15 – Macroalgae
151
L Eucheuma: similar to some species of Hypnea but the
thalli are tougher and rubbery. Sometimes found
between branches of branched Acropora corals
(Fig. 15.1D).
L Galaxaura:
lightly
calcified,
dichotomously
branched, branches cylindrical or flattened, smooth
or hairy. Pink to red, sometimes with chalky
appearance.
L Hypnea: branches cylindrical and generally bearing
numerous relatively short spine- or tooth-like
branchlets with pointed tips. Colour variable from
pale brown to dark purple. Usually between
branches of hard corals (Fig. 15.1E).
L Jania: heavily calcified, similar to Amphiroa but plants
are smaller (few mm) and branches are predominantly cylindrical. Widespread in shallow and deep
reefs (Fig. 15.1F).
L Laurencia: plants generally bushy, branches usually
cylindrical with blunt tip branchlets. Colour variable, some with green branches and pink tips, others
ranging from orange, red to pink. Common on reef
flats (Fig. 15.1G).
L Melanamansia: red to reddish-brown, branches leaflike and grouped in rosettes, with marginal teeth.
Generally found on crevices and other low-light
microenvironments (Fig. 15.1H).
L Peyssonnelia: encrusting, rounded to fan-shaped
plants. Calcification on the lower side and fleshy
surface. Colour variable, dark red, purple pink or
red yellowish. Common on overhangs and cryptic
microhabitats (Fig. 15.1I).
L Porolithon: encrusting, heavily calcified with chalky
texture. Pink crusts of several mm thick. Common
on the reef crest (Fig. 15.1J). Other crustose coralline
algae are epiphytic (grow on the surface of other
benthic algae) (Fig. 15.1K).
L Polysiphonia: filamentous, usually a few mm tall,
examination under the microscope shows cylindrical polysiphonous branches with a ‘banding’
appearance, similar to Sphacelaria. Pink to red,
red-brown or brown. Common and abundant on
algal turfs.
Brown algae
L Dictyota: plants creeping or erect, flattened, strap or
ribbon-like (without midrib as in Dictyopteris).
Branching dichotomous (forked). Light brown and
several species with blue-green iridescence. Common (Fig. 15.1L).
L Chnoospora: plants forming mats or cushion-like
clumps, branches are slightly flattened and dichotomous. Light brown. Common on reef flats.
L Colpomenia: plants rounded or irregularly lobed with
hollow interior. Light to pale golden brown. Common on inshore reefs (Fig. 15.1M).
L Hincksia: small (few mm) filamentous plants, fine,
erect, uniseriate (one row), pale yellowish and translucent. Reproductive structures (sporangia) somewhat corn cob-like. Common on algal turfs.
L Hormophysa: similar to Sargassum but blades with internal oblong air bladders. Yellow to dark-brown.
Common on inshore refs.
L Hydroclathrus: light to pale golden brown, net-like
structure, perforated. Common on calm and sheltered waters (Fig. 15.1N).
L Lobophora variegata: creeping, rounded to fan-shaped
plants, sometimes encrusting. Pale to dark brown
and usually with concentric bands and radiating
lines. Common to locally very abundant, particularly between branches of corals (Fig. 15.1O).
L Padina: upright, sheet-like, fan-shaped plants, with
concentric bands and also whitish bands due to carbonate deposition. Similar to Lobophora but has characteristic inrolled outer margin. Common on reefs
flats (Fig. 15.2A).
L Sargassum: plants erect, leathery, some up to a couple of metres are the tallest seaweeds in the GBR.
They typically have a stipe, leaf-like fronds with a
midrib (central vein), and air vesicles or floats. Very
abundant on inshore reefs (Fig. 15.2B, C).
L Sphacelaria: filamentous, small (few mm) turfing
plants, branch cells (observed under compound microscope) arranged in regular transverse tiers,
individual cells rectangular and elongated longitudinally. Distinctive dark brown cell at the tip of each
151
L Eucheuma: similar to some species of Hypnea but the
thalli are tougher and rubbery. Sometimes found
between branches of branched Acropora corals
(Fig. 15.1D).
L Galaxaura:
lightly
calcified,
dichotomously
branched, branches cylindrical or flattened, smooth
or hairy. Pink to red, sometimes with chalky
appearance.
L Hypnea: branches cylindrical and generally bearing
numerous relatively short spine- or tooth-like
branchlets with pointed tips. Colour variable from
pale brown to dark purple. Usually between
branches of hard corals (Fig. 15.1E).
L Jania: heavily calcified, similar to Amphiroa but plants
are smaller (few mm) and branches are predominantly cylindrical. Widespread in shallow and deep
reefs (Fig. 15.1F).
L Laurencia: plants generally bushy, branches usually
cylindrical with blunt tip branchlets. Colour variable, some with green branches and pink tips, others
ranging from orange, red to pink. Common on reef
flats (Fig. 15.1G).
L Melanamansia: red to reddish-brown, branches leaflike and grouped in rosettes, with marginal teeth.
Generally found on crevices and other low-light
microenvironments (Fig. 15.1H).
L Peyssonnelia: encrusting, rounded to fan-shaped
plants. Calcification on the lower side and fleshy
surface. Colour variable, dark red, purple pink or
red yellowish. Common on overhangs and cryptic
microhabitats (Fig. 15.1I).
L Porolithon: encrusting, heavily calcified with chalky
texture. Pink crusts of several mm thick. Common
on the reef crest (Fig. 15.1J). Other crustose coralline
algae are epiphytic (grow on the surface of other
benthic algae) (Fig. 15.1K).
L Polysiphonia: filamentous, usually a few mm tall,
examination under the microscope shows cylindrical polysiphonous branches with a ‘banding’
appearance, similar to Sphacelaria. Pink to red,
red-brown or brown. Common and abundant on
algal turfs.
Brown algae
L Dictyota: plants creeping or erect, flattened, strap or
ribbon-like (without midrib as in Dictyopteris).
Branching dichotomous (forked). Light brown and
several species with blue-green iridescence. Common (Fig. 15.1L).
L Chnoospora: plants forming mats or cushion-like
clumps, branches are slightly flattened and dichotomous. Light brown. Common on reef flats.
L Colpomenia: plants rounded or irregularly lobed with
hollow interior. Light to pale golden brown. Common on inshore reefs (Fig. 15.1M).
L Hincksia: small (few mm) filamentous plants, fine,
erect, uniseriate (one row), pale yellowish and translucent. Reproductive structures (sporangia) somewhat corn cob-like. Common on algal turfs.
L Hormophysa: similar to Sargassum but blades with internal oblong air bladders. Yellow to dark-brown.
Common on inshore refs.
L Hydroclathrus: light to pale golden brown, net-like
structure, perforated. Common on calm and sheltered waters (Fig. 15.1N).
L Lobophora variegata: creeping, rounded to fan-shaped
plants, sometimes encrusting. Pale to dark brown
and usually with concentric bands and radiating
lines. Common to locally very abundant, particularly between branches of corals (Fig. 15.1O).
L Padina: upright, sheet-like, fan-shaped plants, with
concentric bands and also whitish bands due to carbonate deposition. Similar to Lobophora but has characteristic inrolled outer margin. Common on reefs
flats (Fig. 15.2A).
L Sargassum: plants erect, leathery, some up to a couple of metres are the tallest seaweeds in the GBR.
They typically have a stipe, leaf-like fronds with a
midrib (central vein), and air vesicles or floats. Very
abundant on inshore reefs (Fig. 15.2B, C).
L Sphacelaria: filamentous, small (few mm) turfing
plants, branch cells (observed under compound microscope) arranged in regular transverse tiers,
individual cells rectangular and elongated longitudinally. Distinctive dark brown cell at the tip of each