Hawai'i Coral Reef Network

Plants of Hawai'i

Kingdom Monera

Division Cyanophyta (cyanobacteria or blue-green algae)

Lyngbya majuscula

Description: filamentous seaweed black to dark gray but can be shades or red green or yellow. 5-10cm long may cause swimmers itch, found with other seaweeds.

Habitat: shallow tide pools and subtidal habitats.

Kingdom Plantae

Division Chlorophyta (green algae)

Order Ulvales

Ulva fasciata

Description: very common known as sea lettuce flat twisted blade 1-10cm wide and 5-100 cm long. grass green in color.

Habitat: abundant in high nutrient water, intertidal rocks and pools. Very common

Ulva reticulata

Description: green grass color, looks like netting, up to 3m in length.

Habitat: reef flats, and covering other seaweeds.

Order Bryopsidales

Bryopsis plumosa

Description: delicate soft featherlike appearance, dark green color make this easily recognized.

Habitat: shallow reef flats, and tidepools, and lower intertidal habitats with low wave action. 2-12 cm long.

Codium arabicum

Description: a dark green spongy mass, 0.5-3cm thick and up to 15cm wide. characterized by rolling bumps or convolutions on surface.

Habitat: intertidal and reef flats.

Codium edule

Description: forms spongy mat-like mass of many intertwined dark green cylindrical branches. 3-8cm in diameter. Branches attach whatever they contact.

Habitat: reef flats, in lower intertidal habitats and in tide pools. Looks like green rat's feet.

Codium reediae

Description: dark green with flattened branches, 1-2cm wide attached to bottom in one place, upright.

Habitat: in fairly calm water such as deep tide pools and on deep reef flats growing to 10cm in length.

Order Dasycladales

Neomeris annulata

Description: very distinct, fingerlike form grows 4cm high, found in tide pools and reef flats, and in subtidal habitats.

Habitat: depressions of rocks. Top is green and fuzzy and bottom is calcified and white.

Order Caulerpales

Caulerpa taxifolia

Description: featherlike branches green in color 3-15cm tall. found in sandy areas of tide pools, and reef flats. Appears like Caulerpa sertularioides except branches are flat with angled edges giving a square or rectangular appearance.


Caulerpa racemosa

Description: looks like small bunches of grapes, light green in color. and up to 4cm thick and horizontal runner which anchors the "grapes" to the substrate.


Halimeda discoidea

Description: dark green outer segments; may have a calcified and whitish center. able to anchor in sand as well as on rock.

Habitat: found in deeper waters. Dead bits of this alga makes up a large portion of Hawaii's beach sand.

Halimeda opuntia

Description: calcareous green to whitish seaweed found in deeper water between rocks in bunches. Segmented usually with midribs. 0.5-2cm wide segments, with lengths of 30 cm.


Order Siphonocladales

Dictyosphaeria cavernosa

Description: commonly known as the "Green Bubble Alga" due to the large round cells. When small the thallus is a hollow sphere, when larger the sphere may burst becoming convoluted and cup shaped. The seaweed is grass green in color and can form extensive mats over the reefs surface 1-10cm thick.


Dictyosphaeria versluysii

Description: like D. cavernosa, also has bubble like cells, but is completely solid in middle and always remains rounded. Grass green in color, but sometimes bluish in color. 1-2 cm high and 1-5 cm wide.


Microdictyon japonicum

Description: M. japonicum is a single flattened blade consisting of a meshwork of fine connecting branches. It is grass-green in color, from 1 to 6cm wide and 1 to 4 cm high.

Habitat: low intertidal areas of rocky coastlines, on flat reefs, and in between the branches of corals at deeper depths.

Division Phaeophyta (brown algae)

Order Dictyotales

Dictyoperis australis

Description: brown color with dark spots from 10-40 cm. flat blades 1-2cm wide with midrib. Produces strong odor.

Habitat: abundant deep water seaweed. found in dense beds at depths of 3-20 meter.

Dictyoperis plagiogramma

Description: similar to D. australis but smaller, 5-20 cm high and narrow blades, of 0.5 -1 cm wide. Brown with ruffled margins and a midrib.

Habitat: on rocky shores at about zero tide level and on reef flats. and outside reef crests in deeper water.

Dictyota acutiloba

Description: flat small twisted blades forming Y pattern and lacks midrib. size varies from 3-20cm and light brown in color.

Habitat: commonly found in tide pools and reef flats and deeper subtidal habitats.

Dictyota sandvicensis

Description: exhibits a yellow green iridescence. Blades of 2-5mm wide lack midribs, branches in a Y pattern. grows to 12cm high.

Habitat: in tide pools and on reef flats.

Lobophora variegata

Description: flat orange to dark brown seaweed 1-8cm across, grows over rocky substrate attached in only a few places. disk shaped.


Padina australis

Description: flat seaweed, with rolled edges, light brown in color and slightly calcified, blades may be split. Attached by single holdfast, 5-20cm tall.

Habitat: in deep tide pools and on reef flats.

Padina japonica

Description: flat blade rolled into a circle, upper surface is whitish, lower surface brownish. Tends to be smaller then P. australis, with blades not split.


Stypopodium hawaiiensis

Description: beautiful iridescent blue or green color. consists of many flat blades without the in-rolled margin as in the species Padina.

Habitat: on wave swept beaches and reef flats, brightly colored so is noticeable.

Order Fucales

Sargassum echinocarpum

Description: Golden to dark brown holly-leaf like blades with mid rib and flattened stems. size is 5-70cm tall with blades at 0.3-2cm wide.


Sargassum obtusifolium

Description: found in tide pools and reef flats. Brown leaf like blades with midrib, round smooth main stems and gas bladders on round smooth stalks. Size is 5-50cm tall and 0.3-2cm wide.


Sargassum polyphyllum

Description: Many brown blades with a midrib, and when present gas bladders with leaf like stalks. Stems show short spiny projections and grows 5-40cm tall with blades .5-1cm wide.

Habitat: found in wave swept benches, tide pools and on reef flats, and occasionally deeper depths.

Turbinaria ornata

Description: stiff erect seaweed with distinctive angular turban-like blades and a central stipe. Light brown color and grows 2-20cm tall.

Habitat: on rocky intertidal coastlines in tide pools and on reef flats and crests.

Order Scytosiphonales

Colpomenia sinuosa

Description: hollow saclike seaweed, golden brown in color and can have a smooth or convoluted surface. 1-5cm diameter, up to 20cm in diameter.

Habitat: found in several habitats.

Order Sphacelaiiales

Sphacelaria furcigera

Description: dark brown-black fuzzy tuft of filaments of all the same length. Up to 2cm tall.

Habitat: on rocky surfaces, or larger seaweeds in tide pools on reef flats.

Division Rhodophyta (red algae)

Order Nemaliales

Liagora sp.

Description: pink to red, and gooey at the ends of the tips.

Habitat: common on reef flats and tide pools but can be found in deeper waters.

Trichogloea requienii

Description: slippery round gooey branches. Branches 3-6mm in diameter and height varies from 5-40 cm. Light pink and slightly calcified seaweed.

Habitat: grows on reef flats and in deeper subtidal habitats to 10 m.

Galaxaura fastigiata

Description: this calcified seaweed is white to pink in color with stiff, hollow cylindrical branches and deep pits in the ends.

Habitat: found in tide pools and reef flats where it reaches a height of up to 15cm.

Galaxaura marginata

Description: looks like G. acuminata with hollow branches. Calcified seaweed is pink to red and grows to 15cm in length.

Habitat: found in deep tide pools or at deeper depths.

Order Bonnemaisoniales

Asparagopsis taxiformis

Description: red to bluish violet color. Fluffy appearance and shaped like a Christmas tree. grows 3-15cm high.

Habitat: in shallow subtidal habitats with heavy water motion.

Order Cryptonemiales

Grateloupia filicina

Description: this is a soft limp & slippery smooth seaweed with somewhat flattened branches that can be red green brown or almost black. Size and shape vary greatly from 0.5-5mm wide and 2-30cm long. with either few or many branches.

Habitat: at zero tide, rocky coastlines and shallow reef flats.

Gibsmithsia hawaiiensis

Description: many thick, lose branches forming from a central stipe. Color varies from red to white and size from 3-12 cm.

Habitat: most commonly found growing in between branches of corals in waters deeper than 5 m but can be found on reef flats occasionally.

Peyssonnelia rubra

Description: red to maroon encrusting seaweed calcified on its lower surface. Its edges are free but the bottom remains firmly attached to rubble, dead coral, or other hard surfaces.

Habitat: common in most subtidal habitats.

Portieria hornemanni

Description: produces a distinctive strong odor. Bright red to orange-red and grows 2-6cm high with branches that are rolled inward at the tips.

Habitat: found in almost any habitat.

Order Corallinales

Jania adherens

Description: calcified brittle branches less then 0.5mm and 0.3-2cm long. pink to white color.

Habitat: close examination of almost any habitat will reveal the presence of this seaweed

Porolithon gardineri

Description: forms pinkish calcareous crusts or much branched hemispherical shaped heads 10-30cm across (or larger).

Habitat: on reef crest & just seaward of crest.

Porolthon onkodes

Description: forms extensive pinkish to purplish chalky crusts in intertidal areas exposed to surf action. Due to strong tolerance to sunlight and desiccation and its crustose nature it is extremely successful in occupying high wave energy habitats. P. onkodes performs a critical role in the formation and maintenance of the biotic reefs of Hawaii by providing an actively growing reef rim, allowing consolidation and cementation of reef material to occur in protected shoreward areas or the Porolithon ridge.

Habitat: intertidal areas exposed to surf.

Order Gigartinales

Gracilaria coronopifolia

Description: solid cylindrical branches 1-4mm wide with short pointed tips. red in color but often bleaches to pink or white in bright sunlight. Grows 6-20cm tall. When reproductive "bumps" appear on the surface, it is illegal to collect reproductive Gracilaria coronopifolia.

Habitat: on reef flats, but occasionally found in tide pools.

Gracilaria salicornia

Description: cylindrical branches 2-5mm in diameter, usually distinctive constrictions. Forms mats 1-5cm thick. Bright yellow to orange-brown.

Habitat: in tide pools and reef flats.

Hypnea musciformis

Description: rounded main branches 1-3mm diameter with short pointed side branches. Length grows from 3-30cm. Bright yellow to dark red.

Habitat: in shaded areas.

Predaea weldii

Description: branches are fluorescent red soft and gooey. Reaches a length of 5 cm.

Habitat: in subtidal habitats between the branches of corals.

Order Ceramiales

Acanthophora spicifera

Description: 1-3mm solid cylindrical branches. Covered with many distinctive small spine-like branches. Grows to 3-20cm high. Red, brown or dark green in color but turns yellow in bright sunlight.

Habitat: abundant in calm shallow reef flats, tide pools and intertidal benches.

Amansia glomerata

Description: grows to 15cm tall is bush-like with dark red central stipe and flattened blades 3-7mm wide. Often covered with epiphytic crustose coralline seaweeds giving off a pink appearance.

Habitat: widespread in shaded areas of almost any habitat.

Centroceras clavulatum

Description: Y shaped branches and usually dark red in appearance. Size is 1mm diameter with two branches often curving upward, creating a claw-like appearance up to 0.5-5cm long.

Habitat: grows in tufts and mats in lower tidal habitats tide pools reef flats.

Laurencia nidifica

Description: round main branches 1-2mm diameter and 2-20cm long. Cylindrical branches with blunt tips with a tiny pit in each tip. Color is highly variable, often branches are rosy-straw colored with red tips.

Habitat: on reef flats and lower intertidal habitats along rocky coastlines.

Martensia fragilis

Description: flat seaweed. May be completely solid and smooth or divided into a fine lacelike network on outer portion. 1-8 cm high. Variable color: pink to orange, to bluish iridescence.

Habitat: common in tide pools and reef flats.

Spyridia filamentosa

Description: 0.5-2mm in diameter covered with any soft fine branches creating a fuzzy appearance red to almost white in color, but often traps fine sediment that can make it appear many different colors.

Habitat: in calm inner areas of reef flats. Soft thick mats can cover large areas of the reef flat.

Tolypiocladia glomerulata

Description: filamentous red that forms loose mats from 0.3-1 cm thick. Main branches are 0.5 mm in diameter with many smaller branches growing out from them. In deeper water it is dark red in shallow water it appears pale red. Has distinctive branching pattern.

Habitat: on rubble and coral heads in subtidal habitats.

Order Gelidiiales

Pterocladia caerulescens

Description: dark green to blackish color. 2cm high with flattened branches.

Habitat: common in tide pools and on reef flats.


Last update: 1/25/2005