Supplementary materials
(a)
(b)
150°E
145°E
N
N
15°S
Pioneer Bay
1
2
Cairns
Orpheus
Island
Hazard Bay
Townsville
0
20°S
150
300 km
0
1
2 km
Figure S1: Map of the Great Barrier Reef (GBR) showing the location of the study sites. (a)
Geographic location of Orpheus Island in the central GBR (b) Map of Orpheus Island showing
the location of the study sites on its leeward margin. Filled circles represent the two study sites.
Loffler, Bellwood and Hoey 2014
Galaxaura (n=20)
Proportion of pairing instances
Acanthophora (n=21)
0.6
0.6
0.5
0.5
0.4
0.4
0.3
0.3
0.2
0.2
0.1
0.1
0.0
0.0
Sargassum (n=26)
Turbinaria (n=20)
0.6
0.6
0.5
0.5
0.4
0.4
0.3
0.3
0.2
0.2
0.1
0.1
0.0
0.0
m
ra
ra
ria lgae lone
ho xau ssu ina
A
p
a
oa
a
rg Turb acr
tho Gal
a
n
S
a
rm
Ac
he
t
O
e
e
a
a
a
o r a u r s s u m na r i
ga
l
lon
h
a
i
x
A
p
a
o
b
a
o
cr
rg Tur
th G a l
Sa
an
ma
c
r
A
he
Ot
Figure S2: Frequency of naturally occurring associations between macroalgal species on the reef
within Pioneer Bay, Orpheus Island. Values are the proportion of instances Acanthophora,
Galaxaura, Sargassum, and Turbinaria thalli were found in close proximity to other macroalgae
or alone.
Loffler, Bellwood and Hoey 2014
Table S1: Relative palatability of each species of macroalgae used in the study
Algal species
Taxonomic
classification
Functional
classification
(Steneck 1988)
Defence
Acanthophora
spicifera
Rhodophyta
Corticated
None
Galaxaura
rugosa
Rhodophyta
Calcified
Calcified,
chemical
Turbinaria
ornata
Phaeophyceae
Leathery
Leathery
Sargassum sp.
Phaeophyceae
Leathery
Leathery,
chemical
Palatability
References
Readily consumed in macroalgal
feeding trials
Calcification and
allelochemicals dissuade
predation
Tough, leathery morphology,
making predation by many fish
species difficult
A dominant macroalgal species
after the occurrence of phase
shifts. Readily eaten in feeding
trials
Littler et al. 1986; Reinthal
and Macintyre 1994
Paul and Hay 1986;
Rasher et al. 2011; Rasher
et al. 2013
Littler et al. 1983
Hughes et al. 2007; Fox
and Bellwood 2008;
Cvitanovic and Bellwood
2009
Loffler, Bellwood and Hoey 2014
Methods and results for macroalgal association surveys
The frequency of associations among macroalgal species on the study reef was quantified
visually. A minimum of 20 individuals of each of the four focal macroalgal species,
Acanthophora spicifera, Galaxaura rugosa, Turbinaria ornata and Sargassum sp., were located
while conducting a haphazard swim across the mid-outer reef flat, approximately 2m deep. Due
to their size, algae greater than 3cm from the focal thalli would have been unlikely to provide or
be provided refuge. Therefore, if no algae were within 3 cm of the focal alga, it was classified as
'alone'.
These visual surveys revealed that macroalgae at our study sites are almost always found in
close association with other algae and that the three pairings selected for this study are common
among algal taxa on the reef of Pioneer Bay. Of the 20 Galaxaura thalli surveyed, 50 % were
associated with Acanthophora (ESM Fig. S2). Acanthophora was predominantly associated with
Sargassum (43 %), and was less often associated with Turbinaria (5%). Of the 26 Sargassum
thalli surveyed, most were associated with 'other' macroalgae, such as Padina sp. and Halimeda
sp., (50%), and Turbinaria (15%). Associations with Turbinaria were evenly spread with both
Sargassum (25 %) and Acanthophora (25 %) being frequently recorded in its vicinity. The four
focal species of algae were rarely found growing in isolation, with only one Acanthophora and
two Turbinaria thalli observed without other macroalgae in their immediate vicinity.
References
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of the Great Barrier Reef. Coral Reefs 28:127-133
Loffler, Bellwood and Hoey 2014
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rabbitfish Siganus canaliculatus (f: Siganidae) on an inner-shelf reef of the Great Barrier
Reef. Coral Reefs 27:605-615
Hughes TP, Rodrigues MJ, Bellwood DR, Ceccarelli D, Hoegh-Guldberg O,
McCook L,
Moltschaniwskyj N, Pratchett MS, Steneck RS, Willis B (2007) Phase shifts, herbivory
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Littler MM, Taylor, PR, Littler DS (1983) Algal resistance to herbivory on a Caribbean barrier
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Littler MM, Taylor PR, Littler DS (1986) Plant defense associations in the marine environment.
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Loffler, Bellwood and Hoey 2014