ArticlePDF Available

Abstract and Figures

The architectural complexity of ecosystems can greatly influence their capacity to support biodiversity and deliver ecosystem services. Understanding the components underlying this complexity can aid the development of effective strategies for ecosystem conservation. Caribbean coral reefs support and protect millions of livelihoods, but recent anthropogenic change is shifting communities toward reefs dominated by stress-resistant coral species, which are often less architecturally complex. With the regionwide decline in reef fish abundance, it is becoming increasingly important to understand changes in coral reef community structure and function. We quantify the influence of coral composition, diversity, and morpho-functional traits on the architectural complexity of reefs across 91 sites at Cozumel, Mexico. Although reef architectural complexity increases with coral cover and species richness, it is highest on sites that are low in taxonomic evenness and dominated by morpho-functionally important, reef-building coral genera, particularly Montastraea. Sites with similar coral community composition also tend to occur on reefs with very similar architectural complexity, suggesting that reef structure tends to be determined by the same key species across sites. Our findings provide support for prioritizing and protecting particular reef types, especially those dominated by key reef-building corals, in order to enhance reef complexity.
Content may be subject to copyright.
Ecological Applications, 21(6), 2011, pp. 2223 –2231
Ó2011 by the Ecological Society of America
Coral identity underpins architectural complexity on Caribbean reefs
LORENZO ALVAREZ-FILIP,
1,2,4
NICHOLAS K. DULVY,
2
ISABELLE M. Cˆ
oTE
´,
2
ANDREW R. WATKINSON,
3
AND JENNIFER A. GILL
1
1
Centre for Ecology, Evolution, and Conservation, School of Biological Sciences, University of East Anglia,
Norwich NR4 7TJ United Kingdom
2
Earth to Ocean Research Group, Department of Biological Sciences, Simon Fraser University,
Burnaby, British Columbia V5A 1S6 Canada
3
School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ United Kingdom
Abstract. The architectural complexity of ecosystems can greatly influence their capacity to
support biodiversity and deliver ecosystem services. Understanding the components underlying
this complexity can aid the development of effective strategies for ecosystem conservation.
Caribbean coral reefs support and protect millions of livelihoods, but recent anthropogenic
change is shifting communities toward reefs dominated by stress-resistant coral species, which are
often less architecturally complex. With the regionwide decline in reef fish abundance, it is
becoming increasingly important to understand changes in coral reef community structure and
function. We quantify the influence of coral composition, diversity, and morpho-functional traits
on the architectural complexity of reefs across 91 sites at Cozumel, Mexico. Although reef
architectural complexity increases with coral cover and species richness, it is highest on sites that
are low in taxonomic evenness and dominated by morpho-functionally important, reef-building
coral genera, particularly Montastraea. Sites withsimilar coral community composition also tend
to occur on reefs with very similar architectural complexity, suggesting that reef structure tends to
be determined by the same key species across sites. Our findings provide support for prioritizing
and protecting particular reef types, especially those dominated by key reef-building corals, in
order to enhance reef complexity.
Key words: biodiversity; coral; Cozumel, Mexico; dominance; functional groups; habitat complexity;
landscape ecology; reef.
INTRODUCTION
The architectural complexity of ecosystems often
underpins the biodiversity and ecosystem services that
they support. Architectural complexity is very often
defined or provided by foundation taxa (e.g., trees,
oysters, stony corals) that have a disproportionate
influence on ecosystem structure, function, and stability
(MacArthur 1984, Bruno and Bertness 2001, Ellison et al.
2005). However, within these broad groups of foundation
taxa, different species can contribute disproportionately
to architectural complexity. Species identity and domi-
nance have been reported as important determinants of
ecosystem functions and processes (e.g., terrestrial grass-
land, soil ecosystems; Tilman et al. 1997, McLaren and
Turkington 2010); however, studies that directly examine
the role of the type, rather than the number, of species on
habitat facilitation are rare. Understanding the influence
of different species and taxa on ecosystem structure and
function is not only of fundamental ecological interest but
can underpin the development of effective conservation
priorities and actions.
Coral reefs are among the most rapidly changing and
valuable ecosystems in the world. It is estimated that
nearly 70%of the world’s coral reefs are threatened by
anthropogenic activities (Wilkinson 2008) and are expe-
riencing unprecedented rates of degradation (Veron
2008). In the Caribbean, for instance, the architectural
complexity ofreefs has declined substantially over the past
40 years with the loss of ;80%of the most complex reefs
(Alvarez-Filip et al. 2009a). Because of the importance of
reef-building corals as foundation species within the
diverse reef ecosystem, patterns of degradation and
ecological resilience on coral reefs are typically measured
through changes in overall coral cover (e.g., Gardner et al.
2003, Bruno and Selig 2007, Mumby et al. 2007).
However, changes in coral cover often do not capture
the changes in reef architectural complexity (Alvarez-Filip
et al., in press) that can underpin a suite of important
ecosystem services, such as the dissipation of wave energy;
nutrient recycling; and the abundance, diversity, and
trophic structure of coral reef fishes (Szmant 1997, Lugo-
Fernandez et al. 1998, Sheppard et al. 2005, Wilson et al.
2007, 2010).
There is considerable potential for taxon identity and
the composition of reef-building corals to influence the
architectural complexity of reefs because hard sclerac-
Manuscript received 8 August 2010; revised 26 January 2011;
accepted 22 February 2011. Corresponding Editor: T. E.
Essington.
4
Present address: Department of Biological Sciences,
Simon Fraser University, 8888 University Drive, Burnaby,
British Columbia V5A 1S6 Canada.
E-mail: lorenzoaf@gmail.com
2223
tinian corals are a taxonomically and morphologically
diverse group (Veron and Stafford-Smith 2002, Dullo
2005). While qualitative differences in the relative
contribution of different coral species to reef complexity
are readily apparent, the contribution of coral identity
and community composition to architectural complexity
has yet to be quantified at the larger reef scales.
Quantifying the relative contribution of different coral
species to the architectural complexity of the reefscape is
therefore particularly important in order to understand
the trajectory of coral reefs under changing environ-
mental conditions.
Disturbances commonly favor a few species that are
able to competitively dominate the landscape (Tilman
and Lehman 2001, Seabloom et al. 2003). Although the
Caribbean underwent rapid losses of the structurally
important Acroporid corals in the late 1970s, many reefs
remained dominated by healthy populations of the other
major reef-building coral Montastraea (e.g., McClana-
han and Muthiga 1998), suggesting that reef complexity
could be maintained to some degree in reefs across the
region. Since then, the spread of several recently
emerged diseases, combined with recent bleaching events
and other biotic disturbances, are fostering high rates of
mortality of Montastraea and other coral species
previously thought to be more resistant to disturbance
(Weil 2004, Bruckner and Bruckner 2006 ). Throughout
the Caribbean, the loss of these main reef-building coral
species (Acropora and Montastraea) has been accompa-
nied by an increase in the relative abundance (often
leading to eventual dominance) of stress-tolerant, early-
colonizing corals that form smaller and less architectur-
ally complex colonies, such as Porites and Agaricia
(Jackson 2001, Aronson et al. 2002, Green et al. 2008,
Lirman and Manzello 2009). This shift toward weedy
coral species may constrain reefs to a state of lower
potential architectural complexity (Steneck et al. 2009),
even if overall coral cover remains stable.
Here we explore the contribution of coral community
composition to reef architectural complexity across a
broad range of sites in Cozumel, Mexico. First, we
quantify whether sites with similar coral community
composition also tend to be similar in terms of
architectural complexity. Second, we test whether greater
coral species diversity is related to greater architectural
complexity. Finally, we explore how the taxonomic and
functional attributes of coral dominance influence the
relationship between coral cover and architectural
complexity.
MATERIALS AND METHODS
Study area
Cozumel is a continental island 18 km off the
northeastern coast of the Mexican Peninsula of
Yucatan. The island is surrounded by coral reefs. The
most developed formations are in the western shelf,
where three terraces can be found between 5 m below sea
level and the shelf edge (;20 m). Unlike many other
Caribbean reefs that originally comprised Acroporid
species, in Cozumel the reefs close to the shore have been
built mainly by Montastraea (Muckelbauer 1990). The
southwestern coast of Cozumel has been under official
protection since 1980 (Alvarez-Filip et al. 2009b; Fig. 1),
and while visitation and tourist activities are permitted,
fishing is banned on the western coast of the marine
reserve.
Field surveys
In total, 91 sites along the southwestern coast of
Cozumel, all separated by at least 200 m (Fig. 1), were
surveyed between October 2007 and February 2008. At
each site, one 30-m transect was haphazardly located on
the top of the reef crest (between 10 and 15 m depth) and
parallel to the coast. Reef attributes such as coral cover
or reef architecture were not used to determine the
position of transects. To evaluate coral abundance, we
used the point intercept method to record the occurrence
of corals every 25 cm along each transect (120 counts per
transect). This method is widely used in the Caribbean
and elsewhere to describe reef benthic composition, and
it has been shown to provide comparable information to
measuring benthic composition along the entire length
of transects (Hill and Wilkinson 2004). All corals were
identified in the field at species level according to Veron
and Stafford-Smith (2002).
Reef architectural complexity was quantified using the
rugosity index (Risk 1972), which was obtained by
fitting a fine, 3-m chain (0.7 cm link length) to the reef.
While laying the chain, care was taken to follow the
detailed contour of corals and other reef attributes (rock
crevices, sponges) by lining up individual branches and
fitting the chain between coral ramets. To calculate the
index, the contoured distance was divided by the linear
distance between its start and end point. A perfectly flat
surface has a rugosity index of one, with larger numbers
indicating more complex surfaces. Rugosity measures
were taken in five equally spaced points along the same
30-m transect, which were then averaged to give
transect-level rugosity.
Data analyses
To examine whether transects with similar coral
community composition also tended to have similar
architectural complexity, we constructed matrices of site
community composition and site rugosity for all pairs of
sites. The similarity matrix for coral community
composition was constructed using all coral species
and their relative cover in each site and computed using
the Bray-Curtis similarity coefficient. The architectural
complexity matrix was constructed by calculating the
relative percentage similarity in rugosity between each
pair of sites using the following formula:
% similarity ¼ðjRiRjj=MDÞ3100
where jR
i
R
j
jis the absolute difference between the
values of rugosity in site
i
and site
j
for each pair of sites,
LORENZO ALVAREZ-FILIP ET AL.2224 Ecological Applications
Vol. 21, No. 6
and MD is the maximum observed difference between
all the pairwise comparisons. We evaluated whether
architectural complexity among sites is a function of
coral community composition among sites using a
Mantel test (Mantel 1967 ). This test measures the
correlation between two matrices and assesses the
significance of the correlation by randomizing one of
the matrices and calculating a null distribution of values
from the randomly generated associations. In this study,
the Mantel test was calculated using the package Vegan
in R (R Development Core Team 2009), with 10 000
random matrix permutations used to assess significance
levels.
To test whether greater coral species diversity is
related to greater architectural complexity, we quantified
coral diversity using three univariate dimensions of
diversity: coral species richness (number of species
recorded at each site), evenness in species abundance
(the Pielou index of percentage areal cover of each
species), and taxonomic diversity. For the last dimen-
sion, we calculated the average taxonomic distinctness
(D
þ
) and the variation in taxonomic distinctness (K
þ
)
with a widely used and accepted coral taxonomy (Veron
and Stafford-Smith 2002). Average taxonomic distinct-
ness measures average evolutionary relatedness as the
mean path (or branch) length of the local community,
and the variation in taxonomic distinctness is the
variance in path (or branch) lengths of the local
community (Clarke and Warwick 2001). We also
calculated richness and evenness of the morpho-func-
tional groups. We then used linear regressions to explore
the strength and nature of the associations between each
of these measures of coral diversity and reef architec-
tural complexity.
To explore the influence of species identity and
morpho-functional attributes on reef structure, we
grouped coral species by genus and by morphology.
Morpho-functional groups were constructed from the
maximum size and colony shape of each coral species
(Table 1). Following Reyes-Bonilla (2004 ), three shape
categories (massive or nodular; branching, ramose, or
phaceloid; platy, foliaceous, or encrusting) and three size
categories (small, ,10 cm; medium, 10–30 cm; large,
.30 cm) were used. Combining shape and size
categories resulted in seven different morpho-functional
groups (Table 1).
To explore how the taxonomic and functional
attributes of coral dominance influence the relationship
between coral cover and architectural complexity, we
compared the slopes of these relationships among (a) the
three most abundant genera (Agaricia,Porites, and
Montastraea) and (b) the three most abundant morpho-
functional groups (Fig. 2B). The 91 transects were
categorized depending on the single most-dominant
(highest relative abundance on the site) genus and
morpho-functional group. Differences between each
pair of linear models were explored by dividing the
difference between both regression coefficients by the
square root of the sum of the squared standard errors.
Assuming normally distributed residuals, this estimate
follows a tdistribution with n2 degrees of freedom
(Zar 1999).
FIG. 1. Map of Cozumel Island, Mexico, and (inset) the location within the Caribbean Sea. The continuous line delimits the
polygon of the Marine Protected Area (Parque Nacional Arrecifes de Cozumel), and the bold dotted line represents the area
surveyed in this study.
September 2011 2225CORAL IDENTITY UNDERPINS REEF COMPLEXITY
RESULTS
A total of 33 species of reef-building corals were
recorded in Cozumel during this study (Table 1). The
dominant genera included Agaricia,Montastraea, and
Porites (primarily P. astreoides), and hence corals with
large, massive, and foliaceous colonies were the most
abundant morpho-functional groups (Fig. 2A, B). Both
coral cover and reef architectural complexity varied
greatly across the study area, from flat sites with low
coral cover to highly complex areas of reef. Coral cover
for the 91 sites was 16%61.32%(mean 6SE; range: 0%
to 52%), while rugosity averaged 1.49 60.04 (range 1.02
to 2.77).
Pairs of sites with similar coral community composi-
tion tended also to have similar levels of architectural
complexity (Mantel test r
m
¼0.18; P,0.001). Very high
similarity in coral community composition (.70%)
occurred only in reefs with similar architectural com-
plexity (.50%similarity in rugosity) regardless of
whether the sites were similarly complex or similarly
flat (Fig. 3).
Architectural complexity was positively associated
with the number of coral species; sites with fewer than
five coral species tended to be relatively flat, while more
diverse sites, with between eight and 13 species, had the
greatest complexity (Fig. 4A). However, the evenness in
coral cover among coral species declined with increasing
coral species richness (r¼0.40; P,0.001), and
consequently sites with greater architectural complexity
tended to be species rich but dominated by one or a few
coralspecies(Fig.4B).Theflatreefsprimarily
comprised bare rock and/or algae rather than mono-
typic patches of relatively flat corals (e.g., Millepora or
Siderastrea), as indicated by the lack of any sites with
high coral cover and low rugosity (Fig. 4A). The
relationship between taxonomic distinctness among
coral species and architectural complexity was highly
nonlinear (R
2
¼0.01; P¼0.22), with a small number of
flat reefs tending to be either particularly distinct or
particularly related (Fig. 3C). The variation in taxo-
nomic distinctness was not significantly related to
architectural complexity (Fig. 4D). From the morpho-
logical and functional perspective, the greatest complex-
ity was found on reefs with higher morpho-functional
diversity (Fig. 4E) but dominated by relatively few
morpho-functional types (Fig. 4F).
Reefs with greater coral cover tended to have greater
architectural complexity, but the variance in architec-
TABLE 1. Cover and morphological information of the coral species recorded in the 91 sites surveyed on Cozumel Island, Mexico.
Genus Species Mean cover (%)Colony shapeàColony size§ Morphological group}
Acropora A. cervicornis 0.03 (0.03) B L BL
A. palmata 0.16 (0.1) B L BL
Madracis M. decactis 0.16 (0.04) M M MM
M. formosa 0.02 (0.01) B M BM
Stephanocoenia S. intersepta 0.24 (0.05) M M MM
Eusmilia E. fastigiata 0.39 (0.07) B M BM
Colpophyllia C. natans 0.06 (0.04) M L ML
Diploria D. clivosa 0.03 (0.02) M L ML
D. labyrinthiformis 0.05 (0.02) M M MM
D. strigosa 0.07 (0.04) M M MM
Montastraea M. annularis 1.43 (0.39) M L ML
M. cavernosa 0.97 (0.12) M L ML
M. faveolata 1.68 (0.26 ) M L ML
M. franksi 0.09 (0.03) M M MM
Favia F. fragum 0.02 (0.01) M S MS
Dendrogyra D. cylindrus 0.01 (0.01) M L ML
Dichocoenia D. stokesii 0.04 (0.02) M M MM
Meandrina M. meandrites 0.13 (0.04) M M MM
Isophyllastrea I. rigida 0.02 (0.01) M M MM
Mycetophyllia M. lamarckiana 0.15 (0.04) P M PM
Agaricia A. agaricites 4.56 (0.41) P L PL
A. humilis 0.03 (0.02) M L ML
A. lamarcki 0.02 (0.01) P L PL
A. tenuifolia 0.43 (0.13) P L PL
Siderastrea S. radians 0.02 (0.01) M S MS
S. siderea 1.45 (0.16) M L ML
Porites P. astreoides 2.45 (0.3) M M MM
P. colonensis 0.03 (0.02) P M PM
P. divaricata 0.02 (0.01) B L BL
P. furcata 0.10 (0.04) B L BL
P. porites 0.82 (0.13) B L BL
Millepora M. alcicornis 0.27 (0.06) B M BM
M. complanta 0.06 (0.02) P L PL
SE in parentheses.
àB, branching, ramose, or phaceloid; M, massive or nodular; P, platy, foliaceous, or encrusting.
§ S, small (,10 cm); M, medium (10–30 cm); L, large (.30cm).
}Morphological group is the combination of shape and size.
LORENZO ALVAREZ-FILIP ET AL.2226 Ecological Applications
Vol. 21, No. 6
tural complexity also increased with coral cover (Fig.
5A). Much of the variance in architectural complexity at
high levels of coral cover was the result of dominance by
a particular coral genus. Sites dominated by species from
the genus Montastraea had greater architectural com-
plexity for a given coral cover, followed by Agaricia,
then Porites (Fig. 5B). On Montastraea-dominated sites,
architectural complexity increased more rapidly with
increasing coral cover than on Porites-dominated sites
(T
24
¼2.23; P¼0.03). However, the slopes of
relationships between coral cover and architectural
complexity for Agaricia and each of the other two
genera did not differ significantly (Agaricia vs.
Montastraea T
49
¼1.65, P¼0.10; Agaricia vs. Porites
T
47
¼1.23, P¼0.22).
The differences in architectural complexity for given
levels of coral cover are also strongly related to the
morpho-functional attributes of the dominant species.
Sites dominated by massive and large coral species have
greater architectural complexity for a given coral cover,
followed by sites dominated by large platy, foliaceous,
or encrusting (PL) and then medium-sized massive
corals (Fig. 5C ). Architectural complexity on sites
dominated by massive and large (ML) coral species also
increased significantly more rapidly with increasing
coral cover than on reefs dominated by medium-sized
massive corals (T
34
¼2.72, P¼0.01). However, the
slope of the relationship between architectural complex-
ity and coral cover on large platy, foliaceous, or
encrusting-dominated reefs did not differ significantly
from the other two morphological groups (PL vs. ML
T
54
¼1.56, P¼0.13; PL vs. MM [massive medium-sized]
T
30
¼0.81, P¼0.43).
DISCUSSION
Our findings suggest that the type and dominance of
foundation species can be just as important as their
overall abundance in providing architectural complexity
to their ecosystems. Reef complexity increases with
increasing coral cover, but the rate of increase in
complexity depends on coral community composition
and, in particular, the identity of the dominant species
and their associated morphological and functional traits.
The most architecturally complex sites are dominated by
few coral species (and morpho-functional groups), and
the identity of these corals largely explains the differ-
ences in the architecture of these sites. These findings
underscore the importance of considering coral species
composition and shifts in coral dominance on Caribbean
reefs in order to understand the implications of changes
in these ecosystems on the associated biodiversity and
ecosystem services.
Generally, species diversity is considered a fundamen-
tal feature of ecosystem structure and function (Loreau
et al. 2001, Hooper et al. 2005), and in coral reefs, greater
species diversity might be expected to increase reef
complexity simply because of the large variety of coral
FIG. 2. Cover (mean þSE) of hard corals on Cozumel reefs,
grouped by (A) genus and (B) morphology (see Table 1 for
definitions of morpho-functional groups). For panel (B) the
total number of species included in each morpho-functional
group is given in parentheses.
FIG. 3. Similarities in coral community composition (Bray-
Curtis similarity coefficient) and reef architecture (similarity in
rugosity indices) for 4095 different pairs of sites from 91 sites in
Cozumel. Circle shading indicates pairs of sites that both have
rugosity values .1.5 (black), both ,1.5 (gray), or one from
each category (white).
September 2011 2227CORAL IDENTITY UNDERPINS REEF COMPLEXITY
forms and shapes (e.g., Chabanet et al. 1997, Bruno and
Bertness 2001). However, positive relationships between
the number of coral species and architectural complexity
may, in fact, be a consequence of the positive relationship
between coral cover and architectural complexity, as
species diversity can also be positively associated with the
extent of coral cover (this study, r¼0.83, P,0.001)
(Bell and Galzin 1984). Moreover, taxonomic related-
ness indices showed that most sites shared a very similar
species composition and that there was no clear effect of
increasing taxonomic composition on reef architectural
complexity. By contrast, the distribution of species
relative abundances (percent cover) clearly showed that
predominance by one or few species increased the
complexity of the reef structure. Historically, Carib-
bean reefs have comprised small numbers of abundant
species rather than a high diversity of coral species
(Johnson et al. 2008), supporting the importance of coral
FIG. 4. The relationships between reef architectural complexity on 91 sites in Cozumel and (A) total number of coral species ( y
¼1.06 þ0.08x,R
2
¼0.34; P,0.001); (B) Pielou index of coral species evenness (y¼3.99 2.79x,R
2
¼0.30; P,0.001); (C)
average taxonomic distinctness of coral species; (D) variation in taxonomic distinctness of coral species; (E) total number of coral
morpho-functional groups (y¼0.79 þ0.19x,R
2
¼0.33; P,0.001); and (F) Pielou index of morpho-functional groups evenness ( y
¼4.08 2.90x,R
2
¼0.32; P,0.001).
LORENZO ALVAREZ-FILIP ET AL.2228 Ecological Applications
Vol. 21, No. 6
dominance in their structure. In addition, Caribbean
corals have relatively low diversity and redundancy in
comparison with other regions of the world. For
example, there are 120 massive coral species in
Australia’s Great Barrier Reef, while the Caribbean
harbors ,25 (Bellwood et al. 2004). This lack of
functional diversity might explain why Caribbean reef
architectural complexity relies more on the presence and
identity of dominant species than on the combined
structural attributes of a wider range of species.
We found that the strength of the positive effect of
foundation species in providing structure to the habitat
largely depends on the identity of the dominant taxa. At
the reefscape scale, architectural complexity increased
faster in sites dominated by large, massive species, such
as Montastraea, than in sites dominated by short-lived
and stress-resistant species. Branching corals are rela-
tively uncommon in Cozumel; for example, branching
species of the genus Porites (P. porites) occur at much
lower relative abundance than the sister massive species
(P. astreoides; Table 1), and the main differences in reef
complexity found in this study are therefore primarily a
consequence of the largeandmassivenatureof
Montastraea corals. Among Caribbean reef-building
corals, Montastraea spp. play critical roles in reef
construction and community ecology (Harborne et al.
2008, Harborne 2009). The relative abundance of such
massive species is declining in the Caribbean (Edmunds
and Elahi 2007). For example, Cozumel reefs were
largely dominated by Montastraea spp. in the 1980s
(Muckelbauer 1990) but more recently they are increas-
ingly dominated by Agaricia and Porites (Alvarez-Filip
et al. 2009b; Fig. 2). Cozumel reefs may therefore no
longer be providing the structural benefits that they were
in recent decades. Similar shifts from assemblages
dominated by physically large and long-lived coral
species toward assemblages dominated by weedy corals
are being recorded throughout the Caribbean (Jackson
2001, Aronson et al. 2002, Green et al. 2008, Lirman and
Manzello 2009, Steneck et al. 2009), highlighting the
large-scale consequences that these changes in coral
community composition may have for the architectural
complexity of Caribbean reefs.
On sites with relatively low coral cover (20 %),
architectural complexity varies little, even across sites
dominated by different coral species and types (Fig. 5B,
C), probably because dominant species are not abun-
dant enough (high evenness; Fig. 5A) to contribute
significantly to the reef framework. Assuming that this
also applies elsewhere in the Caribbean, our findings
may help to explain the rapid structural homogenization
toward relatively flat reefs reported in recent decades
(Alvarez-Filip et al. 2009a). Most Caribbean reefs have
been near or below 20%coral cover since the early 2000s
(Gardner et al. 2003, Bruno et al. 2009, Schutte et al.
2010), which may suggest that the abundance of
previously dominant corals in most reefs is now too
low to contribute significantly to reef architectural
FIG. 5. (A) The relationship between coral cover and
architectural complexity indices across 91 sites in Cozumel
(R
2
¼0.61, slope ¼0.024; P,0.001) for sites dominated by
Montastraea (black), Agaricia (dark gray), Porites (pale gray),
or no dominant species (white). Increasing symbol size
represents increasing evenness (Pielou index) of coral commu-
nity composition. (B) The linear regression and 95%confidence
intervals for sites dominated by the three most common coral
genera: Montastraea (y¼1.02 þ0.04x,R
2
¼0.61; P,0.001),
Agaricia (y¼1.12 þ0.02x,R
2
¼0.55; P,0.001), and Porites (y
¼1.05 þ0.02x,R
2
¼0.84; P,0.001). (C) The linear regression
and 95%confidence intervals for coral morphological groups:
massive-large (y¼1.05 þ0.03x,R
2
¼0.62; P,0.001), platy-
large (y¼1.16 þ0.02x,R
2
¼0.50; P,0.001), and massive-
medium (y¼1.02 þ0.02x,R
2
¼0.93; P,0.001). See Table 1
for details of morphological groups.
September 2011 2229CORAL IDENTITY UNDERPINS REEF COMPLEXITY
complexity. It is likely that the high frequency of
disturbances or chronic mortality that Caribbean reefs
face may prevent some structurally important species
from dominating (Hughes and Connell 1999), and these
reefs are therefore likely to remain in the current state of
low complexity and high evenness.
More complex reefs tend to have greater numbers of
individuals, biomass, or richness of reef-associated fishes
and invertebrates (Dulvy et al. 2002, Idjadi and
Edmunds 2006, Wilson et al. 2007). Consequently, our
findings suggest that assemblages with dominant reef-
building species such as Montastraea spp. would be
expected to facilitate more biodiverse and functionally
important coral reefs in the Caribbean. Montastraea
historically ranked high in importance along with
Acropora palmata and A. cervicornis in overall contri-
bution to Western Atlantic reef structure. Acroporids
have now almost vanished from Caribbean reefs, and
the unique structural role (i.e., large-branching colonies)
of these corals is likely no longer filled by any other
species (Bruckner 2003, Aronson and Precht 2006 ). In
the Caribbean, therefore, it is likely that halting rates of
architectural complexity loss will require a major
emphasis on facilitating the maintenance and endurance
of healthy populations of Montastraea corals and
promoting the recovery of Acroporids, rather than just
focusing efforts on restoring the overall abundance of
scleractinian corals. This seems to be particularly
important for those reefs that have relatively high coral
cover (.20%), where the presence of healthy popula-
tions of these key coral species may considerably
increase the reef architectural complexity. Important
regional differences in the species richness and function-
al composition of reef systems (Bellwood et al. 2004)
also highlight the need to explore the generality of these
findings. Assessing whether similar patterns occur in
regions with considerably higher diversity of coral forms
and functional redundancy, such as in the Indo-West
Pacific, would enrich our understanding of the role of
coral species composition in the provision of ecological
and ecosystem services.
ACKNOWLEDGMENTS
This study was carried out with the permission and support
of the Parque Nacional Arrecifes de Cozumel and the Comisio
´n
Nacional de A
´reas Naturales Protegidas of Mexico. We thank
M. Millet-Encalada, R. Hernandez-Landa, A. Brito-Bermudez,
and the staff of the PNAC for their invaluable help during the
surveys. This research was funded by the Mexican scholarships
from the CONACYT (171864) and SEP to Lorenzo Alvarez-
Filip. Nicholas K. Dulvy and Isabelle M. C ˆ
ote
´were supported
by Discovery grants from the Natural Sciences and Engineering
Research Council, Canada, and Jennifer A. Gill was supported
by the Natural Environment Research Council, United
Kingdom. Our manuscript was significantly improved by
insightful comments of two anonymous referees.
LITERATURE CITED
Alvarez-Filip, L., I. M. Cˆ
ote
´, J. A. Gill, A. R. Watkinson, and
N. K. Dulvy. In press. Region-wide temporal and spatial
variation in Caribbean reef architecture: is coral cover the
whole story? Global Change Biology. [doi:10.1111/j.
1365-2486.2010.02385.x]
Alvarez-Filip, L., N. K. Dulvy, J. A. Gill, I. M. Cˆ
ote
´, and A. R.
Watkinson. 2009a. Flattening of Caribbean coral reefs:
region-wide declines in architectural complexity. Proceedings
of the Royal Society B 276:3019–3025.
Alvarez-Filip, L., M. Millet-Encalada, and H. Reyes-Bonilla.
2009b. Impact of hurricanes Emily and Wilma on the coral
community of Cozumel Island, Mexico. Bulletin of Marine
Science 84:295–306.
Aronson, R. B., I. G. Macintyre, W. F. Precht, T. J. T.
Murdoch, and C. M. Wapnick. 2002. The expanding scale of
species turnover events on coral reefs in Belize. Ecological
Monographs 72:233–249.
Aronson, R. B., and W. F. Precht. 2006. Conservation,
precaution, and Caribbean reefs. Coral Reefs 25:441–450.
Bell, J. D., and R. Galzin. 1984. Influence of live coral cover on
coral reef fish communities. Marine Ecology Progress Series
15:265–274.
Bellwood, D. R., T. P. Hughes, C. Folke, and M. Nystrom.
2004. Confronting the coral reef crisis. Nature 429:827–833.
Bruckner, A. W. 2002. Proceedings of the Caribbean Acropora
Workshop: potential application of the U.S. Endangered
Species Act as a conservation strategy. NOAA Technical
Memorandum NMFS-OPR-24. Silver Spring, Maryland,
USA.
Bruckner, A. W., and R. J. Bruckner. 2006. The recent decline
of Montastraea annularis (complex) coral populations in
western Curac¸ ao: a cause for concern? Revista de Biologia
Tropical 54:45–58.
Bruno, J. F., and M. D. Bertness. 2001. Habitat modification
and facilitation in benthic marine communities. Pages 201–
218 in M. D. Bertness, S. D. Gaines, and M. E. Hay, editors.
Marine community ecology. Sinauer, Sunderland, Massa-
chusetts, USA.
Bruno, J. F., and E. Z. Selig. 2007. Regional decline of coral
cover in the Indo-Pacific: timing, extent, and subregional
comparisons. PLoS ONE 2:e711.
Bruno, J. F., H. Sweatman, W. F. Precht, E. R. Selig, and
V. G. W. Schutte. 2009. Assessing evidence of phase shifts
from coral to macroalgal dominance on coral reefs. Ecology
90:1478–1484.
Chabanet, P., H. Ralambondrainy, M. Amanieu, G. Faure, and
R. Galzin. 1997. Relationships between coral reef substrata
and fish. Coral Reefs 16:93–102.
Clarke, K. R., and R. M. Warwick. 2001. A further biodiversity
index applicable to species lists: variation in taxonomic
distinctness. Marine Ecology Progress Series 216:265–278.
Dullo, W. C. 2005. Coral growth and reef growth: a brief
review. Facies 51:37–52.
Dulvy, N. K., R. E. Mitchell, D. Watson, C. J. Sweeting, and
N. V. C. Polunin. 2002. Scale-dependant control of motile
epifaunal community structure along a coral reef fishing
gradient. Journal of Experimental Marine Biology and
Ecology 280:137–139.
Edmunds, P. J., and R. Elahi. 2007. The demographics of a 15-
year decline in cover of the Caribbean reef coral Montastraea
annularis. Ecological Monographs 77:3–18.
Ellison, A. M. et al. 2005. Loss of foundation species:
consequences for the structure and dynamics of forested
ecosystems. Frontiers in Ecology and the Environment
3:479–486.
Gardner, T. A., I. M. Cˆ
ote
´, J. A. Gill, A. Grant, and A. R.
Watkinson. 2003. Long-term region-wide declines in Carib-
bean corals. Science 301:958–960.
Green, D. H., P. J. Edmunds, and R. C. Carpenter. 2008.
Increasing relative abundance of Porites astreoides on
Caribbean reefs mediated by an overall decline in coral
cover. Marine Ecology Progress Series 359:1–10.
Harborne, A. R. 2009. First among equals: why some habitats
should be considered more important than others during
LORENZO ALVAREZ-FILIP ET AL.2230 Ecological Applications
Vol. 21, No. 6
marine reserve planning. Environmental Conservation 36:87–
90.
Harborne, A. R., P. J. Mumby, C. V. Kappel, C. P. Dahlgren,
F. Micheli, K. E. Holmes, and D. R. Brumbaugh. 2008.
Tropical coastal habitats as surrogates of fish community
structure, grazing, and fisheries value. Ecological Applica-
tions 18:1689–1701.
Hill, J., and C. Wilkinson. 2004. Methods for ecological
monitoring of coral reefs. Australian Institute of Marine
Science, Townsville, Queensland, Australia.
Hooper, D. U., et al. 2005. Effects of biodiversity on ecosystem
functioning: a consensus of current knowledge. Ecological
Monographs 75:3–35.
Hughes, T. P., and J. H. Connell. 1999. Multiple stressors on
coral reefs: a long-term perspective. Limnology and Ocean-
ography 44:932–940.
Idjadi, J. A., and P. J. Edmunds. 2006. Scleractinian corals as
facilitators for other invertebrates on a Caribbean reef.
Marine Ecology Progress Series 319:117–127.
Jackson, J. B. C. 2001. What was natural in the coastal oceans?
Proceedings of the National Academy of Sciences USA
98:5411–5418.
Johnson, K. G., J. B. C. Jackson, and A. F. Budd. 2008.
Caribbean reef development was independent of coral
diversity over 28 million years. Science 319:1521–1523.
Lirman, D., and D. Manzello. 2009. Patterns of resistance and
resilience of the stress-tolerant coral Siderastrea radians
(Pallas) to sub-optimal salinity and sediment burial. Journal
of Experimental Marine Biology and Ecology 369:72–77.
Loreau, M., S. Naeem, P. Inchausti, J. Bengtsson, J. P. Grime,
A. Hector, D. U. Hooper, M. A. Huston, D. Rafaelli, B.
Schmid, D. Tilman, and D. A. Wardle. 2001. Biodiversity
and ecosystem functioning: current knowledge and future
challenges. Science 294:804–808.
Lugo-Fernandez, A., H. H. Roberts, and J. N. Suhayda. 1998.
Wave transformations across a Caribbean fringing-barrier
coral reef. Continental Shelf Research 18:1099–1124.
MacArthur, R. H. 1984. Geographical ecology, patterns in the
distribution of species. Princeton University Press, Princeton,
New Jersey, USA.
Mantel, N. 1967. The detection of disease clustering and a
generalized regression approach. Cancer Research 27:209–
220.
McClanahan, T. R., and N. A. Muthiga. 1998. An ecological
shift in a remote coral atoll of Belize over 25 years.
Environmental Conservation 25:122–130.
McLaren, J. R., and R. Turkington. 2010. Plant functional
group identity differentially affects leaf and root decompo-
sition. Global Change Biology 98:459–469.
Muckelbauer, G. 1990. The shelf of Cozumel, Mexico:
topography and organisms. Facies 23:185–200.
Mumby, P. J., A. Hastings, and H. J. Edwards. 2007.
Thresholds and the resilience of Caribbean coral reefs.
Nature 450:98–101.
R Development Core Team. 2009. R: a language and
environment for statistical computing. R Foundation for
Statistical Computing, Vienna, Austria. hwww.r-project.comi
Reyes-Bonilla, H. 2004. Biogeography and diversity of reef
corals of the Eastern Pacific and Western Atlantic. Disser-
tation. University of Miami, Miami, Florida, USA.
Risk, M. J. (1972). Fish diversity on a coral reef in the Virgin
Islands. Atoll Research Bulletin 193:1–6.
Schutte, V. G. W., E. R. Selig, and J. F. Bruno. 2010. Regional
spatio-temporal trends in Caribbean coral reef benthic
communities. Marine Ecology Progress Series 402:115–122.
Seabloom, E. W., E. T. Borer, V. L. Boucher, R. S. Burton,
K. L. Cottingham, L. Goldwasser, W. K. Gram, B. E.
Kendall, and F. Micheli. 2003. Competition, seed limitation,
disturbance, and reestablishment of California native annual
forbs. Ecological Applications 13:575–592.
Sheppard, C., D. J. Dixon, M. Gourlay, A. Sheppard, and R.
Payet. 2005. Coral mortality increases wave energy reaching
shores protected by reef flats: examples from the Seychelles.
Estuarine Coastal and Shelf Science 64:223–234.
Steneck, R. S., C. B. Paris, S. N. Arnold, M. C. Ablan-Lagman,
A. C. Alcala, M. J. Butler, L. J. McCook, G. R. Russ, and
P. F. Sale. 2009. Thinking and managing outside the box:
coalescing connectivity networks to build region-wide resil-
ience in coral reef ecosystems. Coral Reefs 28:367–378.
Szmant, A. M. 1997. Nutrient effects on coral reefs: a
hypothesis on the importance of topographic and trophic
complexity to reef nutrient dynamics. Pages 1527–1532 in 8th
International Coral Reef Symposium. Smithsonian Tropical
Research Institute, Panama.
Tilman, D., J. Knops, D. Wedin, P. Reich, M. Ritchie, and E.
Siemann. 1997. The influence of functional diversity and
composition on ecosystem processes. Science 277:1300–1302.
Tilman, D., and C. Lehman. 2001. Human-caused environ-
mental change: impacts on plant diversity and evolution.
Proceedings of the National Academy of Sciences USA
98:5433–5440.
Veron, J. E. N. 2008. Mass extinctions and ocean acidification:
biological constraints on geological dilemmas. Coral Reefs
27:459–472.
Veron, J., and M. Stafford-Smith. 2002. Coral ID: an electronic
key to the zooxanthellate scleratinian corals of the world.
Australian Institute of Marine Science, Townsville, Australia.
Weil, E. 2004. Coral reef diseases in the wider Caribbean. Pages
35–68 in E. Rosenberg and Y. Loya, editors. Coral health
and disease. Springer-Verlag, Berlin, Germany.
Wilkinson, C. R. 2008. Status of coral reefs of the world: 2008.
Global Coral Reef Monitoring Network and Reef and
Rainforest Research Centre, Townsville, Australia.
Wilson, S. K., R. Fisher, M. S. Pratchett, N. A. J. Graham,
N. K. Dulvy, R. A. Turner, A. Cakacaka, and N. Polunin.
2010. Habitat degradation and fishing effects on the size
structure of coral reef fish communities. Ecological Applica-
tions 20:442–451.
Wilson, S. K., N. A. J. Graham, and N. V. C. Polunin. 2007.
Appraisal of visual assessments of habitat complexity and
benthic composition on coral reefs. Marine Biology
151:1069–1076.
Zar, J. H. 1999. Biostatistical analysis. Fourth edition. Prentice-
Hall, Upper Saddle River, New Jersey, USA.
September 2011 2231CORAL IDENTITY UNDERPINS REEF COMPLEXITY
... As such, the generally accepted, positive association between diversity and structural complexity may not be universal but more context specific. The type and dominance of key reef-building corals can be just as important as their overall abundance in maintaining reef structural complexity, as proposed by Alvarez-Filip et al. (2011). Below we discuss the findings in more detail and the implications for measuring structural complexity and for shoreline protection provided by coral reefs. ...
... A number of studies have also reported significant relationships between overall coral cover and structural complexity (Alvarez-Filip et al. 2011;Darling et al. 2017;Magel et al. 2019;Price et al. 2019;Carlot et al. 2020). In contrast to previous studies (Alvarez-Filip et al. 2011;Magel et al. 2019), we did not find a significant relationship between massive coral cover and any of the reef complexity metrics. ...
... A number of studies have also reported significant relationships between overall coral cover and structural complexity (Alvarez-Filip et al. 2011;Darling et al. 2017;Magel et al. 2019;Price et al. 2019;Carlot et al. 2020). In contrast to previous studies (Alvarez-Filip et al. 2011;Magel et al. 2019), we did not find a significant relationship between massive coral cover and any of the reef complexity metrics. The lack of a significant relationship may be related to the specific history and the massive coral assemblage at these sites. ...
Article
Full-text available
The three-dimensional (3D) structure of living coral communities provides frictional resistance to waves and currents. Coral bleaching events can lead to a shift in coral assemblages toward stress-tolerant colonies, potentially reducing reef structural complexity and, in turn, wave attenuation. This is a particular concern in low-lying coastal regions at risk from sea-level rise. In this study, we examined trade-offs between reef resilience and reef structural complexity (defined into three distinct variables, i.e., surface rugosity, standard deviation of elevation, and terrain ruggedness) in Kiribati’s Tarawa and Abaiang Atolls, which are subject to frequent El Niño-driven heat stress. Analysis of benthic cover data and 3D reconstructions of the fore reefs indicate that structural complexity increases with coral cover, rather than coral diversity, although the relationship depends on the metric used and on the morphology of the dominant coral species. Contrary to expectations, surface rugosity and standard deviation of elevation were not significantly different between the bleaching-resistant reefs of South Tarawa, dominated by the encrusting species Porites rus, and the more diverse sites in Abaiang and North Tarawa; terrain ruggedness was significantly greater at South Tarawa sites. A wave attenuation model, however, suggested that wave energy may nonetheless be higher in South Tarawa due to years of local mining of reef rock from the reef flat. Taken together, the results suggest that the survival of stress-tolerant corals could mitigate against losses of structural complexity from repeated bleaching events. These findings illustrate the need for more research bridging ecology and geology to establish how wave attenuation is altered by climate-driven regime shifts on coral reefs.
... Shifts in community composition and coral colony size structure can have cascading effects on ecosystem functioning, as large colonies often contribute disproportionally more to structural complexity and reproduction (Alvarez-Filip et al. 2011), while small colonies can disproportionally increase carbonate production in the short-term (Carlot et al. 2021). This also means that spatial differences in community structure may strongly determine recovery trajectories of reefs. ...
Article
Coral bleaching events and resultant changes in benthic community composition and population size structure can diminish the important geo‐ecological functions reefs provide, including habitat provision and carbonate production to support reef accretion. Net reef carbonate budgets, the balance between carbonate production and erosion processes, are thus important functional indicators of reef health. This study quantifies changes in coral community composition and colony size structures, and the resultant reef carbonate budget trajectories after the 2015/2016 bleaching event in the remote Chagos Archipelago, Indian Ocean. ReefBudget surveys were conducted at 12 sites across three atolls in 2015, 2018, and 2021, with calculations of biological carbonate production and erosion supported by locally obtained calcification and bioerosion rates. Carbonate budgets (in G = kg CaCO3 m−2 yr−1) shifted from net positive states in 2015 (mean ± SD: 3.8 ± 2.6 G) to net negative states in 2018 (−2.4 ± 1.4 G) in response to bleaching‐driven mass coral mortality. By 2021, all sites were on a trajectory of recovery, but net budgets differed significantly between atolls (−2.0 ± 1.7 to 2.2 ± 1.4 G). At Salomon atoll, the threefold faster recovery of carbonate production and return to positive reef budget states only 6 yr post‐bleaching was associated with the persistence of high structural complexity and the rapid recovery of fast growing tabular Acropora spp. Inter‐atoll differences in colony size distributions furthermore illustrate that coral identity and size class are more important predictors of reef functions and post‐disturbance recovery speed than coral cover alone.
... The expert panel proposed narrative rules for the BCG model expected high coral rugosity to indicate natural, high quality coral reef conditions and expected relative rugosity values to continue to decline with degraded coral reef conditions. Coral reef architectural complexity, measured as rugosity, has the capacity to provide the foundational taxa that highly influence the structure, function, and stability of the reef ecosystems (Alvarez-Filip et al., 2011). Alternatively, studies show decreases in coral reef condition and resilience are correlated with declines in rugosity values; increased anthropogenic stressors, including climate change, will cause greater reef degradation and coral mortality (Bozec et al., 2015). ...
Article
Full-text available
The Biological Condition Gradient (BCG) is a conceptual model used to describe incremental changes in biological condition along a gradient of increasing anthropogenic stress. As coral reefs collapse globally, scientists and managers are focused on how to sustain the crucial structure and functions, and the benefits that healthy coral reef ecosystems provide for many economies and societies. We developed a numeric (quantitative) BGC model for the coral reefs of Puerto Rico and the US Virgin Islands to transparently facilitate ecologically meaningful management decisions regarding these fragile resources. Here, reef conditions range from natural, undisturbed conditions to severely altered or degraded conditions. Numeric decision rules were developed by an expert panel for scleractinian corals and other benthic assemblages using multiple attributes to apply in shallow-water tropical fore reefs with depths <30 m. The numeric model employed decision rules based on metrics (e.g., % live coral cover, coral species richness, pollution-sensitive coral species, unproductive and sediment substrates, % cover by Orbicella spp.) used to assess coral reef condition. Model confirmation showed the numeric BCG model predicted the panel’s median site ratings for 84% of the sites used to calibrate the model and 89% of independent validation sites. The numeric BCG model is suitable for adaptive management applications and supports bioassessment and criteria development. It is a robust assessment tool that could be used to establish ecosystem condition that would aid resource managers in evaluating and communicating current or changing conditions, protect water and habitat quality in areas of high biological integrity, or develop restoration goals with stakeholders and other public beneficiaries.
... Reef complexity is important to many ecological patterns and processes, such as the maintenance of biodiversity (Torres-Pulliza et al. 2020), habitat zonation (Done 1982), and recovery following disturbances (Burns et al. 2016). While the importance of structural complexity has been recognized for decades (Alvarez-Filip et al. 2011;Graham and Nash 2013), little is known about how individual corals of different species, morphologies, and sizes contribute to reef complexity in an objective, quantitative manner. This knowledge gap exists because of past difficulties in measuring the three-dimensional (3D) complexity of large reef patches and the lack of standardized complexity metrics (Kovalenko et al. 2012). ...
Article
Full-text available
The structural complexity of coral reefs provides important ecosystem functions, such as wave attenuation for coastal protection, surfaces for coral growth, and habitat for other organisms. Corals build much of this structure, but an understanding of how colonies of different species and sizes contribute to complexity is lacking. We quantified three interdependent descriptors of complexity—rugosity, fractal dimension, and height range—for reef patches as well as the corals growing upon them in Kāne‘ohe Bay (O‘ahu, Hawai‘i). Despite similar levels of reef-scale complexity throughout the bay, we found marked differences in how species contribute to this complexity. Variation in complexity among species was closely tied to colony morphology, but not to colony size. Together, our results show that no one species is sufficient to generate the full spectrum of habitat complexities we see on coral reefs, which could have implications for reef recovery and restoration.
... However, hurricanes can diminish live coral cover from 15 to 60 per cent 105 and reef complexity in a few hours. 106 Ensuring the health of the Mesoamerican Reef, including having a well-managed network of protected areas in place, improves the physical and financial resilience of the area to climate-driven storms. Healthy reefs provide coastal protection, reduce damages to communities and tourism infrastructure and sustain businesses, jobs and livelihoods. ...
... However, hurricanes can diminish live coral cover from 15 to 60 per cent 105 and reef complexity in a few hours. 106 Ensuring the health of the Mesoamerican Reef, including having a well-managed network of protected areas in place, improves the physical and financial resilience of the area to climate-driven storms. Healthy reefs provide coastal protection, reduce damages to communities and tourism infrastructure and sustain businesses, jobs and livelihoods. ...
Article
Full-text available
Coral reefs ecosystems are facing an unprecedented decline due to the action of natural and anthropogenic stressors. The Caribbean Sea is considered to be one of the most impacted areas, as the average estimated scleractinian coral cover in this region decreased from approximately 50% to 10% over the last 30 years. In this study, a ten-year biodiversity survey was used to examine changes in abundance and percentage cover of benthic invertebrates on permanent transects located at four shallow coral reefs around Roatán, Honduras. This study represents the first long-term investigation of the coral ecosystem of Roatán and reports a decrease in scleractinian coral cover from 37.45 [± 5.37]% to 28.95 [± 3.62]% and a concomitant increase in macroalgal (7.02 [± 3.59]% to 13.94 [± 2.69]%) and turf (5.11[ ± 0.84]% to 7.23 [± 1.00]%) cover although no significant differences in the abundance of scleractinian corals, soft corals, or sponges were observed on the transects. While the four reef sites supported more variable benthic communities at the onset of the study, an overall homogenization of the benthic community composition occurred during the study period. Although our study sites were limited to a small region of Roatán’s southern coral reef system, these observations add to results from other Caribbean locations and provide insights into how Mesoamerican coral reefs have changed over the last decade.
Article
Full-text available
Understanding how emergent ecological assemblages have diverged from natural states is fundamental in predicting future functioning and services of ecosystems. Coral reefs are of particular concern due to their high susceptibility to anthropogenic stressors. Yet, little is known about their pre-disturbance ranges of natural states, and most reports of decline are based on a limited number of sites and high levels of uncertainty. Here, we used a novel approach to estimate the physical functionality of reefs across marine ecoregions based on habitat suitability and morpho-functional traits for coral species. We calibrated ecological niche models for 49 reef-building corals of the Greater Caribbean based on occurrence records and environmental predictors, which we combined with species-specific functional coefficients derived from morpho-functional traits reflecting their contribution to the reef three-dimensional structure to estimate the reef functional potential (RFP). We then assessed the degree of divergence of western Caribbean reefs by comparing our physical functionality estimates against recent field data evaluations. We found spatial variability in RFP across the Caribbean, with the highest mean value in the western Caribbean and the lowest in areas with marginal environmental conditions. Hotspots of RFP exist along the coast of Belize and the southeast of Cuba. Overall, 84% of sites along the western Caribbean showed a substantial reduction in their physical functioning, with the highest reductions occurring within hotspots, implying that reefs displaying the greatest changes have high initial RFP. We conclude that combining niche models with species morpho-functional traits is a valuable and promising approach to estimate the large-scale functional potential of communities and the degree of change in the absence of ecological baselines. These findings have important implications and could be used to guide efforts to preserve coral reefs functionality and define priority conservation areas in the Caribbean.
Article
Full-text available
As coral reef communities change and reorganise in response to increasing disturbances, there is a growing need for understanding species regimes and their contribution to ecosystem processes. Using a case study on coral reefs at the epicentre of tropical marine biodiversity (North Sulawesi, Indonesia), we explored how application of different biodiversity approaches (i.e., use of major taxonomic categories, high taxonomic resolution categories and trait-based approaches) affects the detection of distinct fish and benthic communities. Our results show that using major categories fails to identify distinct coral reef regimes. We also show that monitoring of only scleractinian coral communities is insufficient to detect different benthic regimes, especially communities dominated by non-coral organisms, and that all types of benthic organisms need to be considered. We have implemented the use of a trait-based approach to study the functional diversity of whole coral reef benthic assemblages, which allowed us to detect five different community regimes, only one of which was dominated by scleractinian corals. Furthermore, by the parallel study of benthic and fish communities we provide new insights into key processes and functions that might dominate or be compromised in the different community regimes.
Article
Full-text available
Coral cover has declined on reefs worldwide with particularly acute losses in the Caribbean. Despite our awareness of the broad-scale patterns and timing of Caribbean coral loss, there is little published information on: (1) finer-scale, subregional patterns over the last 35 yr, (2) regional-scale trends since 2001, and (3) macroalgal cover changes. We analyzed the spatiotemporal trends of benthic coral reef communities in the Caribbean using quantitative data from 3777 coral cover surveys of 1962 reefs from 1971 to 2006 and 2247 macroalgal cover surveys of 875 reefs from 1977 to 2006. A subset of 376 reefs was surveyed more than once (monitored). The largest 1 yr decline in coral cover occurred from 1980 to 1981, corresponding with the beginning of the Caribbean-wide Acropora spp. white band disease outbreak. Our results suggest that, regionally, coral cover has been relatively stable since this event (i.e. from 1982 to 2006). The largest increase in macroalgal cover was in 1986, 3 yr after the regional die-off of the urchin grazer Diadema antillarum began. Subsequently, macroalgal cover declined in 1987 and has been stable since then. Regional mean (±1 SE) macroalgal cover from 2001 to 2005 was 15.3 ± 0.4% (n = 1821 surveys). Caribbeanwide mean (±1 SE) coral cover was 16.0 ± 0.4% (n = 1547) for this same time period. Both macroalgal and coral cover varied significantly among subregions from 2001 to 2005, with the lowest coral cover in the Florida Keys and the highest coral cover in the Gulf of Mexico. Spatio-temporal patterns from the subset of monitored reefs are concordant with the conclusions drawn from the entire database. Our results suggest that coral and macroalgal cover on Caribbean reef benthic communities has changed relatively little since the mid-1980s.
Article
Beginning in the late 1980s, white-band disease nearly eliminated the staghorn coral Acropora cervicornis from reefs in the central shelf lagoon of Belize. The lettuce coral Agaricia tenuifolia replaced Acropora cervicornis in the early 1990s, but anomalously high water temperatures in 1998 caused severe bleaching and catastrophic mortality of Agaricia tenuifolia. The short-lived transition in dominance from Acropora cervicornis to Agaricia tenuifolia left an unambiguous signature in the fossil record of these uncemented lagoonal reefs. Analysis of 38 cores, extracted from 22 sampling stations in a 375-km2 area of the central lagoon, showed that Acropora cervicornis dominated continuously for at least 3000 years prior to the recent events. Agaricia tenuifolia occasionally grew in small patches, but no coral-to-coral replacement sequence occurred over the entire area until the late 1980s. Within a decade, the scale of species turnover increased from tens of square meters or less to hundreds of square kilometers or more. This unprecedented increase in the scale of turnover events is rooted in the accelerating pace of ecological change on coral reefs at the regional level.
Article
The ecological consequences of biodiversity loss have aroused considerable interest and controversy during the past decade. Major advances have been made in describing the relationship between species diversity and ecosystem processes, in identifying functionally important species, and in revealing underlying mechanisms. There is, however, uncertainty as to how results obtained in recent experiments scale up to landscape and regional levels and generalize across ecosystem types and processes. Larger numbers of species are probably needed to reduce temporal variability in ecosystem processes in changing environments. A major future challenge is to determine how biodiversity dynamics, ecosystem processes, and abiotic factors interact.
Article
There is increasing evidence that facilitative effects of various organisms can play important roles in community organization. However, on tropical coral reefs, where scleractinian corals have long been recognized as important foundation species creating habitat and resources that are utilized by a diversity of taxa, such relationships have rarely been studied and never within the contemporary theoretical context of facilitation. In the present study, we surveyed coral reefs on the south coast of St. John, US Virgin Islands, with the goal of quantifying the relationship between 'coral traits' (3 distinctive characteristics of scleractinian communities) and the abundance and diversity of benthic invertebrates associated with the reefs. We defined coral traits as coral diversity, percentage cover of live coral, and the topographic complexity created by coral skeletons, and statistically evaluated their roles in accounting for the abundance and diversity of conspicuous invertebrates at 25 sites. The analysis yielded contrasting results in terms of the putative facilitative roles of scleractinian corals. Coral traits were significantly and positively related to the diversity of reef-associated invertebrates, but were not related to invertebrate abundance. Topographic complexity (but not coral cover) had relatively strong explanatory ability in accounting for the variation in invertebrate diversity, although a substantial fraction of the variance in invertebrate diversity (45%) remained unexplained. While these results are correlative, they demonstrate that a statistical majority of the variation in the diversity of conspicuous invertebrates on Caribbean reefs can be explained by the role of coral skeletons in creating topographic relief with diverse morphologies, although processes independent of coral traits also play important roles. In an era of globally declining coral cover, these findings suggest that the progressive loss of coral skeletons from tropical reefs will lead to substantial losses of invertebrate diversity that might initially be obscured by conserved abundances.
Article
Wave measurements during three experiments at Tague Reef, St. Croix (U.S.V.I.) in April 1987 showed a net energy decrease across the reef profile of 65-71% between the forereef and crest, wave propagation to the backreef increased energy reduction to 78-88%. Tidally induced water depth changes (range of 0.3 m) increased wave energy dissipation by 15% between forereef and crest and 20% between forereef and backreef. Significant wave heights throughout the experiment were low (< 0.5 m) and exhibited a tidal modulation in the backreef or lagoon. Wave transmission over the reef averaged 0.46 and modulated by the tide (0.32 at low tide vs 0.62 at high tide). The spectral time-delay model applied to analyzed wave transformations across the reef produced attenuation coefficients that averaged 0.62 between 0.05 and 0.1 cps (20-10 s) and afterwards oscillate between 0.22 and 0.35. For waves between the forereef and backreef, the attenuation coefficients from the time-delay model decay exponentially between 0.05 and 0.1 cps, afterwards they oscillate between 0.13 and 0.2. The steady wave-energy model with bottom friction, essentially form drag, and wave breaking dissipation yield wave heights modulated by the tides and errors of < 19% in the crest and > 20% at the backreef. The model revealed that while frictional and wave-breaking dissipation are equally important, frictional dissipation is greater.