Bay for experimental aquaculture in the 1970's, appear to be causing reductions in diversity and coral death (Smith et al. 2003). Venezuela
Ecosystem change: Two exotic species of marine red algae: Euchema denticulatum and K. alvarezzi, which have proved to be invasive, has been the introduction of the Venezuelan government. These species reproduce asexually by fragmentation and produce allelopathic substances that are potentially dangerous to coral ecosystems (Barrios, 1999). These introductions were made without studies of any kind, and Servicio Autónomo de los Recursos Pesqueros y Acuícolas (Autonomous Service of the Aquaculture and Fisheries Resources) (SARPA) approved them after the algae were already in Venezuelan waters (Pérez et al. 2003).
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