Hawaiian seaweeds profile

Education Department
Waikïkï Aquarium
University of Hawai‘i-Mänoa
MARINE LIFE PROFILE:
SEAWEEDS or LIMU
Seaweeds, called limu in Hawaiian, include a wide variety of multicellular marine algae.
These marine plants are the basis of the food web on reefs and rocky shores. Through the
process of photosynthesis, they use light energy and raw materials, like carbon dioxide and
water, to build energy-rich chemicals, like sugars and starches. Plants use these high-energy
chemicals to support their own survival and growth, and many marine animals eat seaweeds to
obtain the energy and raw materials they need. Plants are producers (making their own food)
and animals are consumers (depending upon the plants or on other animals for food).
In Hawai‘i, limu are found in many marine environments from tidepools to deep reef
slopes. Some are found as deep as 600 feet (180 m), but all must live where some sunlight can
reach them. Most seaweeds also need a hard surface of rock or coral on which to grow, few are
found in sandy environments. There are about 600 different species of seaweeds in Hawai‘i.
The factors that affect their growth, like the kind of seafloor, amount of water movement,
amount of light, and kinds of grazing animals, are different for each species and determine the
habitat and season in which each will thrive.
Seaweeds are split into three basic groups based on the color of the pigments they have
for photosynthesis. Green seaweeds have grass green pigments called chlorophyll, brown
seaweeds are golden or brownish-green because they have brown and orange pigments in
addition to the green ones. Red seaweeds are usually pinkish or purplish in color, reflecting their
additional reddish and bluish pigments. Algae are often classified as members of the Kingdom
Protista; other classification systems place them within the Kingdom Plantae.
Another group, sometimes called the blue-green algae, are actually more closely related
to bacteria than they are to other seaweeds. While they look like algae, their primitive cell
structure places in the Kingdom Monera. Called Cyanobacteria, they can be bluish, purplish, or
even black as a result of their particular reddish and bluish pigments. Blue-greens are common
in tropical waters.
Seaweeds are different from land plants in many ways. Since they can absorb nutrients
from the water all around them, they do not need roots to draw water and minerals from the soil.
Instead, seaweeds have a holdfast, a disc-shaped or branched structure that anchors them firmly
to the bottom. The body of a seaweed is made up of one or more blades instead of leaves.
Blades come in many different shapes, depending upon the seaweed species: flat and leafshaped,
highly branched, even spherical. The blades are the main sites for photosynthesis.
Sunlight and nutrients are absorbed right across their surfaces. The blades may be attached to a
stipe, a stem-like structure that helps hold the blades up off the seafloor. The stipe is flexible
and bends easily with the waves and currents. It doesn't have to be heavy and woody like the
stems or trunks of land plants because the water helps support the plant.
While many seaweeds are soft and flexible, some are quite hard because their cells
contain chalky deposits of calcium carbonate. These stony deposits may help the seaweed
survive the drying effects of low tides, withstand the pounding surf, or even discourage the
feeding activities of seaweed grazers. These hardened seaweeds, called calcareous or coralline

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algae, are very important in building Hawaii's reefs - they are like cement growing between the
corals, adding strength to the reef structure; they can even thrive in habitats where wave impact
would break corals.
Limu were very important to early Hawaiians. More than 70 different kinds were used;
eaten fresh, blended with other foods, used as spices, used as medicines, and even used in special
religious ceremonies. Today, many Hawaiian residents still harvest fresh limu for food or buy it
at the market. Worldwide, seaweed products are used to thicken and smooth many foods and
milk-products, as well as toothpaste, beauty creams, paints, and medical products like bacterial
culture plates, time-release pills, and dental impression gels.
Classification:
Kingdom Monera Kingdom Protista
Phylum Cyanobacteria (blue-green algae) Phylum Clorophyta (green seaweeds)
Phylum Phaeophyta (brown seaweeds)
Phylum Rhodophyta (red seaweeds)
Examples of Hawaiian Seaweeds, by Habitat
High intertidal, beach or tidepool area
Ahnfeltia cocinna, limu ‘aki‘aki
Sphacelaria furcigera
Ulva fasciata, limu pälahalaha, sea lettuce
Enteromorpha sp., limu ‘ele ‘ele
Padina japonica
Reef flat
Acanthophora spicifera, introduced species (l950’s)
Codium spp, limu wawae‘iole, limu a‘ala‘ula, rat’s food sea weed
Caulerpa spp.
Dictoyosphearia cavernosa, bubble alga
Dictyota spp., limu alani
Eucheuma striatum, introduced species (1970’s)
Sargassum spp., limu kala
Gracilaria spp., limu manauea, ogo
Laurencia spp., limu mäneoneo, limu liep‘epe‘e
Hypnea musiformis, introduced species
Lyngbya majuscula, swimmer’s itch seaweed
Reef crest
Asparagopsis taxiformis, limu kohu
Porolithon spp., encrusting calcareous red algae
Pterocladia capillacea
Subtidal
Halymenia formosa, limu lepe‘ahina, red sea lettuce
Dictyopteris spp., limu lipoa
Halimeda opunti
SELECTED HAWAIIAN SEAWEEDS (LIMU)
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BROWN SEAWEEDS
Sargassum
Brown ear seaweed limu kala
Padina sp. Sargassum echinocarpum
©Waikïkï Aquarium
©Waikïkï Aquarium
RED SEAWEEDS GREEN SEAWEEDS
Encrusting red coralline algae Reticulated sea lettuce
Porolithon sp. Ulva reticulata
SELECTED GREEN ©Waikïkï SEAWEEDS Aquarium OF HAWAI‘I
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Chalky green disc algae
Halimeda opuntia
Reticulated sea lettuce
Ulva reticulata
© Waikïkï Aquarium
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© Waikïkï Aquarium

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© Waikïkï Aquarium
SELECTED RED SEAWEEDS OF HAWAI‘I
Encrusting Red Coralline Algae
Porolithon sp.
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Brown ear seaweed or
limu pepeiao
Padina spp.
© Waikïkï Aquarium
SELECTED BROWN SEAWEEDS OF HAWAI‘I
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Sargassum
limu kala
Sargassum echinocarpum
© Waikïkï Aquarium