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Annual benthic and fish population surveys were completed at five locations in the nearshore waters along Grenada´s southwest coast during 2008 -2010. Two survey sites are located in a newly launched Marine Protected Area (MPA). Photo Quadrat (PQ) and Point Line Intercept (PLI) surveys were used to determine substrate cover. Algae was the primary live cover increasing significantly from 45.9% in 2008 to 52.7% in 2010 (PLI). Algae was also predominant (61.0% -59.3%) in the PQ surveys although annual variation was not significant. Hard coral cover ranged from 16.5% to 15.4% (PLI) and 11.4% to12.0% (PQ) with no significant differences between years. Branching and encrusting corals occurred more frequently than massive corals. In the three annual surveys neither algal cover nor hard coral varied significantly between MPA and non-protected areas (PLI). Relative abundance of fishes along 30x2m belt transects did not vary significantly among years however density of fishes decreased significantly across years for most major groups. Chromis spp. dominated the survey sites at 65.2% in 2008 and 49.8% in 2010, followed by territorial damselfish,11.1% and 15.5%, wrasse increased from 7.3% to 15.5%. Both the substrate cover and fish survey data analyses indicated a stable but degraded community. Annual surveys are planned at these sites for the foreseeable future. Existing and future data from this project will be valuable in determining the efficacy of MPA management, guiding resource management decisions and monitoring the health status of Grenada's valuable reef systems. Rev. Biol. Trop. 60 (Suppl. 1): 71-87. Epub 2012 March 01.
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Rev. Biol. Trop. (Int. J. Trop. Biol. ISSN-0034-7744) Vol. 60 (Suppl. 1): 71-87, March 2012
Benthic and fish population monitoring associated with a marine protected
area in the nearshore waters of Grenada, Eastern Caribbean
Robert Anderson1, Clare Morrall2, Steve Nimrod2, Robert Balza1, Craig Berg3, Jonathan Jossart1
1. Wisconsin Lutheran College, 8800 W. Bluemound Rd., Milwaukee, WI 53226, USA; banderson@wlc.edu,
rob.balza@wlc.edu, jossart1@gmail.com
2. St. George’s University, P.O. BOX 7, St. George’s, Grenada, West Indies; cmorrall@sgu.edu, snimrod@sgu.edu
3. Milwaukee County Zoo, 10001 W Bluemound Road, Milwaukee, WI 53226, USA; craig.berg@milwcnty.com
Received 15-VII-2011. Corrected 1-XII-2011. Accepted 20-XII-2011.
Abstract: Annual benthic and fish population surveys were completed at five locations in the nearshore waters
along Grenada´s southwest coast during 2008 - 2010. Two survey sites are located in a newly launched Marine
Protected Area (MPA). Photo Quadrat (PQ) and Point Line Intercept (PLI) surveys were used to determine
substrate cover. Algae was the primary live cover increasing significantly from 45.9% in 2008 to 52.7% in
2010 (PLI). Algae was also predominant (61.0% - 59.3%) in the PQ surveys although annual variation was not
significant. Hard coral cover ranged from 16.5% to 15.4% (PLI) and 11.4% to12.0% (PQ) with no significant
differences between years. Branching and encrusting corals occurred more frequently than massive corals. In
the three annual surveys neither algal cover nor hard coral varied significantly between MPA and non-protected
areas (PLI). Relative abundance of fishes along 30x2m belt transects did not vary significantly among years
however density of fishes decreased significantly across years for most major groups. Chromis spp. dominated
the survey sites at 65.2% in 2008 and 49.8% in 2010, followed by territorial damselfish,11.1% and 15.5%,
wrasse increased from 7.3% to 15.5%. Both the substrate cover and fish survey data analyses indicated a stable
but degraded community. Annual surveys are planned at these sites for the foreseeable future. Existing and
future data from this project will be valuable in determining the efficacy of MPA management, guiding resource
management decisions and monitoring the health status of Grenada’s valuable reef systems. Rev. Biol. Trop. 60
(Suppl. 1): 71-87. Epub 2012 March 01.
Key words: benthic cover, coral, reef fish, monitoring, Grenada, Eastern Caribbean, marine protected area.
The island nation of Grenada is part of the
Eastern Caribbean region recently classified as
being at “very high risk” by the Reefs at Risk in
the Caribbean report (Bouchon et al. 2008). Of
the 160 km2 of reef area in Grenada 41% were
listed as having a high-risk threat index and
40% were listed as very high (Burke & Maidens
2004). The primary contributors to this rating
were coastal development and fishing pressure.
Coral communities rely on large herbivo-
rous fish species to manage levels of macroalgae
(Burkepile & Hay 2010, Ceccarelli et al. 2011,
Walsh 2011). In an analysis of the Grenadian
demersal fish catch and fishing effort from 1986
to 1993, Jeffrey (2000) found that the number of
boats employed in the demersal fishery off the
west coast of Grenada increased by 200% how-
ever the catch declined by nearly 75% during
this seven year period. Local overfishing often
targets large herbivorous species reducing these
fish stocks thus contributing to increased abun-
dance of macroalgae on coral reefs (Hawkins &
Roberts 2003). One impact of increased algal
abundance is reduced growth and recruitment
of coral polyps (Bascompte et al. 2005, Arnold
2007, Birrell et al. 2008, Mora 2008).
Introduction of excess nutrients to coral
reef systems from coastal development further
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enhances overgrowth of algae (Lapointe et
al.1997) and directly inhibits coral recruit-
ment and growth (Littler et al. 2009). These
local stressors weaken a coral community’s
resilience (Hughes 1994, Hughes et al. 2003,
Gardner et al. 2003, Wilkinson 2008) making
it more vulnerable to global climate change and
increased storm activities (Goldenberg et al.
2001, Eakin et al. 2010, Hughes et al. 2010).
Grenada has been impacted by two major hur-
ricanes in the past decade: Ivan in September
2004 and Emily in July 2005. Major storms
such as these can result in devastating effects
on reefs breaking down the basic structure
and dislodging corals leaving leveled areas of
rubble (Woodley et al. 1981).
Many countries have established Marine
Protected Areas (MPAs) that restrict some
uses of coastal reef systems with the hope
that these sections will provide a source of
biodiversity to adjacent or “down current”
locations. Unfortunately, there is a paucity
of data that demonstrates the effectiveness of
specific management practices. While the Gre-
nadian government established legislation for
the Moliniere-Beausejour MPA on the south-
west coast of the island in 2001, no significant
management practices were implemented until
2010. Permanent mooring buoys were estab-
lished in 2009, warden patrols began in 2010
and some fishing practices were restricted from
September 2010.
A development plan for Grenada’s Nation-
al Protected Areas System identified the need
for external assistance in research and monitor-
ing of Grenada’s protected areas (Mac Leod
2007). Initial surveys at nine sites off the
southwest coast of Grenada in 2006 and 2007
identified macroalgae was the most abundant
substrate cover ranging from 36.5% (± 0.8%)
to 53.2 % (± 1.2%). Hard corals covered
23.8% (± 0.9%) to 38.1% (± 1.2%) (Bouchon
et al. 2008). This 2008-2010 study builds on
the initial survey and establishes a foundation
upon which the effectiveness of the Molin-
iere-Beausejour MPA management techniques
may be evaluated.
Study Area: Five sites ranging in depth
from 5.2m-12.2m, located along Grenada’s
southwest coast were established in 2008.
Similar reefs both inside and outside the
MPA that are frequently used by the dive
industry were selected. Dragon Bay (12°
5’6.00”N 61°45’45.36”W) and Flamingo
Bay (12° 5’30.36”N 61°45’30.60”W) are in
MPAs, while Northern Exposure Shallow (12°
1’57.30”N 61°46’14.28”W), Northern Expo-
sure Deep (12° 2’22.14”N 61°46’4.74”W) and
Quarter Wreck (12° 1’40.98”N 61°47’0.84”W)
are in non-protected areas. Four 30m parallel
transects were set up at 5m intervals. Metal
stakes mark the beginning and end of each
permanent transect.
MATERIALS AND METHODS
The substrate composition of Grenada’s
southwest coast was surveyed with the Photo
Quadrat (PQ) and Point Line Intercept (PLI)
methods. The PQ method allows for care-
ful identification of substrate types from a
digital photograph. Although identification of
substrate types is not always optimal based
on digital photos this approach allowed more
intense scrutiny of the substrate since time is
not a factor in the sampling process. In addition
using Coral Point Count with Excel extensions
(CPCe) v.3.6 allowed a randomized sampling
scheme for each picture (Kohler & Gill 2006).
Since there are 60 pictures associated with
each transect this increases the total number
of observations. The PLI method developed by
Crosby & Bruckner in 2002 based on Crosby
& Reese (1996) was used to estimate relative
abundance of major types of substrate cover
and fish species associated with the coral reefs
in Grenada’s nearshore waters. Four 30m per-
manent transects were surveyed at each of the
five locations. Fish species, as well as Diadema
antillarum, abundance occurring within a two-
meter wide belt (AGRRA Protocol v. 4.0) from
the substrate to water surface along each tran-
sect were recorded. Benthic substrate was iden-
tified and recorded at a point directly below
each half-meter mark along each transect.
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Divers completed fish data collections along
each transect in ten minutes.
Sixty photo quadrats from each transect
were processed using Coral Point Count with
Excel extensions (CPCe) v.3.6 (Kohler & Gill
2006). A Canon EOS Digital Rebel XTI cam-
era in an Ikelite underwater housing was used
to take a picture at every half-meter mark.
Attached to the underwater housing was a tube
with a calibrated scale used to maintain a con-
sistent distance (60cm) from the substrate and
to assist with scaling in the CPCe software pro-
gram. The images were uploaded into the CPCe
software program, and a 20cm by 20cm square
was superimposed on the image. Eight points
were randomly generated inside the square,
and the substrate under each point was identi-
fied. Dumas et al. (2009) found that whether
nine or ninety-nine points were used in a1m2
area, the difference for large categories was not
significant. Thus for the 400 cm2 area in this
study 8 points were deemed sufficient. Also, a
Sony HDR-SR8 video camera in an Amphibico
underwater housing was used to take video of
each location to record a broader perspective of
the survey sites.
For both the PLI and PQ data a repeated
measure analysis of variance (ANOVAR) using
transects as the sampling unit was used to
monitor Grenada’s southwest benthic com-
munity and fish assemblage from 2008 to
2010. To satisfy the assumption of normal-
ity, proportional data was arcsine square root
transformed and all non-proportional data was
log transformed. The Shapiro-Wilk test, as
well as skewness and kurtosis values were used
to assess normality. Non-normal distributions
were examined, and if appropriate outliers
were removed (Zar 1999). Mauchly’s sphe-
ricity test was used to determine sphericity,
if violated the Greenhouse-Geisser correction
was used to determine significance. Addition-
ally all cases of significance were verified with
the multivariate analyses, which do not assume
sphericity. A Bonferroni correction (signifi-
cance value (0.05)/ number of comparisons
made) was used when determining significance
(Sokal and Rohlf 1995). Also, the Bonferroni
correction multiple comparison test was used
to determine among which years a significant
difference occurred.
To identify interactions between the MPA
and non-protected area from 2008 to 2010 a
two-way ANOVAR was used. This was only
done for the PLI data, because the PQ data
had an insufficient sample size. In order to
effectively make this comparison the same
sample size needed to be used for the MPA and
non-protected area. This was accomplished by
selecting two of the three non-protected loca-
tions, Quarter Wreck and Northern Exposure
Shallow. The above criteria for assessing nor-
mality, sphericity, and significance were used.
When an interaction was found to be signifi-
cant a follow up one-way analysis of variance
(ANOVA) test was used to further examine
the interaction. The same criteria for assess-
ing normality were used, and Levene’s test of
homogeneity was used to evaluate the equality
of variances. If the results of Levene’s test were
found to be significant, then a p<0.01 was used
to determine significance. The Bonferroni cor-
rection was still used when determining signifi-
cance as well (Sokal and Rohlf 1995).
RESULTS
Substrate (PLI): Algae was the dominant
substrate cover found at all locations off Grena-
da’s southwest coast (Fig. 1). Algae increased
significantly from 45.9% (SE=1.7; n=35) in
2008 to 52.7% (1.4; 35) in 2010 (ANOVAR,
F=7.431, p=0.001). Comparison of major algal
groups (macroalgae, turf and coralline) showed
that macroalgae consistently dominated the
algal community. Turf algae decreased sig-
nificantly in 2010 and coralline algae increased
significantly in 2010 (Tables 1 & 2).
Algal cover in the MPA ranged from 46.3%
(3.9; 12) to 51.4% (3.5; 12) over the three years,
while in the non-protected area it ranged from
44.0% (3.2; 12) to 50.3% (2.2; 12); no signifi-
cant interaction between time and location was
found (Two-way ANOVAR, F=1.528, p=0.239)
(Table 3). Yet the different types of algae experi-
enced significant interaction. Turf algae did have
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Fig. 1. Mean substrate cover with error bars (SE) based on Point Line Intercept surveys from Grenada’s southwest reefs
during 2008-2010; * indicates a significant difference (ANOVAR; p<0.017).
70
60
50
40
30
20
10
0
2008
2009
2010
Algae Hard Coral NL Substrate Gorgonian Sponge
Percent
TABLE 1
Mean percent cover for algal categories based on Point Line Intercept and Photo Quadrat surveys from Grenada’s
southwest reefs during 2008-2010. A Bonferroni correction of p<0.017 was used to determine significance
Category PLI Bonferroni Comparision PQ Bonferroni Comparision
nMean % SE n Mean % SE
Macroalgae 2008 32 74.7 2.1 18 70.6 1.9 2010 > 2008 (0.002)
Macroalgae 2009 32 72.4 4.7 18 67.2 1.7 2010 > 2009 (0.001)
Macroalgae 2010 32 71.7 2.2 18 78.0 2.1
Turf 2008 33 14.8 2.1 2010 < 2008 (p = 0.000) 17 3.8 0.6 2009 < 2008 (0.002)
Turf 2009 33 23.1 4.6 2010 < 2009 (p = 0.000) 17 0.8 0.3 2009 < 2010 (0.001)
Turf 2010 33 2.4 0.6 17 6.0 1.4
Coralline 2008 24 9.0 1.2 2010 > 2008 (p = 0.000) 16 24.7 2.1 2010 < 2008 (0.001)
Coralline 2009 24 4.2 0.7 2010 > 2009 (p = 0.000) 16 32.6 1.4 2010 < 2009 (0.000)
Coralline 2010 24 23.4 2.1 16 15.9 1.0
TABLE 2
ANOVAR for major Algal groups based on Point Line Intercept and Photo Quadrat surveys from Grenada’s southwest
reefs during 2008-2010. Bonferroni correction of p<0.017 was used for determining significance (* indicates significant)
Category PLI PQ
n F p n F p
Macroalgae 2008-2010 32 1.306 0.271 18 13.795 0.000*
Turf 2008-2010 33 14.577 0.000* 17 12.476 0.000*
Coralline 2008-2010 24 31.393 0.000* 16 35.969 0.000*
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a significant interaction (Two-way ANOVAR,
F=6.738, p=0.005), but the follow up tests
showed no significant differences between the
MPA and non-protected area. Coralline algae
also exhibited a significant interaction (Two-way
ANOVAR, F=17.752, p=0.000), and for 2010
the 32.4% (3.3; 12) found in the non-protected
area was significantly greater than the 18.2%
(3.6; 12) in the MPA. Macroalgae did not exhibit
any significant interaction (Two-way ANOVAR,
F=1.581, p=0.237) (Table 4).
The hard coral cover did not vary signifi-
cantly from year to year ranging from 16.5%
(1.0; 35) to 15.4% (1.3; 35) (Fig. 1) (ANOVAR,
F=0.531, p=0.591) (Fig. 1). However the type
of hard coral (massive, encrusting and branch-
ing) observed did change across the years.
Encrusting coral occurred most frequently
in 2008 however by 2010 branching coral
occurred most frequently (Tables 5 & 6).
Hard coral cover ranged from 15.2% (2.2;
12) to 19.9% (4.3; 12) in the MPA, and
14.3% (1.4; 12) to 17.6% (1.3; 12) in the
non-protected area (Table 3). Although hard
coral did not differ significantly (Two-way
ANOVAR, F=0.072, p=0.931) in overall per-
cent between the MPA and non-protected area
encrusting coral did have a significant inter-
action between time and location (Two-way
ANOVAR, F=7.049, p=0.004). Yet in follow up
analyses no significant differences between the
MPA and non-protected area was found. Mas-
sive (Two-way ANOVAR, F=3.555, p=0.046)
and branching (Two-way ANOVAR, F=3.170,
p=0.091) coral had no significant interaction
between time and location (Table 7).
While hard coral cover remained stable,
gorgonian cover significantly dropped from
3.7% (0.4; 32) and 4.0% (0.6; 32) in 2008 and
2009 to 1.8% (0.3; 32) in 2010 (ANOVAR,
F=19.609, p=0.000). Other significant changes
in the substrate were seen in the sponge and
non-living categories. Sponge cover saw a
sudden decrease from 4.6% (0.8; 35) in 2008
to 2.2% (0.4; 35) in 2009, but recovered to
4.9% (0.8; 35) in 2010 (ANOVAR, F=6.212,
p=0.005). Also non-living substrate significant-
ly decreased from 25.2% (1.7; 35) and 21.9%
(1.9; 35) in 2008 and 2009 to 14.2% (1.3; 35) in
2010 (ANOVAR, F=14.745, p=0.000) (Fig. 1).
TABLE 3
Substrate mean based on the Point Line Intercept surveys in non-protected and marine protected areas from Grenada’s
southwest reefs during 2008-2010. When the Two-way ANOVAR showed a significant interaction between time and
location, a one way ANOVA was done for further examination. A Bonferroni correction of p<0.017
was used when determining significance
Substrate Non-Protected Area Marine Protected Area ANOVA
nMean % SE n Mean % SE F p
Coral 2008 12 15.9 2.6 12 16.4 2.3
Coral 2009 12 17.6 1.3 12 15.2 2.2
Coral 2010 12 14.3 1.4 12 19.9 4.3
Gorgonian 2008 12 3.7 0.9 12 4.6 1.1 0.452 0.508
Gorgonian 2009 12 3.7 1.1 12 6.5 1.3 4.249 0.051
Gorgonian 2010 12 0.7 0.3 12 1.8 0.5 3.137 0.090
Algae 2008 12 47.6 2.6 12 46.9 3.3
Algae 2009 12 44.0 3.2 12 46.3 3.9
Algae 2010 12 50.3 2.2 12 51.4 3.5
NL Substrate 2008 12 21.6 2.5 12 23.2 3.1
NL Substrate 2009 12 23.1 2.7 12 16.1 2.5
NL Substrate 2010 12 13.6 1.9 12 15.3 3.1
Sponge 2008 12 5.6 1.9 12 5.5 0.8 0.857 0.365
Sponge 2009 12 1.4 0.7 12 4.4 1.0 7.511 .012
Sponge 2010 12 4.0 1.2 12 8.0 1.2 7.027 .015
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Further comparisons of percent cover in
the MPA to non-protected areas revealed that
gorgonian cover did have a significant interac-
tion (Two-way ANOVAR, F=13.005, p=0.000).
Additional tests of gorgonian cover in the MPA
and non-protected areas showed no significant
difference among years. Sponge cover also
exhibited a significant interaction (Two-way
ANOVAR, F=8.654, p=0.002). The sponge
cover in the MPA was not significantly different
TABLE 4
Algae type mean based on the Point Line Intercept surveys in non-protected and marine protected areas from Grenada’s
southwest reefs during 2008-2010. When the Two-way ANOVAR showed a significant interaction between time and
location, a one way ANOVA was done for further examination. A Bonferroni correction of p<0.017
was used when determining significance
Algae Type Non-Protected Area Marine Protected Area ANOVA
nMean % SE n Mean % SE F P
Macroalgae 2008 12 70.3 2.9 12 75.6 2.9
Macroalgae 2009 12 64.0 8.1 12 87.3 2.5
Macroalgae 2010 12 63.7 3.2 12 78.5 4.1
Turf 2008 12 17.7 4.1 12 16.1 2.0 0.005 0.945
Turf 2009 12 29.9 7.9 12 8.4 2.0 4.595 0.043
Turf 2010 12 2.1 0.9 12 3.1 1.2 0.237 0.631
Coralline 2008 12 10.6 2.8 12 8.5 1.8 0.143 0.709
Coralline 2009 12 4.9 2.0 12 4.4 1.1 0.161 0.692
Coralline 2010 12 32.4 3.3 12 18.2 3.6 7.329 0.013
TABLE 5
Mean percent cover for hard coral categories based on Point Line Intercept and Photo Quadrat surveys from Grenada’s
southwest reefs during 2008-2010. A Bonferroni correction of p<0.017 was used to determine significance
Category Photo Quadrat Bonferroni
Comparison
Point Line Intercept Bonferroni
Comparison
n Mean SE n Mean SE
Massive 2008 18 36.8 3.6 35 12.9 2.1 2008<2009 (p=0.003)
Massive 2009 18 31.3 3.4 35 27.6 3.1 2008<2010 ( p=0.007)
Massive 2010 18 30.5 3.1 35 26.4 3.4
Branching 2008 19 41.0 6.0 35 32.3 3.9
Branching 2009 19 43.5 4.1 35 45.8 3.5 2008<2010 ( p=0.017)
Branching 2010 19 42.8 4.1 35 44.7 3.9
Encrusting 2008 19 22.2 4.0 31 47.9 4.5 2008 > 2009 ( p=0.000)
Encrusting 2009 19 22.0 2.8 31 21.9 2.9 2008 > 2010 ( p=0.000)
Encrusting 2010 19 25.2 2.8 31 21.1 2.9
TABLE 6
ANOVAR for major coral forms based on Point Line Intercept and Photo Quadrat surveys from Grenada’s southwest reefs
during 2008-2010. Bonferroni correction of p<0.017 was used for determining significance
Coral Form Point Line Intercept Photo Quadrat
n F p n F p
Massive 2008-2010 35 8.626 0.000* 18 1.630 0.211
Branching 2008-2010 35 4.714 0.012* 19 0.100 0.799
Encrusting 2008-2010 31 13.409 0.000* 19 0.798 0.458
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from the non-protected area in 2008; however
sponge cover in 2009 and 2010 showed that the
MPA sponge cover was significantly greater
than the non-protected area (Table 3).
Substrate (Photo Quadrat): Algae, the
dominant substrate cover, ranging from 61.0%
(1.5; 19) in 2008, 59.9% (1.9; 19) in 2009
and 59.3% (1.8, 19) in 2010 showed no sig-
nificant annual differences (ANOVAR, F=0.373,
p=0.616) (Fig. 2). Although the percent cover
of algae did not change across years, the type
of algae observed did. Macroalgae which
occurred more frequently than other types of
algae increased significantly in 2010. Turf algae
dipped significantly in 2009 and coralline algae
decreased significantly in 2010 (Table 1 & 2).
Percent hard coral cover remained sta-
ble across years ranging from 11.4% (0.7;
18) to 12.0% (1.1; 18) (ANOVAR, F=0.037,
p=0.964). Of the three hard coral forms record-
ed branching coral occurred most frequently
with no significant annual variation (Table 3 &
4). Cyanobacteria which was not recorded over
the three year sampling period with the PLI
method was similar in percent cover to hard
coral ranging from 14.7% (1.5; 19) to 11.9%
(1.7; 19) (ANOVAR, F=1.314, p=0.277). Per-
cent sponge cover did increase significantly
from 1.6% (0.4; 19) in 2008 to 4.2% (0.7; 19)
in 2010 (ANOVAR, F=9.478, p=0.002, Bonfer-
roni p=0.004) (Fig. 2).
Fish: A total of 62 fish species were
observed at the five sampling locations from
2008 to 2010 (Table 8). The major groups of
fish analyzed included Chromis spp., damsel-
fishes, parrotfishes, surgeonfishes, and wrasse.
Chromis spp. were separated from the damsel-
fishes because of their large number. Diversity
indices were quite high and similar across all
sites (Table 9).
Relative abundance of all but one of the
most frequently occurring groups of fishes
did not vary significantly across the three
years of this study. Chromis spp., the largest
group observed, showed a downward trend
going from 65.2% (3.5; 34) to 49.8% (4.2;
34); however the difference was not significant
(ANOVAR, F=3.611, p=0.032). Damselfishes
ranged from 11.1% (1.7; 32) to 15.5% (1.7;
32) (ANOVAR, F=3.531, p=0.035) and par-
rotfishes from 10.1% (1.6; 36) to 6.4% (0.7;
36) (ANOVAR, F=1.732, p=0.184) (Fig. 3).
Surgeonfishes also remained stable between
0.9% (0.1; 31) and 1.3% (0.2; 31) (ANOVAR,
F=0.146, p=0.864). Wrasse however showed
a significant increase from 7.3% (1.0; 35)
to 15.5% (2.1; 35) (ANOVAR, F=7.341,
p=0.001) (Fig. 3).
TABLE 7
Coral Form mean based on the Point Line Intercept surveys in non-protected and marine protected areas from Grenada’s
southwest reefs during 2008-2010. When the Two-way ANOVAR showed a significant interaction between time and
location, a one way ANOVA was done for further examination. A Bonferroni correction of p<0.017
was used when determining significance
Coral Form Non-Protected Area Marine Protected Area ANOVA
nMean % SE n Mean % SE F P
Massive 2008 12 7.8 2.6 12 19.9 5.0
Massive 2009 12 23.4 4.9 12 34.1 6.2
Massive 2010 12 24.6 5.2 12 30.7 6.6
Branching 2008 12 39.9 9.4 11 29.1 7.0
Branching 2009 12 58.5 4.7 11 40.6 4.9
Branching 2010 12 54.1 7.1 11 34.2 9.0
Encrusting 2008 12 46.9 8.7 12 42.6 8.2 0.195 0.663
Encrusting 2009 12 13.5 3.4 12 17.7 3.3 0.568 0.459
Encrusting 2010 12 18.1 4.0 12 17.7 6.7 0.137 0.714
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TABLE 8
Fish species observed during surveys at five sampling locations over Grenada’s southwest reefs during 2008-2010
Acanthuridae Haemulidae Pomacentridae
Acanthurus coeruleus Haemulon chrysargyreum Holacanthus tricolor
Acanthurus chirurgus Haemulon flavolineatum Chromis cyanea
Acanthurus bahianus Haemulon spp. Chromis multilineata
Acanthurus spp. Holocentridae Stegastes partitus
Apogonidae Myripristis jacobus Abudefduf saxatilis
Apogon townsendi Holocentrus rufus Stegastes leucostictus
Apogon spp. Holocenthus coruscus Stegastes diencaeus
Aulostomidae Holocentrus adscensionis Stegastes planifrons
Aulostomus maculatus Grammatidae Microspathodon chrysurus
Balistidae Gramma loreto Scaridae
Monacanthus spp. Labridae Scarus vetula
Blenniidae Thalassoma bifasciatum Sparisoma aurofrenatum
Blennidea spp. Clepticus parrae Sparisoma viride
Bothidae Halichoeres bivittatus Scarus spp.
Bothus lunatus Bodianus rufus Sciaenidae
Carangidae Halichoeres garnoti Equetus lanceolatus
Carangoides ruber Xyrichtys spp. Equetus punctatus
Decapterus macarellus Lutjanidae Scorpaenidae
Cirrhitidae Lutjanus synagris Scorpaena plumieri
Amblycirrhitus pinos Lutjanus mahogoni Serranidae
Chaetodontidae Ocyurus chrysurus Cephalopholis fulva
Chaetodon capistratus Lutjanus spp. Cephalopholis cruentata
Chaetodon striatus Mullidae Serranus tigrinus
Chaetodon spp. Pseudupeneus maculatus Hypoplectrus spp.
Diodontidae/Tetraodontidae Mulloidichthys martinicus Hypoplectrus guttavarius
Canthigaster rostrata Ophichthidae Hypoplectrus chlorurus
Gobiidae Myrichthys breviceps Synodontidae
Coryphopterus glaucofraenum Ostraciidae Synodus intermedius
Coryphopterus hyalinus Acanthostracion quadricornis
Elacatinus genie Acanthostracion polygonius
Muraenidae Priacanthidae
Echidna catenata Priacanthus arenatus
TABLE 9
Shannon-Wiener diversity index based on identified species observed during surveys over Grenada’s southwest reefs
during 2008-2010. (Chromis were excluded because their large numbers would dominate the index)
Location 2008-10 2008 2009 2010
H’ Richness H’ Richness H’ Richness
Dragon Bay 2.346 37 2.032 29 2.218 36
Flamingo Bay 2.183 27 2.459 30 2.217 30
N.E Shallow 2.417 29 2.143 32 2.061 25
N.E. Deep 2.392 35 2.608 33 2.411 30
Quarter Wreck 2.527 38 2.309 31 2.333 32
All Locations 2.548 51 2.598 49 2.500 53
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In comparing the MPA to the non-protect-
ed area, a significant interaction between time
and location was observed for the chromis,
which ranged from 47.8% (6.8; 12) to 77.1%
(3.7; 12) in the MPA and 42.0% (6.4; 12) to
45.8% (6.7; 12) in the non-protected area (Two-
way ANOVAR, F=6.303, p=0.007). Additional
tests revealed that percent chromis observed
in 2008 was significantly lower in the non-
protected area then the MPA (Table 10). The
wrasse group also had a significant interac-
tion between time and location (Table 11).
During 2008 the wrasse were significantly
higher in the non-protected area at 11.9% (1.9;
12), whereas the MPA only had 3.5% (1.1;
12) wrasse (Table 10). None of the other fish
groups showed a significant interaction at time
and location (Table 11).
The density of fishes on the other hand did
show significant differences for most groups
Fig. 2. Mean substrate cover with error bars (SE) based on Photo Quadrat surveys from Grenada’s southwest reefs during
2008-2010; * indicates a significant difference (ANOVAR; p<0.017).
70
60
50
40
30
20
10
0
2008
2009
2010
Algae Hard Coral NL Substrate Gorgonian Sponge Cyanobacteria
Percent
Fig. 3. Mean fish composition with error bars (SE) based on Point Line Intercept surveys from Grenada’s southwest reefs
during 2008-2010;* indicates a significant difference (ANOVAR; p<0.017).
70
60
50
40
30
20
10
0
2008
2009
2010
Chromis Damsel Parrot Wrasse Surgeon
Percent
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Rev. Biol. Trop. (Int. J. Trop. Biol. ISSN-0034-7744) Vol. 60 (Suppl. 1): 71-87, March 2012
over the years of the study. Chromis spp.
decreased significantly from 669.3 fish/100m2
(180.5; 30) to 286.6 fish/100m2 (78.3; 30)
(ANOVAR, F=9.215, p=0.000). Damselfish-
es density also significantly decreased from
70.3 fish/100m2 (3.7; 34) in 2008 to 40.6
fish/100m2 (2.7; 34) in 2009 (Bonferroni,
p=0.000) and 55.3 fish/100m2 (5.2; 34) in 2010
(Bonferroni, p=0.015) (ANOVAR, F=17.994,
p=0.000). The density of parrotfishes signifi-
cantly decreased from 39.5 fish/100m2 (3.2;
30) and 39.7 fish/100m2 (4.2; 30) in 2008
and 2009 to 26.3 fish/100m2 (4.5; 30) in 2010
(ANOVAR, F=10.786, p=0.000). Wrasse den-
sity however showed an increase from 37.6
fish/100m2 (4.6; 34) and 30.2 fish/100m2 (3.5;
34) in 2008 and 2009 to 68.6 fish/100m2 (15.4)
in 2010 but the change was not significant
(ANOVAR, F=3.525, p=0.035). The density
of surgeonfishes did not significantly change,
however it showed a downward trend going
from 6.3 fish/100m2 (0.8; 25) in 2008 to 5.9
fish/100m2 (1.4; 25) in 2009, and finally to
4.5 fish/100m2 (0.5; 25) in 2010 (ANOVAR,
F=1.859, p=0.179) (Fig. 4). The only fish
group that experienced a significant interac-
tion between time and location for density
was damselfish (Two-way ANOVAR, F=7.288,
p=0.016) (Table 11). Damselfish in 2010 were
significantly higher in the non-protected area
at 54.9% (3.5; 11), while only 36.8% (4.8; 12)
were observed in the MPA (ANOVA, F=9.600,
p=0.005) (Table 12).
The observed fish assemblage was divided
into feeding groups based on the classifica-
tion of Sadin (2008b). Combined data from
all sites across years (2008-2010) showed the
dominant feeding group of the assemblage
to be planktivores at 81.3% (1.8%; 35) to
74.7 (3.5%; 31). Herbivores represented 9.7%
(1.0%; 35) to 13.6 (2.0%; 36), while carnivores
comprised 10.9 (1.3%; 30) to 14.9% (2.2; 34).
Fish feeding groups were not significantly dif-
ferent between years. In addition there was no
significant difference between the MPA and
non-protected areas in the percent plankti-
vores (Two-way ANOVAR, F=3.891, p=0.036),
herbivores (Two-way ANOVAR, F=2.900,
p=0.078) or carnivores (Two-way ANOVAR,
TABLE 10
Mean Fish percent based on the Point Line Intercept surveys in non-protected and marine protected areas from Grenada’s
southwest reefs during 2008-2010. When the Two-way ANOVAR showed a significant interaction between time and
location, a one way ANOVA was done for further examination. A Bonferroni correction of p<0.017
was used when determining significance
Fish Observed Non-Protected Area Marine Protected Area ANOVA
nMean % SE n Mean % SE F p
Chromis 2008 12 42.7 6.4 12 77.1 3.7 20.476 0.000
Chromis 2009 12 42.0 7.6 12 63.2 8.2 3.529 0.074
Chromis 20010 12 45.8 6.7 12 47.8 6.8 0.025 0.876
Damselfish 2008 12 21.1 2.9 12 9.7 1.4
Damselfish 2009 12 15.3 3.3 12 9.3 2.7
Damselfish 2010 12 18.0 3.0 12 14.6 2.8
Parrotfish 2008 12 9.6 1.7 12 3.9 0.6
Parrotfish 2009 12 13.2 2.8 12 6.4 1.8
Parrotfish 2010 12 7.0 1.1 12 5.3 1.5
Surgeonfish 2008 11 1.7 0.4 12 0.6 0.1
Surgeonfish 2009 11 1.2 0.4 12 1.0 0.4
Surgeonfish 2010 11 0.8 0.3 12 1.7 0.5
Wrasse 2008 12 11.9 1.9 12 3.5 1.1 18.988 0.000
Wrasse 2009 12 8.0 2.0 12 10.3 2.4 0.522 0.478
Wrasse 2010 12 14.8 2.2 12 23.5 4.5 2.576 0.123
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F=2.490, p=0.111) since none exhibited a sig-
nificant interaction between time and location.
Combined Diadema antillarum density for
Grenada’s southwest coast exhibited a signifi-
cant downward trend having 3.1 urchins/100m2
(0.5; 36) in 2008, to 1.9 urchins/100m2 (0.5;
36) in 2009 and to only 0.2 urchins/100m2 (0.1;
36) in 2010 (ANOVAR, F=6.078, p=0.004). It
should be noted even after log transformation
the data did not fulfill the assumption of nor-
mality, however sphericity could be assumed.
There was also no significant interaction at time
and location for diadema (Two-Way ANOVAR,
F=1.853, p=0.197).
DISCUSSION
Data collected during three annual sur-
veys indicates benthic cover in the nearshore
waters off the southwest coast of Grenada was
similar to many reported findings from across
the Caribbean. Algae dominated the substrate
(45.9% to 61.0%) and live hard coral cover-
age (16.5% to 11.4%) was quite low. Algae
TABLE 11
Two-way ANOVAR of Fish percent and density at time and location from non-protected and marine protected areas from
Grenada’s southwest reefs during 2008-2010. A bonferroni correction factor of p<0.017
was used to determine significance (*indicates significant)
Interaction Fish Percent Fish Density
nFpnFp
Chromis Time*Location 12 6.303 0.007* 10 1.965 0.169
Damsel Time*Location 12 4.424 0.024 11 7.288 0.016*
Parrotfish Time*Location 12 1.784 0.191 12 0.072 0.931
Surgeonfish Time*Location 10 2.279 0.131 10 0.192 0.183
Wrasse Time*Location 12 13.656 0.000* 11 3.595 0.046
TABLE 12
Mean Fish density based on the Point Line Intercept method from non-protected and marine protected areas from
Grenada’s southwest reefs during 2008-2010. If the Two-way ANOVAR showed a significant interaction between time
and location, a follow up one way ANOVA was done for further examination. A Bonferroni correction of p<0.017
was used when determining significance
Fish Group Non-Protected Area Marine Protected Area ANOVA
nMean (fish/100m2) SE n Mean (fish/100m2) SE F p
Chromis 2008 11 439.6 88.6 11 498.6 112.2
Chromis 2009 11 422.0 192.7 11 972.3 378.6
Chromis 20010 11 348.3 171.6 11 171.1 26.7
Damselfish 2008 11 69.4 6.5 12 64.9 4.7 0.294 0.593
Damselfish 2009 11 43.4 4.4 12 27.9 4.7 7.559 0.012
Damselfish 2010 11 54.9 3.5 12 36.8 4.8 9.600 0.005
Parrotfish 2008 12 49.0 6.0 12 22.0 3.5
Parrotfish 2009 12 41.3 5.4 12 18.9 3.9
Parrotfish 2010 12 30.5 9.0 12 13.1 2.8
Surgeonfish 2008 12 4.1 0.6 11 7.3 1.5
Surgeonfish 2009 12 5.0 1.1 11 6.0 2.9
Surgeonfish 2010 12 3.1 0.8 11 3.8 0.8
Wrasse 2008 12 42.8 7.6 12 46.1 9.5
Wrasse 2009 12 24.0 3.3 12 39.4 6.2
Wrasse 2010 12 88.7 37.8 12 75.1 21.1
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dominated systems have been reported for
many nearshore communities in the Carib-
bean (Hughes 1994, Gardner 2003, Burke &
Maidens 2004, Bouchon et al. 2008, Wilkin-
son 2008, Mumby 2009, Walsh 2011). Algae
has been the dominant substrate cover on
Caribbean reefs since a major ecological
phase shift occurred in the 1980s. Overfish-
ing, hurricane damage and a disease-induced
die-off of D. antillarum have been proposed
as major factors in this shift (Hughes 1994,
Gardner et al. 2003).
Low densities of D. antillarum in Grena-
dian nearshore waters may be one of the key
factors in the high algal component of this
benthic community. The mean D. antillarum
density found in 2x30m belt transects off the
coast of Grenada during this study ranged from
0.002/m2 to 0.031/m2 which is much lower than
the 4.25/m2 densities measured in 2003 by Car-
penter & Edmunds (2006) for these waters and
the 1.7-8.9/m2 they found associated with reefs
of six countries around the Caribbean. Based
on general surveys across a spectrum of west-
ern Atlantic reefs between 1998-2000 Kramer
(2003) reported mean D. antillarum densities
of 0.029/m2. Newman et al. (2006) found mean
densities of 0.019/m2 at similar depths in the
western and northern Caribbean. In both stud-
ies fleshy macroalgae generally dominated the
reef benthic communities where these low D.
antillarum densities occurred.
Given the importance of D. antillarum in
the coral reef community reestablishment of D.
antillarum may have potential as a management
tool to enhance coral growth in algal dominated
systems. This potential became apparent when
a phase shift reversal was noted on Jamaica’s
north coast. Coral cover increased from 23%
in 1995 to 54% in 2004 with higher growth
rates of juvenile corals and higher densities of
small juvenile recruits in “dense urchin zones”
(Idjadi et al. 2006, 2010, Bechtel et al. 2006).
The potential impact of increased numbers
of D. antillarum on coral recovery sparked
introductions of additional D. antillarum into
Grenada’s MPA from adjacent populations in
2011 (Nimrod personal communication). These
relocations will hopefully result in significant
increases in local populations of D. antillarum
that will reduce macroalgae and facilitate an
increase in coral recruitment and growth.
Understanding the composition of Gre-
nada’s southwest coastal nearshore fish com-
munity will also inform existing and future
fisheries management practices. Heavy fishing
900
800
700
600
500
400
300
200
100
0
2008
2009
2010
Chromis Damsel Parrot Wrasse Surgeon
Fish/100 m2
Fig. 4. Mean fish density with error bars (SE) based on Point Line Intercept surveys from Grenada’s southwest reefs during
2008-2010; * indicates a significant difference (ANOVAR; p<0.017).
83
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pressure has been identified as one of the key
factors in transformation of coral reefs to algal
dominated systems (Hawkins & Roberts 2003).
Fishing methods in Grenada include beach
seining, trap nets, hand lines and spearing. Tar-
get species are mainly carnivores such as Lut-
janidae (snapper), Serranidae (groupers) and
Carangidae (jacks, pompanos and mackerels
and scad) (Finlay 2000). Large herbivores such
as Scaridae (parrotfish) and Acanthuridae (sur-
geonfishes and tang) are also frequently seen
in Grenadian fish markets. Observations during
2008-2010 indicated that planktivores (74.7
- 81.3%) dominated the nearshore Grenadian
fish community followed by herbivores (9.7
- 13.6%), carnivores (10.9 - 13.9%). The her-
bivore component of Grenada’s nearshore fish
assemblage seems low when compared to other
studies. Toller et al. (2010) found 65% herbi-
vores off Saba Island in habitat types similar to
those in Grenada. In a synthesis of Caribbean
wide surveys between 1998 and 2000, Kramer
(2003) found herbivores made up 64.6% of the
fish community sampled. Simply determining
that the herbivore component of the Grenadian
fish community is low compared to other loca-
tions does not allow a full understanding of the
impact this has on substrate cover. Burkepile
& Hay (2010) pointed out the importance of
species level identification in reef fish monitor-
ing. Each herbivorous species can have unique
impacts on algal succession and coral growth.
A diverse assemblage of herbivorous fishes can
reduce development of macroalgae communi-
ties and thereby enhance recruitment of coral to
open substrates. Ceccarelli et al. (2011) divides
herbivorous fishes into roving herbivores or
“foragers” (parrotfish Scarus spp. and surgeon-
fish Acanthurus spp.) and “farmers” (territorial
damselfish Stegastes spp.) in order to evaluate
their potential influence on algal succession
and coral reef recovery. “Farmers” tend to sup-
press algal succession preventing development
of the fleshy macroalgae stage. “Foragers” have
an intermediate effect allowing development of
some macroalgae but not a late-successional
assemblage (Ceccarelli et al. 2011). In Grena-
da’s nearshore fish community herbivores were
dominated by parrotfishes (Scaridae) at 70.2%
followed by territorial damselfish fish (Poma-
centrus spp., Stegastes spp., Microspathodon
spp.) at 17.9% and surgeonfish (Acanthurus
spp.) at 11.5%. Thus “farmers” comprised only
17.9% in the Grenadian nearshore herbivorous
fish community while “foragers” made up
82.1%. It is understandable therefore that turf
algae comprised such a small portion of the
algal community and fleshy macroalgae made
up the majority. Arnold (2007) demonstrated
that grazing by scrapers such as parrotfish and
urchins facilitate coral recruitment more than
territorial damselfishes that maintain low levels
of turf algae. Since the species composition
of herbivores in Grenada’s nearshore waters
is primarily comprised of “foragers” rather
than “farmers” potential benefits are likely for
future coral recruitment if the overall number
of herbivores can be increased. It is hoped
that newly implemented fishing restrictions in
the Moliniere-Beausejour MPA will facilitate
increased abundance of herbivorous fishes.
In addition to low numbers of herbivores,
algal dominance is also driven by increases
in nutrients in nearshore waters. Littler et al.
(2009) described the importance of taking
into consideration the complex interaction of
herbivory, nutrient levels and stochastic events
in understanding existing conditions and devel-
oping management strategies for coral reef
communities. Lapointe et al. (1997) argued that
nutrient input from non-point source pollution
related to development and population increas-
es on the island of Jamaica was a major factor
in driving the shift from a coral dominated
system to an algal dominated community. In a
comparative study of reef communities Sandin
et al. (2008a) saw a shift from dominance by
a few large top predator fish species to domi-
nance by small lower trophic level consumers,
primarily planktivores, in areas of increasing
human populations. The dominance of plank-
tivores (primarily Chromis spp.) in Grena-
dian nearshore waters may be an indicator of
excess nutrients into these waters. Two major
rivers (St. Johns and Beausejour), flow into
the nearshore waters of Grenada’s southwest
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coast. These rivers drain heavily populated
areas as well as agricultural lands and have
the potential of delivering excess nutrients into
the reef communities. These nutrients have the
potential of enhancing macroalgal growth and
inhibiting the recruitment and growth of coral
(Littler et al. 2009).
The three years of monitoring at perma-
nent transects in this study provide a basis
for future trend analysis and evaluation of
management practices. Hughes et al. (2010)
advocates long term monitoring of important
taxonomic groups as well as identification of
mechanisms and feedbacks in order to detect
indicators of phase shifts. He also encourages
agencies involved in research and management
of reefs to take a proactive integrative approach
through education of grassroots constituencies,
enhancing access to existing information and
expertise and strengthening regulations associ-
ated with harvesting important species from
these communities. This approach is beginning
to be implemented in Grenada through the
work of the Grenada Government Fisheries
Division and the Moliniere-Beausejour Marine
Protected Area Stakeholder Group.
This study establishes a baseline of infor-
mation but long term and more specific monitor-
ing is needed to better understand the trajectory
of Grenada’s reef communities. Gardner et al.
(2003) indicated that areas of coral recovery
are often dominated by non-framework build-
ers such as Agaricia and Porites rather than
framework builders such as Acropora and
Montastrea. These framework builders that
formerly dominated reefs in the Caribbean are
essential to surviving the destructive forces of
major storms. The coral community in Gre-
nada’s nearshore waters is comprised primarily
of branching coral much of which is Agaricia
and Porites. Given the importance of frame-
work builders to the resilience of coral reef
communities identification of coral species will
be added to the monitoring program to better
understand the coral community.
The similarity between the MPA and non-
protected areas seen in this study may be due
to the fact that the Moliniere-Beausejour MPA
management plan was not fully implemented
until September 2010. After full implementa-
tion of the plan wardens began to patrol the
area and prevent fishing from boats and enforce
the use of permanent mooring buoys by divers
and snorkelers in the MPA. Future monitoring
efforts will be able to use the results of this
study as a basis for comparison in order to
assess the impact of the newly implemented
management practices in the MPA. Expan-
sion of current studies will allow a better
understanding of mechanisms and feedbacks
in these reef systems. Video and photographs
of transects and surrounding habitats are being
incorporated into public presentations for Gre-
nadian resource managers and the general pub-
lic to encourage a broader understanding of the
importance of careful resource management.
In addition to focusing on local environ-
ments it is important to connect these studies
to broader ecosystem wide analyses. Ogden
(2010) encourages moving toward an ecosys-
tem-based management plan for the Caribbean.
Ogden cites plans for regional management
inspired by the CARICOMP network of marine
laboratories and encourages going beyond local
problems and addressing issues like the D.
antillarum die-off, wide spread white band
disease and the annual plume of discharge from
Venezuela’s Orinoco River. Efforts are ongo-
ing to strengthen connections of this ongoing
monitoring effort to the network of Caribbean
marine laboratories and provide information
that will assist regional management.
ACKNOWLEDGEMENTS
Funding for this project was provided by
the Fischer Family Foundation and Mr. Gary
Stimac and is greatly appreciated. A special
thanks to Jacob Krause for playing a major
role in developing this program. Thanks are
also offered to Jillian Groeschel, Kyle Fos-
ter, Svetlana Bornschlegl, Victoria Krueger,
Thomas Dietrich, Ben Hermanson, Laurelyn
Dexter, Angela Majeskie, Emily Bolda, Allison
Page, and Angela Blasezyk for data collection.
Kayli Giertych and Stephen Vandenberg are
85
Rev. Biol. Trop. (Int. J. Trop. Biol. ISSN-0034-7744) Vol. 60 (Suppl. 1): 71-87, March 2012
thanked for assistance with the manuscript. Bil-
lie Harrison of the Racine Zoo is also thanked
for field assistance.
RESUMEN
Un estudio sobre poblaciones bentónicas y de peces
fue realizado en cinco localidades en la zona costera en
el suroeste de Grenada entre 2008 y 2010. Dos sitios se
ubicaron en una Área Marina Portegida (AMP) reciente-
mente creada. Para determinar la cobertura se utilizaron
foto-cuadrantes (FQ) y transectos de intersección de puntos
(TIP). Las algas fueron el principal componente del bentos,
aumentando significativamente de 45,9% en 2008 a 52,7%
en 2010 (TIP). Las algas también fueron predominantes
(61,9%-59,3) en los FQ, aunque las diferencias anuales no
fueron significativas. La cobertura de corales pétreos tenía
un ámbito de 16,5% a 15,4% (TIP) y de 11,4% a 12,0%
(FQ), sin diferencias significativas entre años. Los corales
ramificados e incrustantes fueron más frecuentes que los
corales masivos. En los tres años no hubo diferencias
significativas entre las AMPs y las áreas no protegidas.
La abundancia relativa de peces a lo largo de un transecto
de 30x2m no varió significativamente entre los años, sin
embargo, la densidad de peces decreció significativamente
a través de los años, para los grupos principales. Chromis
spp. predominó con 65,2% en 2008 y 49,8% en 2012,
seguido por damiselas territoriales, 11,1% y 15,5%, y los
lábridos aumentaron de 7,3% a 15,5%. Tanto la coberura
del sustrato como los datos de peces indican una comuni-
dad estable pero degradada. Sondeos anuales están planea-
dos para el futuro. Los datos existentes y futuros de este
proyecto serán muy útiles para determinar la eficacia de la
gestión de las AMPs y el estado de salud de los sistemas
arrecifales de Grenada.
Palabras clave: cobertura bentónica, coral, peces de arre-
cife, monitoreo, Grenada, Caribe Oriental.
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... Spalding et al. (2001) indicated that even though there are fringing and patch reefs across all coasts of Grenada also highlighted that " the total area of reef is not great " , presumably referring to contiguous reef habitat or live coral cover. The majority of Grenada's shallow reef environment is overgrowing with algae (Anderson et al. 2012). Deeper more offshore reefs have been noted as being relatively healthier, with algal growth said to be mostly seasonal (Creary 2008). ...
... Deeper more offshore reefs have been noted as being relatively healthier, with algal growth said to be mostly seasonal (Creary 2008). Anderson et al. (2012) further report that existing coral reef habitat in Grenada's nearshore waters is comprised mostly of low-density stands of branching corals: Agaricia spp. and Porites spp. ...
... Of these, 81 fish have been assessed under the protocol of the IUCN Red List of Threatened Species, and 23 species are currently red-listed (Table 9; IUCN 2013). Past annual surveys conducted at five reefs across the southwest coast (i.e., Grand Anse) showed that fish diversity indices were high and similar across sites, but that the density of most major fish groups examined decreased significantly from 2008 to 2010 (Anderson et al. 2012). Overfishing of reef fish in Grenada has been documented in the past (Jeffrey 2000) and remains a major threat largely unabated (see Table 4). ...
... Spalding et al. (2001) indicated that even though there are fringing and patch reefs across all coasts of Grenada also highlighted that " the total area of reef is not great " , presumably referring to contiguous reef habitat or live coral cover. The majority of Grenada's shallow reef environment is overgrowing with algae (Anderson et al. 2012). Deeper more offshore reefs have been noted as being relatively healthier, with algal growth said to be mostly seasonal (Creary 2008). ...
... Deeper more offshore reefs have been noted as being relatively healthier, with algal growth said to be mostly seasonal (Creary 2008). Anderson et al. (2012) further report that existing coral reef habitat in Grenada's nearshore waters is comprised mostly of low-density stands of branching corals: Agaricia spp. and Porites spp. ...
... Of these, 81 fish have been assessed under the protocol of the IUCN Red List of Threatened Species, and 23 species are currently red-listed (Table 9; IUCN 2013). Past annual surveys conducted at five reefs across the southwest coast (i.e., Grand Anse) showed that fish diversity indices were high and similar across sites, but that the density of most major fish groups examined decreased significantly from 2008 to 2010 (Anderson et al. 2012). Overfishing of reef fish in Grenada has been documented in the past (Jeffrey 2000) and remains a major threat largely unabated (see Table 4). ...
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By 1999, populations of the sea urchin Diadema antillarum had begun a dramatic resurgence on the north coast of Jamaica after 23 years of stasis at very low levels. This increase in D. antillarum, from population levels near zero in 1984 to densities as high as 16 m 2 in 2000, is associated with increases in abundance of the sympatric echinoids Echinometra viridis and Eucidaris tribuloides. In contrast, Tripneustes ventricosus was abundant on the fore reef in 1999 (unusual in that T. ventricosus generally inhabits back reef environments) but declined dramatically by 2000. Geographical Information Systems (GIS) analysis showed that D. antillarum rarely occurred alone: in 1999 and 2000, D. antillarum co-occurred with a second urchin species in 89.95% and 65.47% of the area surveyed respectively. Findings suggest that interactions between members of the echinoid complex are potentially important for reef recovery. Recent research conducted on the recovery of the D. antillarum population suggest that the presence of T. ventricosus on the fore reef may have created a disturbance large enough to facilitate a phase transition from algal to coral dominated substratum (Woodley et al. 1999). Our results are consistent with the findings of Woodley et al. (1999). We propose that recruitment of D. antillarum is facilitated by the presence of sympatric echinoids and is not dependent upon food availability. Sizes of D. antillarum populations at five sites were normally distributed, indicating strong, continued recruitment and suggesting that conditions conducive to reef recovery on the north coast of Jamaica have begun.
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Threshold levels (i.e., tipping points where the probability of community phase shifts is increased and the potential for recoverability is reduced) for critical bottom-up interactions of productivity (e.g., nutrients) and those for top-down disturbances (e.g., herbivory) must be known to manage the competitive interactions determining the health of coral-dominated reefs. We further posit that latent trajectories (reduced resiliencies/ recoverability from phase shifts) are often activated or accelerated by large-scale sto-chastic disturbances such as tropical storms, cold fronts, warming events, diseases, and predator outbreaks. In highly diverse and productive reef ecosystems, much of the overall diversity at the benthic primary producer level is afforded by the interaction of opposing nutrient-limiting/nutrient-enhancing and herbivory controls with the local physical and spatial variability, such that a mosaic of environmental conditions typically occur in close proximity. Although the relative dominance model (RDM) appears straightforwardly simple, because of the nature of direct/indirect and stimulating/limiting factors and their interactions it is extremely complex. For example, insuffi cient nutrients may act directly to limit fl eshy algal domination (via physiological stress); conversely, abundant nutrients enhance fl eshy algal growth, with the opposite effect on reef-building corals (via toxic inhibition or increased diseases). Furthermore, the effects of controls can be indirect, by infl uencing competition. Even this seemingly indirect control can have further levels of complexity because competition between algae and corals can be direct (e.g., over-growth) or indirect (e.g., preemption of substrate). High herbivory (via physical removal) also acts indirectly on fl eshy algae through reduced competitive ability, whereas lowered herbivory and elevated nutrients also indirectly inhibit or control corals and coralline al-gae by enhancing fl eshy algal competition. Other ecologically important bottom-up fac-tors, such as reduced light, abrasion, allelopathy, disease vectoring, and sediment smoth-ering, also result from indirect side effects of fl eshy algal competition. These factors tend to selectively eliminate the long-lived organisms in favor of weedy fast-growing species, thereby reducing desirable complexity and biodiversity.
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The decline and potential recovery of Caribbean reefs has been the subject of intense discussion and is of great interest to reef ecologists and managers. The recent return of Diadema antillarum sea urchins at some Caribbean locations and the concomitant changes in coral cover and recruitment. provide a new perspective on the reversibility of Caribbean coral reef decline. This study examined the influence of recovering populations of Diadema and the subsequent formation of dense urchin zones on the growth and density of newly settled juvenile scleractinian corals. In these urchin zones, where Diadema graze algae, we documented higher growth rates of juvenile corals, and higher densities of small juvenile recruits (likely to be important precursors to reef recovery). Coral survivorship was higher for juvenile corals living in urchin versus algal zones. Roughly 83% of the juvenile corals in urchin zones survived over the 2 yr period of the study, while similar to 69% survived in the algal zones. Corals in the urchin zones increased in major diameter by an average of 75 +/- 7% from 2001 to 2003 versus 24 +/- 4% for corals in the algal zones during the same time period. The relatively abrupt decrease in macroalgal cover and the signs of increasing coral cover along the north coast of Jamaica following the return of Diadema, reported here and by other authors, suggest that these reefs have undergone rapid phase shifts, rather than being constrained to alternate stable states. In the Caribbean, it appears that Diadema are effective at enhancing scleractinian coral recruitment and growth and thus could be used as an important manipulative tool for returning reefs to a coral dominated state, especially on reefs that are severely overfished.
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The Atlantic and Gulf Rapid Reef Assessment (AGRRA) sampling strategy is designed to collect both descriptive and quantitative information for a large number of reef vitality indicators over large spatial scales. AGRRA assessments conducted between 1998 and 2000 across a spectrum of western Atlantic reefs with different histories of disturbance, environmental conditions, and fishing pressure were examined to reveal means and variances for 15 indicators. Twenty surveys were compiled into a database containing a total of 302 benthic sites (249 deep, 53 shallow), 2,337 benthic transects, 14,000 quadrats, 22,553 stony corals. Seventeen surveys contained comparable fish data for a total of 247 fish sites (206 deep, 41 shallow), 2,488 fish transects, and 71,102 fishes. Shallow (≤ 5 m) reefs were dominated by A. palmata, a good proportion of which was standing dead, while deep (>5m) reefs were nearly always dominated by the Montastraea annularis species complex. Fish communities were dominated by acanthurids and scarids with seranids making up less than 1% of the fish seen on shallow reefs and 4% on deep reefs. AGRRA benthic and fish indicators on deep reefs showed the highest variation at the smallest spatial scale (∼0.1 km), with recent mortality and macroalgal canopy height displaying the largest area and subregional scale (∼1-100 km) variation. A mean live coral cover of 26% for the 20 survey areas was determined for the deep sites. Significant bleaching and disease-induced mortality of stony corals associated with the 1998 (El Niño-Southern Oscillation) ENSO event were most apparent in the western Caribbean and Bahamas subregions and the Montastraea annularis complex was the most heavily impacted. The overall low number of sightings for larger-bodied groupers and snappers (∼< 1/100 m2 ) as a whole suggest that the entire region is overfished for many of these more heavily targeted species. More remote reefs showed as much evidence of reef degradation as reefs more proximal to human coastal development. Characterizing present-day reef condition across the region is a complex problem since there are likely multiple sources of stress operating over several spatial and temporal scales. Not withstanding the many limitations of this analysis, the value of making multiple observations across multiple spatial scales that can approximate the "normal" state for the region today is still very high.
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