Learn & Explore/Species/Introduced & Invasive/Smothering Seaweed
Smothering Seaweed
Category: Invasive
A fast‑spreading red seaweed that forms thick mats on reefs — smothering corals, blocking light, and altering habitat.
Smothering Seaweed
(Eucheuma spp.)
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Thick intertwined branches that form mats 1
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Branches are cylindrical axes with spines 1
Habitat
Typically found in shallow, subtidal reef flats 2
Impacts & Concern
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High growth rate and reproduces through fragmentation 2
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Shades out and smothers corals 2
Introduction
Introduced from the Philippines to Kāne‘ohe Bay in 1974 for scientific experiments 2
Distribution in Hawai‘i
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Kauaʻi: Not documented
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O‘ahu: Present in Kāne‘ohe Bay
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Molokaʻi: Not documented
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Lānaʻi: Not documented
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Maui: Not documented
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Hawaiʻi Island: Not documented
Related AIS Team Management Projects
Urchin outplanting efforts in Kāne‘ohe Bay
References
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CABI. (2019). Eucheuma Spp. [Data sheet]. https://www.cabi.org/isc/datasheet/102037
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Russell, D. (1983). Ecology of the Imported Red Seaweed Eucheuma striatum Schmitz on Coconut Island, Oahu, Hawaiʻi. Pacific Science, 37(2), 87-107. https://core.ac.uk/download/pdf/5093462.pdf
Smothering Seaweed (Kappaphycus alvarezii)
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Coarse branches in irregular patterns 1
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Shiny green to orange-yellow in color 1
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Intertwined branches to form thick mats 1
Habitat
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Typically found on patch reefs in shallow water 2
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Inhabits sand-covered grooves in reef 2
Impacts & Concern
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High growth rate and vegetative regeneration makes it quick to spread 1
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Can double in size in 15-30 days 1
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Shadows and smothers native corals 1
Introduction
Introduced to Kāne‘ohe Bay for commercial cultivation in 1974 1
Distribution in Hawai‘i
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Kauaʻi: Not documented
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O‘ahu: Present in Kāne‘ohe Bay
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Molokaʻi: Not documented
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Lānaʻi: Not documented
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Maui: Not documented
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Hawaiʻi Island: Not documented
References
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UH Mānoa. (2001). Kappaphycus alvarezii Fact Sheet. https://www.hawaii.edu/reefalgae/invasive_algae/pdf%20files/kappaphycus_alvarezii.pdf
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Rogers, S.K. & Cox, E.F. (1999). Rate of spread of introduced rhodophytes Kappaphycus alvarezii, Kappaphycus striatum, and Gracilaria salicornia and their current distributions in Kane’ohe Bay, O’ahu, Hawai’i. Pac Sci, 53(3), 232-241.
