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Regional spatio-temporal trends in Caribbean coral reef benthic communities


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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.
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Mar Ecol Prog Ser
Vol. 402: 115122, 2010
doi: 10.3354/meps08438
Published March 8
Based on a recently published global map of the
magnitude and geographic extent of 17 anthropogenic
threats, Halpern et al. (2008) argued that coral reefs
are one of the world’s most heavily impacted marine
ecosystems. This finding is consistent with a vast body
of literature documenting the global degradation of
tropical reefs over the last several decades (Wilkinson
1992, Grigg 1994, Gardner et al. 2003, Bruno & Selig
2007, Edmunds & Elahi 2007). Coral loss can lead to
reductions in fish abundance and diversity (Jones et al.
2004, Pratchett et al. 2008) and declines in topographi-
cal complexity (Alvarez-Filip et al. 2009). Coral loss is
also associated with compensatory increases in the
abundance of several other taxa, including sponges,
© Inter-Research 2010 ·*Email:
Regional spatio-temporal trends in Caribbean
coral reef benthic communities
Virginia G. W. Schutte
1, 3,
, Elizabeth R. Selig
1, 2, 4
, John F. Bruno
Department of Marine Sciences, The University of North Carolina at Chapel Hill, 340 Chapman Hall CB# 3300, Chapel Hill,
North Carolina 27599-3300, USA
Curriculum for the Environment and Ecology, 207 Coastes Building CB# 3275, The University of North Carolina at Chapel
Hill, Chapel Hill, North Carolina 27599-3275, USA
Present address: Odum School of Ecology, The University of Georgia, 140 E. Green St., Athens, Georgia 30602-2202, USA
Present address: Center for Applied Biodiversity Science, Conservation International, 2011 Crystal Drive, Suite 500,
Arlington, Virginia 22202, USA
ABSTRACT: 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 spatio-
temporal 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). Caribbean-
wide 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.
KEY WORDS: Coral cover · Macroalgae · Coral disease · Coral bleaching
Resale or republication not permitted without written consent of the publisher
Mar Ecol Prog Ser 402: 115122, 2010
gorgonians, and macroalgae (Hughes 1994, Aronson et
al. 2002, Norström et al. 2009). A wide variety of causes
and human activities have been implicated in driving
these changes, including overfishing,
increasing ocean temperatures, coral
disease and predator outbreaks, and
poor land-use practices that lead to sed-
imentation and nutrient pollution
(Endean 1977, Jackson et al. 2001,
Hughes et al. 2003, Fabricius 2005,
Hoegh-Guldberg et al. 2007).
Although the key drivers of coral loss
have been identified, there is no con-
sensus on their relative importance and
how this varies in space and time
(Grigg & Dollar 2005, Precht et al.
2005). Quantifying the spatio-temporal
changes in coral reef benthic communi-
ties at regional and decadal scales can
lead to a broader understanding of the
patterns and causes of reef degradation
and provide information which will
result in more effective management
actions (Côté et al. 2005).
The purpose of the present study was
to quantify the regional-scale trends in
coral and macroalgal cover on Carib-
bean coral reefs over the last 35 yr in
each of 7 subregions (Fig. 1A). Our
study builds on previous analyses of
benthic changes on particular reefs
(Edmunds & Elahi 2007), whole islands
(Hughes 1994), and a meta-analysis of
the entire region (Gardner et al. 2003).
Although the broad-scale patterns and
timing of Caribbean coral loss were dis-
cussed in Gardner et al. (2003), there is
no published information on regional-
scale trends for macroalgal cover or for
coral cover since 2001. Our analysis
was based on data from 3777 surveys of
1962 reefs performed between 1971
and 2006 the largest compilation of
quantitative Caribbean reef surveys to
All analyses were based on quantita-
tive in situ surveys of subtidal coral
reefs in the Caribbean basin that mea-
sured the percentage of the bottom cov-
ered by living scleractinian coral tissue.
We grouped these survey sites into 7
subregions, which were similar to previous delineation
schemes and were based on areas of similar biodiver-
sity and biogeography, major bathymetric changes, or
Fig. 1. (A) Locations of survey sites (purple dots; n = 1667) and delineations of the 7
subregions used in our analyses. The 295 sites for which we could not obtain ex-
act coordinates are not shown. (B) Number of thermal stress anomalies during
2005. Sea surface temperature data were derived from the Advanced Very High
Resolution Radiometer sensor and were processed to a resolution of approxi-
mately 4.6 km at the equator. An anomaly is defined as 1°C more than the typical
maximum climatological week defined for each grid cell (see also Text S3 in the
supplement, pdf)
Schutte et al.: Caribbean reef trends
management regimes (Fig. 1A; Spalding et al. 2007).
The coral and macroalgal cover survey database was
compiled by searching the scientific literature using a
variety of search engines (e.g. ISI Web of Science and
Google Scholar) using terms including ‘Caribbean’
and ‘coral cover’. We also examined every issue of
Coral Reefs, Atoll Research Bulletin, the Proceedings
of the Colloquium on Global Aspects of Coral Reefs
(Ginsburg 1993), and the Proceedings of the Interna-
tional Coral Reef Symposiums. When cover data were
presented in graphical form, we used ImageJ (Rasband
2006) to extract the raw data (the percent cover). In
addition, we obtained survey data directly from sev-
eral monitoring programs (Text S1, Fig. S1 & Table S1
in the supplement,
m402p115_app.pdf), including the Florida Coral Reef
Evaluation and Monitoring Project (CREMP; data com-
prise 35.6% of surveys and 13.1% of sites), the Atlantic
and Gulf Rapid Reef Assessment (AGRRA) Program
(17.1% of surveys and 30.3% of sites), and Reef Check
(16.5% of surveys and 22.8% of sites).
The database included 3777 coral cover surveys from
1962 sites surveyed between 1971 and 2006 (Text S1 &
Table S2 in the supplement,
suppl/m402p115_app.pdf). We pooled observations
across depths (1 to 30 m depth, 8.2 ± 0.08 m, mean ±
1 SE; Fig. S2 in the supplement,
articles/suppl/m402p115_app.pdf) and reef zones for
our analyses because there was little variation in sur-
vey depth among subregions or years and there was
no relationship between depth and cover (Text S2 &
Fig. S3 in the supplement,
suppl/m402p115_app.pdf). The cover of Millepora spp.
(hydrozoans) was included in the total live coral cover
value for 181 surveys (4.1% of all surveys). Macroalgal
cover, including both fleshy and calcifying macroalgae
(sensu Steneck 1988), was measured in 2247 surveys
on 875 reefs (58.4 and 44.6% of the total, respectively).
We did not include cover from turf or coralline encrust-
ing algae. In 64.6% of surveys, benthic cover was mea-
sured in situ using related techniques such as the
AGRRA Program methodology (Lang 2003) and point
intercept cover estimates (Hodgson et al. 2006, Lam et
al. 2006). For the other 35.4%, the substrate was re-
corded with video or still photographs (Edmunds &
Bruno 1996), which were analyzed in the laboratory
using image analysis software or the point count tech-
nique (Aronson et al. 2002, Idjadi & Edmunds 2006,
Lam et al. 2006, Rogers & Miller 2006).
Annual sample sizes for the whole region (~200 to
400 surveys; Fig. 2) and for many subregions (Table S1)
over the last decade are quite large, and most survey
sites were more or less randomly or haphazardly se-
lected (particularly with respect to the hypotheses being
tested in this analysis). In other words, we used survey
data regardless of the original research purpose. There-
fore, our analyses are likely representative of the broad-
scale trends on benthic reef communities, particularly
since the mid-1990s. Yet meta-analyses of field surveys
such as this have a number of limitations, and several
caveats need to be considered when interpreting the re-
sults (Bruno & Selig 2007). First, year-to-year variations
in which sites are sampled can cause apparent short-
term temporal trends that are likely sampling artifacts
and not real phenomena. As in any long-term analysis,
short-term and temporary fluctuations are expected,
may not be real, and should not be over-interpreted.
Second, for a variety of reasons, some sites and sub-
regions have been sampled far more intensively than
others. We used a repeated measures linear regression
analysis to test the null hypothesis that there was
no relationship between percent coral or macroalgal
cover and time (using Stata Version 9.1, STATA). This
test was based on the individual trajectories of the 7
subregions rather than pooled data for each year. Per-
forming this analysis on yearly subregional averages
equalizes the influence of each subregion. However, it
does not remove the influence of highly sampled sites
on subregional values. Additionally, some important
locations were sampled comparatively sparsely rela-
tive to their size, e.g. Belize. Therefore, the regional
and subregional trends may not be representative of
all parts of the Caribbean. Our general trends also
might differ from the true, but unknowable, population
values. The population-level trends we quantified are
not meant to represent the trajectory of any individual
reef. Additionally, trends from the early years of the
database should be interpreted with great caution
given their relatively small annual sample sizes. We
still know very little about the natural baselines of
Caribbean reefs and even less about their state even in
the near-past, e.g. the 1960s. Thus, putting our results
into a broader historical context is very difficult. It is
possible that Caribbean reefs began to degrade long
before we began surveying them (Pandolfi et al. 2003),
in which case the actual degree of degradation is much
greater than we can currently quantify.
The database largely consisted of reefs surveyed only
once, but included 376 reefs surveyed in 2 or more
years. We analyzed this subset of monitored reefs sepa-
rately from the entire database, restricting the analysis
to surveys performed between 1996 and 2006 (n = 331
reefs; Table S3 in the supplement,
journals/articles/m402p115_app.pdf), because few
reefs were monitored before this time period. Re-
peated-measures regression analysis was used to de-
termine whether coral or macroalgal cover changed
significantly from 1996 to 2006. We performed separate
analyses for each subregion and also an analysis of all
the monitoring data combined.
Mar Ecol Prog Ser 402: 115122, 2010
Regional temporal trends
Numerous studies indicate that Caribbean reef ben-
thic communities changed dramatically in the 1980s
(Hughes et al. 1985, Carpenter 1990, Liddell & Ohl-
horst 1992, Hughes 1994, Gardner et al. 2003). Despite
the general perception that Caribbean reefs have con-
tinued to degrade, the broad-scale cover of hard corals
and macroalgae appears to have changed very little
since at least the mid-1980s. Our analysis suggests that
the regional coral cover average has not changed sig-
nificantly since the 1981 Acropora spp. mass mortality
(i.e. from 1982 to 2006, p = 0.99, based on repeated-
measures regression of annual subregional means;
Fig. 2A). This pattern of regional stasis does not contra-
dict studies that have documented recent, i.e. post-
1980s, coral loss on individual reefs (e.g. Aronson et
al. 2002, Edmunds 2007) and in some subregions such
as the Florida Keys (Fig. S4 in the supplement, www.; Porter &
Meier 1992, Maliao et al. 2008). Instead it suggests that
local losses on some reefs have apparently been
roughly balanced by local coral recovery on other
reefs. In other words, the observed pattern of regional
stasis is probably a dynamic equilibrium, masking
greater spatio-temporal variance in benthic commu-
nity structure at finer spatial scales. Additionally,
because we were only able to analyze broad-scale pat-
terns in total coral and macroalgal cover, we could not
evaluate other reef characteristics such as trophic com-
plexity (Paddack et al. 2009), reef rugosity (Alvarez-
Filip et al. 2009), or changes in species composition
(e.g. Aronson et al. 2004), which may indeed have
changed during the study period and are also impor-
tant indicators of coral reef health.
Disturbances before the mid-1980s caused substan-
tial regional losses in coral cover. Caribbean-wide
coral cover averages were highest from 1971 to 1980
(Fig. 2A). Annual regional means during this period
ranged from ~25 to 40% (n = 43 surveys), which is
somewhat lower than generally assumed (Gardner et
al. 2003). Our results suggest that regional absolute
coral cover declined by ~18% between 1972, the year
with the highest yearly coral cover mean (38.3%, n = 1
1970 1975 1980 1985 1990 1995 2000 2005 1970 1975 1980 1985 1990 1995 2000 2005
A) Coral B) Macroalgae
D) FLK coralC) Coral-no FLK
Cover (%)
No. of studies
Fig. 2. Annual cover values (±1 SE, closed circles, left y-axis) and site sample sizes (open circles, right y-axis) for (A) mean coral
cover for all sites in the Caribbean basin (n = 1962; star: 1980, the year in which Hurricane Allen struck and white band disease
outbreaks began); (B) mean macroalgal cover for all sites for which data were available (n = 875; star: 1983, the year in which the
Diadema antillarum die-off began); (C) mean coral cover for all sites in the greater Caribbean except those in the Florida Keys
(FLK; n = 1515); and (D) mean coral cover for all sites in the FLK subregion (n = 447)
Schutte et al.: Caribbean reef trends
survey), and 1982 (20.8 ± 4.2%, n = 7 surveys), when
the current period of regional stasis began (Fig. 2A).
However, the annual coral cover means during this
period are based on a small number of surveys
(Table S2) and it is possible that the historical regional
baseline was higher. The largest 1 yr decline in coral
cover (24.9 ± 3.2% absolute coverage) took place from
1980 to 1981, coincident with and presumably due to
the regional Acropora spp. die-off from the white band
disease epizootic (Aronson & Precht 2001, 2006) and
the passage of Hurricane Allen through Jamaica
(Woodley et al. 1981), where 9 of the 21 surveys con-
ducted in 1980 and 1981 were performed.
Just over half of the coral cover surveys had accom-
panying macroalgal cover values; our database inclu-
ded 2247 macroalgal surveys conducted between 1977
and 2006. Macroalgal cover did not change between
1987 and 2006 (p = 0.13; Fig. 2B), although the small
number of quantitative surveys in the 1980s and early
1990s makes estimates of subregion-specific macroal-
gal trends during this period less reliable (Table S2). It
is possible that some other rarely measured attribute of
macroalgae changed during the period of stasis, e.g.
biomass, height, or composition, although macroalgal
cover is generally a good predictor of macroalgal bio-
mass (Miller et al. 2003).
The regional mean coverage of macroalgae increa-
sed dramatically in 1986 (26.0 ± 13.3%; Fig. 2B) follow-
ing the Caribbean-wide die-off of the sea urchin Dia-
dema antillarum in 1983 and 1984 (Hughes et al. 1985,
Lessios 1988). Mean macroalgal cover before the D.
antillarum die-off (based on 37 surveys performed
from 1977 to 1983) was 8.0 ± 1.6%. In 1986, macroalgal
cover increased to 38.1 ± 13.3% (n = 8 surveys). How-
ever, it declined again to 14.5% in 1987 (± 5.7, n = 13
surveys) and the regional mean remained below 20%
for most years between 1987 and 2006. The drop in
macroalgal cover following the spike in 1986 could be
due to compensatory population increases or behav-
ioral responses by other fish and urchin grazers to the
loss of the once dominant herbivore, D. antillarum
(Aronson et al. 2000, Haley & Solandt 2001). Popula-
tions of D. antillarum have since recovered on some
Caribbean reefs (e.g. Carpenter & Edmunds 2006,
Myhre & Acevedo-Gutiérrez 2007), which could ex-
plain the general absence of macroalgal cover changes
since 1987. Conversely, the 1986 spike in macroalgal
cover could be an artifact of non-random site selection;
many macroalgal cover studies conducted in the mid-
1980s focused on reefs that experienced significant
losses in coral cover or were designed to document the
indirect effects of the D. antillarum die-off (e.g.
Hughes 1994).
The combined multi-decade, regional patterns of
changes in coral and macroalgal cover indicate that,
although the region has experienced substantial coral
losses, there has not been a concomitant increase in
macroalgal cover (Fig. 3). Almost half (48.9%) of the
2247 macroalgal surveys documented a higher percen-
tage of macroalgal cover than coral cover, but macroal-
gal cover has rarely exceeded 50% (just 5.2% of sur-
veys). The observed regional increase in macroalgal
cover in 1986 occurred 5 yr after the collapse of coral
cover in 1981, supporting the argument that coral loss
in the 1980s was not caused by an increase in macro-
algal cover (Aronson & Precht 2006, Bruno et al. 2009).
The relationship between coral and macroalgal
cover on reefs over time can be divided into 3 temporal
categories (Fig. 3): (1) the late 1970s, the baseline for
the present study; (2) the 1980s and early 1990s, after
the Acropora spp. and Diadema antillarum disease
outbreaks; and (3) from 1993 to 2006, a period of post-
disease stability. We pooled the annual means within
each temporal period in order to compare the 3 peri-
ods, and the greatest coral cover loss occurred from
Time Period 1 to Time Period 2. There was not a long-
term increase in macroalgal cover proportional to the
coral cover loss in the 1980s.
Recent spatial patterns
Recent (2001 to 2005) macroalgal cover varied signi-
ficantly among subregions (ANOVA, p < 0.0001; Fig. 4)
and ranged from 6.2 ± 4.0% (n = 16 surveys) in the Gulf
of Mexico to 22.8 ± 1.6% (n = 100 surveys) in the south-
Fig. 3. Average annual coral and macroalgal cover values
from 1977 to 2006. Horizontal and vertical lines represent
1 SE. The 3 points from the 1981 to 1992 group that are
clumped with the 1993 to 2006 values are from 1981, 1987,
and 1988
Mar Ecol Prog Ser 402: 115122, 2010
western Caribbean. The region-wide mean cover of
macroalgae from 2001 to 2005 was 15.3 ± 0.4% (n =
1821 surveys), while mean coral cover was 16.0 ± 0.4%
(n = 1547 surveys). Recent coral cover also varied sig-
nificantly among subregions (ANOVA, p < 0.0001;
Fig. 4; see also Fig. S4). Subregional coral cover dif-
ferences are concordant with a previous analysis of the
Caribbean (Gardner et al. 2003). Assuming the histori-
cal coral cover baseline was similar across the region,
this pattern of current spatial variability could be inter-
preted as evidence of variable rates of coral loss.
Recent coral cover was highest in the Gulf of Mexico
(58.1 ± 3.5% from 2001 to 2005, n = 10 surveys). The
high cover in this subregion was likely due to the
absence of Acropora spp. host populations in the
Flower Garden Banks (until recently; Precht & Aron-
son 2004), where most of the surveys from the Gulf of
Mexico were conducted, which precluded white band
disease from reducing Acropora spp. coral cover there
(Aronson et al. 2005). The Flower Garden Banks reefs
are also atypical sites because survey depths there
were from 20 to 30 m (e.g. Dokken et al. 2003), more
than twice the mean depth of most surveys in the
Recent coral cover was lowest in the Florida Keys
(FLK; 8.6 ± 0.4% from 2001 to 2005, n = 747 surveys).
This subregion was extensively sampled (50.6% of all
surveys performed from 1996 to 2006 were conducted
in the FLK; Table S2) and this overrepresentation
could have unduly influenced the Caribbean-wide
analyses. Therefore, we also analyzed the trends from
1996 to 2005 in regional coral and macroalgal cover
without the FLK data. This resulted in annual regional
coral cover means as much as 13.1% higher than when
the FLK data were included (Fig. 2C,D), but did not
noticeably influence macroalgal cover values. Mean
regional Caribbean coral cover without the FLK data
from 1996 to 2005 was 21.8 ± 0.3%.
The southeastern Caribbean experienced a severe
warming event in late 2005, with levels of thermal
stress exceeding standard bleaching thresholds
(Fig. 1B; Donner et al. 2007, Wilkinson & Souter 2008).
This led to widespread coral bleaching, subsequent
coral disease outbreaks, and moderate to severe local
coral mortality and loss in some locations, including
the US Virgin Islands and the Lesser Antilles (Miller
et al. 2006, Wilkinson & Souter 2008). There was a mi-
nor regional reduction in coral cover in 2006 (Fig. 2C),
which could have been caused in part by coral mortal-
ity in several subregions, particularly those that expe-
rienced the most severe temperature anomalies (Fig. 1;
see also Fig. S4), e.g. the Northern Caribbean (–6.0%
absolute cover from 2005 to 2006) and the Lesser An-
tilles (–3.8% absolute cover). However, we did not
have enough post-bleaching event data to reliably es-
timate subregional declines since 2005 (Table S2).
Monitored sites
Our analysis was primarily based on reefs that were
randomly selected and surveyed only once. The results
of such randomized population sampling can be gener-
alized to a greater degree than those from longitudinal
monitoring studies. However, randomized sampling
has some drawbacks, including sensitivity to sample
composition. Minor, short-term fluctuations in coral
and macroalgal cover (Fig. 2; see also Fig S4) could be
due to the subpopulation of reefs that were surveyed in
a given year, rather than to real year-to-year changes
in community state. Although non-random initial site
selection can cause similar biases, monitoring studies
are generally less sensitive to sample composi-
tion and have several advantages, including
greater power to detect small changes in com-
munity state. Unfortunately, there are still rela-
tively few quantitative reef monitoring pro-
grams and most are focused on well-studied
reefs within Marine Protected Areas.
Spatio-temporal patterns from the subset of
376 monitored reefs are very similar to those
from the entire database (Fig. S5 in the sup-
p115_app.pdf) and are concordant with our
general conclusions. The regional trends from
the sites monitored from 1996 to 2006 indicate
that, since 1996, there has been very little tem-
poral variation in both coral (n = 331) and
macroalgal cover (n = 215) and the trends rein-
force the finding that reefs in the Caribbean
entered a period of general regional stasis in
Fig. 4. Recent (2001 to 2005) macroalgal and coral cover in the 7
Caribbean subregions (Fig. 1). Values are means (+1 SE) and sample
sizes (no. of sites) are shown to the right of the bars. Mesoam Reef:
Mesoamerican Reef; N Caribbean: Northern Caribbean; SW Carib-
bean: Southwestern Caribbean
Schutte et al.: Caribbean reef trends
the mid-1990s, at least in terms of coral and macroalgal
cover. Linear repeated-measures regression analyses
indicate that there was no significant change in coral
cover (p = 0.32, n = 331 reefs) or macroalgal cover
(p = 0.109, n = 215 reefs) from 1996 to 2006 across the
region (Table S4 in the supplement,
articles/suppl/m402p115_app.pdf). We also analyzed
monitoring data from each subregion independently
from 1996 to 2006; in most cases, there was no sig-
nificant change in cover (Tables S5 & S6 in the supple-
pdf. There was a statistically, although perhaps not
ecologically, significant decrease in both coral and
macroalgal cover in the intensively monitored Florida
Keys. Coral cover slightly increased in the Northern
Caribbean and decreased in the Lesser Antilles and
the Southwestern Caribbean. Otherwise, our regres-
sion analyses of the monitoring data suggest that there
have been few other signs of temporal change within
subregions since 1996.
The first meta-analysis of Caribbean hard coral cover
documented a reduction from ~50% in 1977 to ~10%
in 2001 (Gardner et al. 2003). Our study built on that
work by adding surveys from an additional 1699 sites
and macroalgal data and by expanding the analysis to
2006. The timing of coral loss we documented is consis-
tent with the hypothesis that the acroporid white band
epizootic was the primary cause of hard coral cover
loss in the Caribbean (Aronson & Precht 2006). Like-
wise, the regional macroalgal bloom that occurred sev-
eral years after the disease-induced Diadema antil-
larum die-off supports the argument that a reduction
in herbivory, rather than increased nutrient availabil-
ity, caused the observed increases in macroalgal cover
(Hughes et al. 1999). Therefore, disease, whether nat-
ural or exacerbated by human activities, appears to
have been the primary driver of regional-scale
changes in Caribbean reef benthic communities over
the last 35 yr. Our results indicate that, since these 2
major disturbances, regional coral and macroalgal
benthic coverage has been relatively stable. However,
the future of Caribbean reefs is uncertain. There are
many factors besides disease that could cause fur-
ther changes in reef benthic community structure,
including climate change, ocean acidification, and
direct anthropogenic stressors like overfishing and
nutrient pollution (Hughes et al. 2003). Although our
results could be interpreted as relatively good news,
the observed regional pattern could also be a tempo-
rary plateau preceding a potential collapse in coral
Acknowledgements. We thank K. France, R. Katz, L. Ladwig,
S. C. Lee, M. I. O’Connor, C. Shields, G. Smelick, I. Vu, and
A. M. Melendy for assistance with this project, and J. C. Lang,
G. Hodgson, W. F. Precht, and W. K. Fitt for very helpful com-
ments on this paper. We are especially grateful to everyone
who shared data with us, including Reef Check, AGRRA,
Florida CREMP, the scientists and data managers who com-
municated with us personally, and all the volunteers and
researchers who collected the data. This project was funded
in part by the National Science Foundation, an Environmen-
tal Protection Agency STAR fellowship to E.R.S., and the Uni-
versity of North Carolina at Chapel Hill.
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Proofs received from author(s): February 18, 2010
... In this respect, our results are consistent with previous studies. For example, the long history of declining hard coral cover in the Western Atlantic, especially in the Caribbean, is well established in the literature [26][27][28] . Our results suggest that the declines documented in earlier studies in this realm 26,27 have continued, with the low levels of 10-15% coral cover in our study aligning well with recent reports 29 . ...
... For example, the long history of declining hard coral cover in the Western Atlantic, especially in the Caribbean, is well established in the literature [26][27][28] . Our results suggest that the declines documented in earlier studies in this realm 26,27 have continued, with the low levels of 10-15% coral cover in our study aligning well with recent reports 29 . Moreover, the relative stability of hard coral cover during this period in the Indo-West Pacific 30 as well as in the Indian Ocean (with the notable exception of the 1998 bleaching event) 31 , has been previously documented, with our levels of 25-30% also aligning well with recent reports from these regions 29 . ...
... Nevertheless, our study differs from these past studies as we separated algal forms and highlight that increasing cover of tall macroalgae is largely restricted to the Western Atlantic, with ramifications for how we perceive coral reef change globally. However, it is important to highlight that our study, along with the previous studies, represents realm-wide average trends, with changes within specific locations potentially diverging from these trajectories 27,29 . Importantly, we also explored how benthic trajectories varied in reef crest and slope habitats within realms. ...
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Globally, ecosystems are being reconfigured by a range of intensifying human-induced stressors. Coral reefs are at the forefront of this environmental transformation, and if we are to secure their key ecosystem functions and services, it is important to understand the likely configuration of future reefs. However, the composition and trajectory of global coral reef benthic communities is currently unclear. Here our global dataset of 24,468 observations spanning 22 years (1997-2018) revealed that particularly marked declines in coral cover occurred in the Western Atlantic and Central Pacific. The data also suggest that high macroalgal cover, widely regarded as the major degraded state on coral reefs, is a phenomenon largely restricted to the Western Atlantic. At a global scale, the raw data suggest decreased average (± standard error of the mean) hard coral cover from 36 ± 1.4% to 19 ± 0.4% (during a period delineated by the first global coral bleaching event (1998) until the end of the most recent event (2017)) was largely associated with increased low-lying algal cover such as algal turfs and crustose coralline algae. Enhanced understanding of reef change, typified by decreased hard coral cover and increased cover of low-lying algal communities, will be key to managing Anthropocene coral reefs.
... We found that total living coral cover has steadily declined ( Fig. 2B) since prior regional assessments [27][28][29] which suggested that coral loss may have plateaued by the late 1990s, at a regional mean of ~ 16%. However, our results indicate that from 1997 to 2017, the median annual loss rate was ~ 0.25% per year, with a final year regional mean of 9.5% ± 0.59% (SE). ...
... Supplementary Table S1. This study combined a previous version of a Caribbean coral cover database used for analysis in Selig and Bruno 72 and Schutte et al. 27 ) with more recent coral survey data from longitudinal studies and monitoring datasets. We relied heavily on data from monitoring programs because they provide large amounts of repeated measurements over long time frames and cover broad spatial scales, both of which are essential for making conclusions regarding regional trends and possibly help mitigate the effects of publication bias. ...
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Anthropogenic climate change is intensifying natural disturbance regimes, which negatively affects some species, while benefiting others. This could alter the trait composition of ecological communities and influence resilience to disturbance. We investigated how the frequency and intensification of the regional storm regime (and likely other disturbances) is altering coral species composition and in turn resistance and recovery. We developed regional databases of coral cover and composition (3144 reef locations from 1970 to 2017) and of the path and strength of cyclonic storms in the region (including 10,058 unique storm-reef intersections). We found that total living coral cover declined steadily through 2017 (the median annual loss rate was ~ 0.25% per year). Our results also indicate that despite the observed increase in the intensity of Atlantic cyclonic storms, their effect on coral cover has decreased markedly. This could be due in part to selection for disturbance-resistant taxa in response to the intensifying disturbance regime. We found that storms accelerated the loss of threatened acroporid corals but had no measurable effect on the cover of more resilient “weedy” corals, thereby increasing their relative cover. Although resistance to disturbance has increased, recovery rates have slowed due to the dominance of small, slow-growing species. This feedback loop is locking coral communities into a low-functioning state dominated by weedy species with limited ecological or societal value.
... Additionally, there are no obligate corallivores that rely on corals as a major part of their diet in the Caribbean (Burkepile 2012). Indeed, current fish assemblages may already reflect a response to the near-single-digit coral cover recorded in the Florida Keys since the early 1980s (Schutte et al. 2010). However, the variation of coral cover captured in the data (0-55%) suggests that the patterns described here are not simply artifacts of current reef state. ...
Anthropogenic stressors are causing widespread coral mortality, leading to loss of coral cover and decreased structural complexity that threatens reef biodiversity, functioning, and ecosystem services. Reef fishes are intimately linked to coral reef complexity, but we lack a generic understanding of which species are particularly affected by reef flattening and what traits make them susceptible. We used extensive species‐ and trait‐based analyses to build a framework for western Atlantic fish association with both structural complexity and coral cover to better understand the implications of reef degradation. These analyses also highlighted the relative importance of live coral versus the structure it provides to reef fishes, which currently remains unclear. We modeled how 25 biophysical and anthropogenic factors correlated with the densities of 109 fish species across 3292 Floridian reef sites. The importance of a metric of structural complexity and coral cover to the abundance of each species was then isolated. Species with positive associations were categorized as likely future ‘losers' and negative associations as ‘winners'. We predicted that 53% of species will be losers on low‐relief reefs, while only 11% were losers with decreased coral cover. We found morphological, behavioral, and ecological traits, not phylogeny, mediate species' responses to reef degradation and that the loss of structure seemed more critical than the loss of coral cover. Eight traits explained 79.7% of the variation in species' associations with relief and six traits explained 27.8% of associations with coral cover. Smaller, streamlined, habitat and trophic generalists are more likely winners on flattened reefs and large‐bodied predators, among other taxa, are likely losers of reef flattening. Identifying these important traits provides insight into mechanisms that may link fish and complex habitats, which allows us to better predict assemblage‐wide responses to future reef flattening.
... The Yucatan Peninsula is home to two primary reef systems: the Mesoamerican reef system that accounts for 153 predominantly barrier and fringing reefs (Santander-Monsalvo et al., 2018) and those of the Campeche and Yucatan Banks that comprise patchy reefs and submerged banks that extends up to 200 km from the coastline (Palomino-Alvarez et al., 2021). Studies have shown that the health of most shallow-water coral reefs along the coast from Texas to Florida is not good, and the coral reefs along the coast of Mexico have a low ability tolerate to thermal stress (Schutte et al., 2010;Somerfield et al., 2008). Therefore, it is expected that the temperature in the GoM will be a very big challenge for coral survival by the end of the 21st century (Dee et al., 2019;Holstein et al., 2022). ...
... Within the Great Barrier Reef, long-term monitoring revealed high recent declines and differing trajectories of coral and macroalgal cover on reefs across different continental shelf zones 25,26 , with a recent report reporting dramatic coral recovery 27 . The Caribbean monitoring programs produced clear evidence for the region-wide phase shift from coral to macroalgal cover, later revealed to have resulted from a myriad of interplaying factors including parrotfish and sea urchin declines [28][29][30] . In comparison, long-term monitoring studies are more limited and have not been as coordinated among the reefs in the Northeast and Southeast Asia regions, typically with Reef Check initiatives, national or non-governmental organisations and academic institutions running distinct programs 16 . ...
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Coral reefs in the Central Indo-Pacific region comprise some of the most diverse and yet threatened marine habitats. While reef monitoring has grown throughout the region in recent years, studies of coral reef benthic cover remain limited in spatial and temporal scales. Here, we analysed 24,365 reef surveys performed over 37 years at 1972 sites throughout East Asia by the Global Coral Reef Monitoring Network using Bayesian approaches. Our results show that overall coral cover at surveyed reefs has not declined as suggested in previous studies and compared to reef regions like the Caribbean. Concurrently, macroalgal cover has not increased, with no indications of phase shifts from coral to macroalgal dominance on reefs. Yet, models incorporating socio-economic and environmental variables reveal negative associations of coral cover with coastal urbanisation and sea surface temperature. The diversity of reef assemblages may have mitigated cover declines thus far, but climate change could threaten reef resilience. We recommend prioritisation of regionally coordinated, locally collaborative long-term studies for better contextualisation of monitoring data and analyses, which are essential for achieving reef conservation goals.
... When multiple impacts are in place, measuring the causes of coral cover reductions and predicting the trajectories of dominant taxa on tropical reefs is a complex task, and it is still a matter of debate how extensive and persistent the macroalgal dominance is (see Jackson et al. 2014 andPrecht et al. 2020 for opposing views of the Caribbean region). Nevertheless, the loss of coral cover is a worldwide trend that has risen in recent decades; estimates are that corals currently cover about 50−75% less of the substrate than they did in the past (Gardner et al. 2003, Bruno & Selig 2007, Bruno et al. 2009, Schutte et al. 2010, De'ath et al. 2012, Jackson et al. 2014, Hughes et al. 2018, and they have been replaced by macroalgae more often than by any other sessile organism (Norström et al. 2009, Jackson et al. 2014. Hence, understanding the dynamics of the new ecological relationships established in macroalgal-dominated states is paramount, especially those related to the top-down control exerted by herbivores. ...
Overfishing of large herbivorous fishes is connected to the rise of algal-dominated states on coral reefs. The recovery of their populations is challenging, and future herbivore assemblages may be composed of smaller fish. With fisheries now targeting these smaller-sized herbivore populations, coral reef benthic communities may face unknown outcomes. We performed caging experiments in algal-dominated reefs of Northeastern Brazil, that have been depleted of large herbivorous fishes, to appraise the effects of removing small herbivores on benthic community composition and succession. Full cages simulated herbivore removal, and partial cages and open plots functioned as controls. In total, 36 experimental plots were monitored for 1 yr, accounting for the influence of seasonal changes in local conditions of temperature and turbidity. Overall macroalgal cover did not change between experimental treatments, but filamentous algae increased 5-fold inside full cages by the end of the experiment, surpassing articulated coralline forms as the dominant group. Higher temperatures during the dry season promoted filamentous algae when the top-down control of the herbivores was removed, while a reverse pattern was observed when fishes were allowed to feed inside plots. Small herbivores accelerated benthic succession, facilitating the dominance of articulated coralline algae as the climax community. Our findings oppose previous studies performed at sites with high abundances of large-bodied fishes, where herbivory decreased overall macroalgal cover, promoted filamentous and crustose coralline algae and delayed community succession. The further depletion of smaller-bodied herbivores can trigger shifts in benthic community dynamics that interact with water temperature, which may have implications for reef resilience in an ocean-warming scenario.
... Understanding how all of the members of the coral holobiont respond in highly endangered coral species, such as Acropora cervicornis, remains a top research priority given the current rates of coral decline (Miller et al., 2002;Schutte et al., 2010;Contreras-Silva et al., 2020). Caribbean A. cervicornis populations are experiencing dramatic declines and are the focus of major restoration efforts (Schopmeyer et al., 2017;Ware et al., 2020). ...
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Global change is increasing seawater temperatures and decreasing oceanic pH, driving declines of coral reefs globally. Coral ecosystems are also impacted by local stressors, including microplastics, which are ubiquitous on reefs. While the independent effects of these global and local stressors are well-documented, their interactions remain less explored. Here, we examine the independent and combined effects of global change (ocean warming and acidification) and microplastics exposures on gene expression (GE) and microbial community composition in the endangered coral Acropora cervicornis. Nine genotypes were fragmented and maintained in one of four experimental treatments: 1) ambient conditions (ambient seawater, no microplastics; AMB); 2) microplastics treatment (ambient seawater, microplastics; MP); 3) global change conditions (warm and acidic conditions, no microplastics; OAW); and 4) multistressor treatment (warm and acidic conditions with microplastics; OAW+MP) for 22 days, after which corals were sampled for genome-wide GE profiling and ITS2 and 16S metabarcoding. Overall A. cervicornis GE responses to all treatments were subtle; however, corals in the multistressor treatment exhibited the strongest GE responses, and genes associated with innate immunity were overrepresented in this treatment. ITS2 analyses confirmed that all coral were associated with Symbiodinium ‘fitti’ and 16S analyses revealed similar microbiomes dominated by the bacterial associate Aquarickettsia, suggesting that these A. cervicornis fragments exhibited remarkably low variability in algal and bacterial community compositions. Future work should focus on functional differences across microbiomes, especially Aquarickettsia and viruses, in these responses. Overall, results suggest that when local stressors are coupled with global change, these interacting stressors present unique challenges to this endangered coral species.
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Macroalgae can modify coral reef community structure and ecosystem function through a variety of mechanisms, including mediation of biogeochemistry through photosynthesis and the associated production of dissolved organic carbon (DOC). Ocean acidification has the potential to fuel macroalgal growth and photosynthesis and alter DOC production, but responses across taxa and regions are widely varied and difficult to predict. Focusing on algal taxa from two different functional groups on Caribbean coral reefs, we exposed fleshy ( Dictyota spp.) and calcifying ( Halimeda tuna ) macroalgae to ambient and low seawater pH for 25 days in an outdoor experimental system in the Florida Keys. We quantified algal growth, calcification, photophysiology, and DOC production across pH treatments. We observed no significant differences in the growth or photophysiology of either species between treatments, except for lower chlorophyll b concentrations in Dictyota spp. in response to low pH. We were unable to quantify changes in DOC production. The tolerance of Dictyota and Halimeda to near-future seawater carbonate chemistry and stability of photophysiology, suggests that acidification alone is unlikely to change biogeochemical processes associated with algal photosynthesis in these species. Additional research is needed to fully understand how taxa from these functional groups sourced from a wide range of environmental conditions regulate photosynthesis (via carbon uptake strategies) and how this impacts their DOC production. Understanding these species-specific responses to future acidification will allow us to more accurately model and predict the indirect impacts of macroalgae on coral health and reef ecosystem processes.
The local diversity and global richness of coral reef fishes, along with the diversity manifested in their morphology, behaviour and ecology, provides fascinating and diverse opportunities for study. Reflecting the very latest research in a broad and ever-growing field, this comprehensive guide is a must-read for anyone interested in the ecology of fishes on coral reefs. Featuring contributions from leaders in the field, the 36 chapters cover the full spectrum of current research. They are presented in five parts, considering coral reef fishes in the context of ecology; patterns and processes; human intervention and impacts; conservation; and past and current debates. Beautifully illustrated in full-colour, this book is designed to summarise and help build upon current knowledge and to facilitate further research. It is an ideal resource for those new to the field as well as for experienced researchers.
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In recent decades, the cover of fleshy macroalgae has increased and coral cover has decreased on most Caribbean reefs. Coral mortality precipitated this transition, and the accumulation of macroalgal biomass has been enhanced by decreased herbivory and increased nutrient input. Populations of Acropora palmata (elkhorn coral) and A. cervicornis (staghorn coral), two of the most important framework-building species, have died throughout the Caribbean, substantially reducing coral cover and providing substratum for algal growth. Hurricanes have devastated local populations of Acropora spp. over the past 20–25 years, but white-band disease, a putative bacterial syndrome specific to the genus Acropora, has been a more significant source of mortality over large areas of the Caribbean region. Paleontological data suggest that the regional Acropora kill is without precedent in the late Holocene. In Belize, A. cervicornis was the primary ecological and geological constituent of reefs in the central shelf lagoon until the mid-1980s. After constructing reef framework for thousands of years, A. cervicornis was virtually eliminated from the area over a ten-year period. Evidence from other parts of the Caribbean supports the hypothesis of continuous Holocene accumulation and recent mass mortality of Acropora spp. Prospects are poor for the rapid recovery of A. cervicornis, because its reproductive strategy emphasizes asexual fragmentation at the expense of dispersive sexual reproduction. A. palmata also relies on fragmentation, but this species has a higher rate of sexual recruitment than A. cervicornis If the Acropora spp. do not recover, macroalgae will continue to dominate Caribbean reefs, accompanied by increased abundances of brooding corals, particularly Agaricia spp. and Porites spp. The outbreak of white-band disease has been coincident with increased human activity, and the possibility of a causal connection should be further investigated.
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The coral reefs of the Flower Garden Banks (FGB) are among the most sensitive biological communities in U.S. Federal waters of the Gulf of Mexico. In 1973, the Minerals Management Service (MMS) established a program of protective activities at those reefs. The MMS and the National Oceanic and Atmospheric Administration (NOAA) have been monitoring coral populations on a long-term basis to detect incipient changes caused by oil and gas activities. The results also help in explaining the widespread degradation of reef ecosystems observed in the Caribbean region over the past few decades. Two sites, each 100 × 100 m and 17-26 m deep, have been monitored since 1988: one on the East FGB and the other on the West FGB. The mean coverage of living hard corals exceeded 50% at the two banks in 2002-2003, consistent with estimates of coral cover in previous years. We compared our results from 2002-2003 with data collected during the same period on protected reefs within the Florida Keys National Marine Sanctuary (FKNMS). Low values of coral cover on the reefs in the FKNMS exemplify how catastrophic mortality of the formerly dominant Acropora spp. led to degradation of coral assemblages throughout the Caribbean. The FGB remained in exceptionally good condition, largely for reasons of geography; their northern location excluded the cold-sensitive acroporids, so the regional-scale loss of acroporids did not reduce coral cover. The continuing multidecadal baseline of reef condition generated by the monitoring program at the FGB will enable managers to make informed decisions in the event of future changes to their biota. © 2005 by the Marine Environmental Sciences Consortium of Alabama.
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Populations of Diadema antillarum and Tripneustes ventricosus were monitored on the forereef and backreef at Discovery Bay, Jamaica, from 1995 to 2000. On the primarily coralline substrate of the forereef, T. ventricosus densities were normally low but showed a ten-fold increase in 1998, followed by a decline to normal levels. On the backreef, with both coral and seagrass, T. ventricosus densities were normally higher but a similar peak occurred in 1999. Diadema antillarum densities remained relatively constant on the backreef but declined on the forereef in 1998, and then increased rapidly. Both urchins remained on their respective coral and seagrass habitats on the backreef, but occurred together in similar habitat on the forereef. We propose that the appearance and subsequent decline of T. ventricosus enabled D. antillarum to increase after T. ventricosus had mechanically cropped macroalgae to levels easier for D. antillarum to manage. This explanation suggests that the ephemeral appearance of T. ventricosus on coral covered with macroalgae can act as a successional stage for the reestablishment of D. antillarum.
Six coral reef locations between Miami and Key West were marked with stainless steel stakes and rephotographed periodically between 1984-1991. The monitored areas included Looe Key National Marine Sanctuary, Key Largo National Marine Sanctuary, and Biscayne National Park. All six areas lost coral species between the initial survey year and 1991. Survey areas lost between one and four species; those losses constituted 13-29% of their species richness. Five of the six areas lost live coral cover. Net losses ranged from 7.3-43.9%. In the one station showing an increase in coral cover, the increase was only for the canopy branches of Acropora palmata; understory branches of this same species lost surface area at the same rate as canopy branches gained area. For most of the common species, there was a reduction in the total number of living colonies in the community, and a diminution in the number of large, mature colonies. There was no recruitment by any of the massive frame building coral species. Sources of mortality identifiable in the photographs include: 1) black band disease and 2) "bleaching'. Loss rate of this magnitude cannot be sustained for protracted periods if the coral community is to persist in a configuration resembling historical coral reef community structure in the Florida Keys. -from Authors