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Hypnea musciformis is a highly opportunistic invader
well known for its large floating blooms in coastal Maui. Large biomass
washes up on the beaches of O‘ahu and Maui. This alga is easily identified
by the flattened, broad hooks at the end of many branches.
Hypnea musciformis in Hawaiian Islands.
Map by Jen Smith.
Hypnea musciformis beds with Ulva
fasciata at Maalea, Maui.
Clumps or masses of loosely intertwined, cylindrical
branches, 10 - 20 cm tall, 0.5 - 1.0 cm diameter, that become progressively
more slender towards tips. Firm, cartilaginous, highly branched. Branching
is variable and irregular, often tendril-like and twisted around axes of
other algae. The ends of many axes and branches are flattened with broad
hooks. Holdfasts are small, inconspicuous, or lacking. Usually red,
but can be yellowish brown in high light environments or nutrient poor
Easily distinguished from other native Hypnea spp. by
the presence of flattened, broad hooks at the tips of the branches (see
arrow on above figure). Often found as an epiphyte on reef algae such
as Sargassum echinocarpum, Sargassum polyphyllum, and Acanthophora
Medulla appear parenchymatous around central axial cell;
cortical filaments with few divisions on radii, outer layer pigmented.
Tetrasporangia zonately divided, in raised nemathecia, usually on ultimate
branches; spermatangia borne in chains in slightly swollen nemathecia at
base of branchlets. Cystocarps conspicuous, rounded, without discharge pore.
Hypnea musciformis is common on calm intertidal and
shallow subtidal reef flats, tidepools and on rocky intertidal benches. Most
often found low intertidal to shallow subtidal reef flats, attached to sandy
flat rocks, or frequently epiphytic on Sargassum and other algae. In
bloom stage, may be found free-floating.
Hawai‘i: O‘ahu, Moloka‘i, and Maui.
Mechanism of Introduction:
Introduced to Kane‘ohe Bay in 1974 for commercial
Philippines, Indian Ocean, Caribbean to Uruguay.
Hypnea musciformis is an extremely abundant alga that is
commercially cultivated throughout its world distribution as a food source
and for its kappa carrageenan. This alga was purposefully introduced to
Kane‘ohe Bay in 1974 from Florida for mariculture. This introduced invasive
spread quickly, reaching other islands by 1982. The success of this alga in
Hawai‘i is likely due to a rapid growth rate, ability to epiphytize other
algae and easy fragmentation. Drifting fragments reattach to other algae,
especially Sargassum, which can become detached during storms and
float long distances, carrying the epiphytic H. musciformis with it.
Dispersal may well have been enhanced via interisland travel with fouled
H. musciformis is often found in large, nearly unialgal
mats, and during the winter can represent 2/3 of the biomass of drift algae
on windward and leeward beaches on Maui. These mats are tossed ashore in
windrows up to 1.5 feet and are considered an odiferous pest. In peak
blooms, thousands of pounds wash up on Maui beaches.
Soon after its introduction, it was identified as a food
source for the green sea turtle, Chelonia mydas. H. musciformis
can make up a significant part the their diet, sometimes representing
99-100 percent of the seaweed mass found in their stomachs, but the actual
nutritional value has not been determined.
Abbott, I.A., 1999. Marine Red Algae of the Hawaiian
Islands. Bishop Museum Press, Honolulu, Hawai‘i.
Littler, D.S. and Mark M., 2000. Caribbean Reef Plants.
OffShore Graphics, Washington, D.C.
Russell, D.J., 1992. The ecological invasion of Hawaiian
reefs by two marine red algae, Acanthophora spicifera (Vahl) Bøerg.
and Hypnea musciformis (Wulfen) J.Ag., and their association with
two native species, Laurencia nidifica J.Ag. and Hypnea
cervicornis J.Ag. ICES Mar. Sci. Symp., 194: 110-125.
Russell, D. J. and G. H. Balazs, 1994. Colonization by the
alien marine alga Hypnea musciformis (Wulfen) J. Ag. (Rhodophyta:
Gigartinales) in the Hawaiian Islands and its utilization by the green
turtle, Chelonia mydas. Aquatic Biology. 47:53-60.
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.
Schneider, D.W, and R.B. Searles, 1991. Seaweeds of the
Southeastern United States. Duke University Press, London, England.
Ecological Success of Alien/Invasive Algae in Hawai‘i:
Marine Invasives in Hawai‘i: