University of Hawai`i

Botany Department

          Marine Algae of Hawai`i

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Bryopsis pennata

J.V.Lamouroux 1809

Invasive Native



Class Order Family
Chlorophyta Chlorophyceae Bryopsidales Bryopsidaceae

Click on pictures for larger images




Bryopsis pennata is a small feather alga
often found in the reef flat community. The opportunistic green alga has the potential to become invasive with supportive
environmental conditions.














Clumps of feathery  Bryopsis pennata surrounded by other
red and  green algae.



Thallus filamentous, bushy, in tuft-like mats, to 10 cm high. Fronds feather-like, 8 - 15 mm wide, pinnately branched; lateral branches of uniform length, constricted at base where joined to main axes. Branchlets in two opposite rows on upper half of branch, lower half of branch is bare. Rhizoidal system is fibrous, tightly interwoven.  Color is glossy dark green, often with light blue iridescence.


Structural Features

Main axes 240-360 µm diam; lateral branchlets 75-150 µm diameter. Vegetative pennae function as the gametangia. Plants are dioecious, with male plants becoming yellowish-green and female plants turning dark green.



Broypsis pennata forms soft, feathery clumps attached to basalt rocks and rubble on shallow reef flats, in tidepools, and in lower intertidal habitats of coastlines with low wave action.



Hawai‘i:  Northwest Hawaiian Islands, O‘ahu, Maui, Kaua‘i, Lana‘i, Moloka‘i and Hawai‘i Island.

Mechanism of Introduction:  Indigenous to Hawai‘i.

World-wide Distribution: Australia, Atlantic Ocean, Mediterranean, Caribbean, Indian and Pacific Oceans.



Bryopsis pennata is usually only a small part of the biomass of the diverse, highly competitive reef flat community. Soft, feathery clumps of this alga are often found attached to rocks among species of turfs and other low growing macroalgae. Like most green algae, Bryopsis species are highly opportunistic in eutrophic conditions.  Communities will have a higher biomass of this fast growing green alga are when located near fresh water output that is nutrient rich, or where water temperatures fluctuate.


Bryopsis species are potentially invasive. Like the troublesome Caulerpa taxifolia, the genus produces chemical defenses that are toxic to most herbivorous organisms and easily reproduces vegetatively from the smallest fragments. Therefore, if environmental conditions occur that support fast growth of this species, it may become more competitive and possibly dominant.


Bryopsis pennata is a well-known pest alga species in commercial aquariums and the aquarium trade. Often referred to as Sea Ferns, the soft feathery alga are usually introduced to aquariums on live rock. The nutrient rich water in aquariums provide the perfect habitat for the fast growth of B. pennata, and control in the aquarium habitat is a constant challenge. The unchecked growth that occurs in the nutrient rich water of an aquarium with no predators can easily be expected under similar conditions on our reefs.


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.

Russell, D. J. and G. H. Balazs, 2000. Identification manual for dietary vegetation of the Hawaiian green turtle, Chelonia mydas. NOAA TM-NMFS-SWFSC-294. 49 pp.


Web Pages

Virtual Herbarium.



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