University of Hawai`i

Botany Department

          Marine Algae of Hawai`i

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Enteromorpha flexuosa

(Wulfen) J. Agardh 1883

Invasive Native



Class Order Family
Chlorophyta Chlorophyceae Ulvales Ulvaceae

Click on pictures for larger images




Enteromorpha flexuosa is a native green
alga that exhibits invasive characteristics in areas of fresh water intrusion and high nutrient input.

















Enteromorpha flexuosa is tide pool, O‘ahu.




Long, filamentous green alga up to 15 cm tall, mostly tubular, hollow, with tube walls 1 cell thick, axes 1-7 mm wide. Branches cylindrical throughout or with the terminal portion expanded and bladelike, or centrally compressed with only the margins hollow. Larger tubular portions may or may not branch; if branched, with narrow filamentous branchlets. Attached to rocky substrate by rhizoids that grow from basal cells of the tube. Grass green.


It often grows in tufts of 6 cm long, but in areas of high nutrients and fresh water, can form long, hairlike strands up to 20 cm long.


Structural Features

Thallus hollow tube, walls 1 cell thick. Cells in surface view arranged in short longitudinal rows. Cells rounded rectangular, 10-28 µm wide, 8-30 µm long, in somewhat longitudinal and often transverse rows; basal cells up to 50 µm long.



Forms clusters or tufts attached to rocks in sandy areas, high intertidal to mid-intertidal. Will often be exposed at low tide, and often found near freshwater intrusion. Epiphytic in ponds.



Hawai‘i:  Kaua‘i, O‘ahu, Maui, and Hawai‘i Island.

Mechanism of Introduction:  Indigenous to Hawai‘i.

Worldwide:  Worldwide distribution in both temperate and tropical waters of the Pacific and Atlantic Ocean, Indonesia, Philippines, southern Japan, Viet Nam, and Thailand.



Enteromorpha flexuosa is a very common high intertidal green alga found wherever there is freshwater intrusion, such as freshwater stream or underwater spring input to the ocean. It is often associated with coastal areas of high nutrients, including areas with residential and industrial development.


E. flexuosa is considered an invasive and fouling species in much of the world. This is an opportunistic species that has a very successful reproductive stage. Under the right conditions it will release propagules daily. The motile reproductive cells actually have the ability to photosynthesis, thus increasing their potential viability and dispersion.


Because of this high reproductive ability, E. flexuosa is markedly fecund and, therefore, an excellent pioneer species, settling available substrates quickly. But it does not compete well with other successional species. In studies of disturbance and settlement, E. flexuosa was found to maintain a low percent cover in undisturbed areas but, following a disturbance, density increased dramatically.


E. flexuosa is often found in communities with or near Ulva fasciata, another pioneer green alga species. Both are fouling organisms associated with industrial pollution. Anti-fouling studies investigating control and/or eradication of fouling species identify these two species as serious pests in shipping and industrial areas.


Abbott, I.A., 1996. Limu: An ethnobotanical study of some Hawaiian seaweeds. National Tropical Botanical Garden, Lawai, Kaua‘i, Hawai‘i.4th edition.

Beach, K.S., C.M. Smith, T. Michael, and H.W. Shin, 1995. Photosynthesis in reproductive unicells of Ulva fasciata and Enteromorpha flexuosa: implications for ecological success. Mar. Ecol. Prog. Series, 125: 229-237.

Littler, D.S. and Mark M., 2000. Caribbean Reef Plants. OffShore Graphics, Washington, D.C.

Magruder, W.H., and J.W. Hunt, 1979. Seaweeds of Hawai‘i. Oriental Publ. Co., Honolulu, Hawai‘i.

 Web Pages

Hawaiian Reef Algae.

The Indian River Lagoon Species Inventory;

Virtual Herbarium.


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