University of Hawai‘i ♦ Botany Department

Invasive Marine Algae of Hawai‘i

Invasive Algae Home            Red Algae            Green Algae             Brown Algae               Seagrasses             Glossary            


Halophila decipiens





Class Order Family
Anthophyta Alismatidae Hydrocharitales Hydrocharitaceae

       Click on pictures for larger images



Halophila decipiens, a pantropical species, was recently discovered in both shallow and deep sandy areas on Hawaiian coasts. It may compete with the native seagrass.



Flower on Halophila decipiens.




Halophila decipiens bed, O‘ahu.




Pairs of leaves on petioles formed along a rhizome rooted in sand. Leaves from 3 - 8 mm wide, obovate, not narrowing at base, thin and hairy; margin spinulose. Petiole 3 - 15 mm long. Male and female flowers are produced at each leaf node. Branching leads to intertwined plants in a meadow or runners colonizing new substrate.


Structural Features

Leaf blade thin and flaccid out of water; fine hairs on both sides of leaf make leaf feel rough. Spines on margin visible with magnification. Ripening fruit often conspicuous on rhizome.



Forms dense meadows in sand rich in organic matter. Found at depths from 0.5 - 35 m. Often coated with epiphytes.



Hawai‘i:  O‘ahu, Hawai‘i.

Mechanism of Introduction:  Unknown.

Worldwide:  Subtropical to tropical Pacific, Indian, Atlantic Ocean, Caribbean.



Halophila decipiens was discovered October, 2000 near the Kahala Mandarin Hotel and several additional populations have since been located. If it is found to out-compete the native Halophila hawaiiana, then it may pose a threat to that species due to its great reproductive capacity. Research is underway to determine what impact this species may have on the native seagrass and associated communities.


Phillips, R.C. and E.G. Menez. Seagrasses. 1988. Smithsonian Contributions to the Marine Sciences 34. 89 pp.

E.G. Menez and R.C. Phillips. 1983. Seagrasses from the Phillipines. Smithsonian Contributions to the Marine Sciences 21. 40 pp.


 Web Pages

Seagrass Page.




Site maintained by Department of Botany, Unversity of Hawai‘i at Manoa

Site supported the Bishop Museum, National Marine Fisheries Service,  Packard Foundation, and US Fish and Wildlife Service

Website by Linda Preskitt © 2002   (