Characterization and evaluation of coral reefs around Yap Proper, Federated States of Micronesia

ORI GIN AL PA PER

Characterization and evaluation of coral reefs aroundYap Proper, Federated States of Micronesia

Peter Houk • David Benavente • Vanessa Fread

Received: 27 July 2011 / Accepted: 26 April 2012 / Published online: 1 June 2012� Springer Science+Business Media B.V. 2012

Abstract This study addresses the coupled themes of science and conservation by

characterizing and evaluating the coral reefs around Yap, Federated States of Micronesia.

Reef types, and the inherent environmental regimes they constitute, were found to be good

predictors of distinct modern assemblages, with minimally overlapping species occur-

rences. Corals from inner and channel reefs were twice as large and assemblages were half

as diverse compared with outer reefs, while food-fish were both larger and more diverse on

outer and channel reefs compared with inner. While distinctions were predictable, the

magnitude of ecological change along a gradient of inner, channel, to outer reefs was

higher than expected, suggesting that human influences are quantifiable. Therefore, an

evaluation process was conducted to determine the spatial trends in reef ‘condition’,

defined within by ecological metrics. ‘Condition’ was highest for reefs associated with

a priori defined high conservation value for varying reasons: successful fisheries man-

agement, critical habitat determination, and high resiliency potential. Regression analyses

highlighted that a two-variable model which interactively incorporated proxies to fishing

and pollution, as well as a proxy for hydrodynamic flushing potential, explained 40 % of

the variance in ‘condition’. Collectively, the results are used to evaluate the current status

of reef assemblages, and to point out future conservation priorities.

Keywords Yap � Coral-reef assemblages � Conservation � Fish assemblages � Marine

conservation areas � Status

P. Houk (&)Pacific Marine Resources Institute, Saipan, MP 96950, Northern Mariana Islandse-mail: [email protected]

D. BenaventeCommonwealth of the Northern Mariana Islands Coastal Resources Management Office, Saipan, MP96950, Northern Mariana Islands

V. FreadYap Community Action Program, Colonia, Yap, FM 96943, Federated States of Micronesia

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Biodivers Conserv (2012) 21:2045–2059DOI 10.1007/s10531-012-0296-0

Introduction

The numerous islands that comprise the Federated States of Micronesia (FSM) contain

coral-reef resources that are of global significance in terms of their biological diversity and

value, yet they remain among the most poorly documented despite their heavy economic

and subsistence use (Johannes 1978; Houk et al. 2011). Accordingly, a common challenge

for improving local monitoring and management programs is to first understand the status

and distribution of coral-reef resources upon which predictive relationships between

environmental drivers and ecological patterns can be developed (Houk and van Woesik

2010; Zvuloni et al. 2010; Pittman and Brown 2011). Initial efforts to characterize FSM

reefs consisted of rapid ecological assessments that were mainly focused upon docu-

menting biological diversity across the region (Turak and DeVantier 2005; Donaldson

et al. 2006; Allen 2007; Houk and Starmer 2007). While these studies identified areas of

unique and high richness for marine protected area consideration, species checklists and

qualitative datasets are limited with respect to their repeatability, and thus, ability to assess

change through time. As the region moves forward in defining and assessing conservation

goals, quantitative relationships are imperative for determining rates of change and

acceptable thresholds (Nichols and Williams 2006; Houk et al. 2010). Through efforts such

as the present study, regional monitoring programs continue to improve their quantitative

baseline; however, one additional challenge that remains is translating the ensuing science

for its practical use.

Numerous studies have defined ecological criteria of coral-reef assemblages upon which

‘condition’, ‘conservation value’, or ‘health’ was interpreted (Houk et al. 2005; Rodgers

et al. 2010; Oliver et al. 2011). While many indicators clearly exist (Jameson et al. 2001;

Cooper et al. 2009), the greatest attention has been afforded to metrics describing benthic,

coral, and fish assemblages due to their tangibility, sensitivity to human influences (Fab-

ricius et al. 2005), low-cost-and-capacity sampling, and translation into monetary value

(Cesar and van Beukering 2004; Brander et al. 2007). However, the doctrine pertaining to

their practical integration and overall evaluation remains lacking, and somewhat confusing.

For instance, similarly collected coral and fish assemblage data have been used to rec-

ommend protected area networks that are focused upon critical habitat for reef-fish pro-

tection (Mumby 2006), areas of high biological richness (Roberts et al. 2002), and

aggregation centers of apex predators (Heithaus et al. 2008). Clearly the perspective and

analytical approach taken can drive management recommendations, yet, what approach is

most relevant for ecosystem-based conservation needs?

Here, we build upon the coupled themes of coral-reef ecology and conservation by pro-

viding a characterization and evaluation of the reef habitats surrounding Yap Proper, FSM. Yap

is one of the few places in Micronesia where traditional marine tenure remains; however,

improving fishing technology, growing infrastructure on land, and more reliance upon a cash

economy represent threats that are not encompassed by traditional forms of management

(Johannes 1978; Kronen and Tafileichig 2008). Indeed, declines in Yap’s fishery status through

time have been attributed to the mixing of ‘new’ technology and ‘traditional’ management

(Graham 1992; Houk et al. 2011). In order to improve upon this situation, governmental and

non-governmental organizations are rooted in enhancing the communities’ knowledge of their

coral-reef ecosystems, yet transferrable science remains limited. Thus, the goals of the present

study include translating the scientific knowledge generated into compelling insight, taking an

objective and repeatable approach for future applicability.

We begin by examining modern assemblages with respect to major habitat classifica-

tions. Existing rapid ecological assessments suggested that wave exposure, and/or major

2046 Biodivers Conserv (2012) 21:2045–2059

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reef types, best predicted the distribution of coral and fish assemblages, as well as species

richness patterns (Allen 2007; Houk and Starmer 2007). Here, we formally determine

habitat preferences, and quantify the nature and magnitude of ecological separation across

reef types. We next examine several key attributes of the coral and fish assemblages,

including diversity and abundance trends, differential resistance/recovery from Acanth-aster planci predation, and unique species occurrences. These site-attributes were initially

defined in the REA assessments to indicated the presence of ‘high conservation value’

reefs, a term we incorporate here to indicate reefs that are under successful management, as

well as those that are associated with favorable environmental settings that promote

ecosystem resiliency, or represent critical habitat for species of special concern (Mumby

2006; Nystrom 2006; Graham et al. 2011). To examine the broader utility of this definition,

we defined a univariate index of ‘condition’ by integrating several, sufficiently uncorre-

lated metrics of the modern assemblages, and determine its ability to predict previously

defined high conservation value reefs. Building upon encouraging results, exploratory

regression models were constructed to examine a gradient of human influences and

environmental regimes that predict the condition of reefs across Yap.

Methods

Location and survey design

Yap is the westernmost state of the FSM, encompassing Yap Proper, the main island, and

14 outlying atolls (Fig. 1). Yap Proper has the lowest human population among the four

FSM main islands, with 7,400 residents spread over 10 municipalities (Yap Branch Sta-

tistics Office 2002). Quantitative coral, fish, and macroinvertebrate data were collected at

15 stations previously established as part of a rapid ecological assessment (Houk and

Starmer 2007). Representative sites were selected in each of three defined reef types: (1)

inner reefs, also termed ‘blue holes’, which are isolated deep water zones within the lagoon

system (sites 8, 14, 17, and 19, Fig. 1), (2) channel reefs where flushing and tidal

exchanges are maximal (sites 1, 2, 4, 5, 12, and 13), and (3) outer reefs along the barrier

complex (sites 3, 6, 11, 15, and 16). Surveys were conducted at the 5 m depth contour for

inner and channel reefs situated in calm waters, and at the 8 m contour for outer exposed

reefs. Employing single-depth investigations maximized our spatial extent of study, while

focusing upon the reef zones that resided under minimal environmental control due to light

limitation and wave energy (Sheppard 1982; Yentsch et al. 2002; Cooper et al. 2009). For

wave-sheltered channel and inner reefs, light levels rapidly decrease due to higher par-

ticulate matter and plankton growth in the productive waters adjacent to land. In contrast,

wave-energy is the strongest driver of shallow assemblages on outer reefs, and the 8 m

contour was selected to balance the influence of wave energy and light limitation.

Survey methods

Coral assemblages were investigated using a standard quadrat-based technique, similarly

used by Houk and Starmer (2007). Eight, 1 m2 quadrates were haphazardly tossed on the

coral reef substrate while swimming between two GPS-identified survey points that

marked each station, spaced *300 m apart. All coral colonies whose center-point resided

inside the quadrat were identified and measured. Coral taxonomy followed Veron (2000).

Abundances, population densities, and geometric diameters were calculated assuming

Biodivers Conserv (2012) 21:2045–2059 2047

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colonies were circular in nature. These methods provided measurements of 80–240 col-

onies per site, with a mean of 157, and total of 2,364. Diversity and evenness metrics were

calculated using species-level data, while multivariate analyses used groupings of func-

tional similar species complexes (e.g., Favia favus, F. matthaii, and F. speciosa) to provide

representative weighting for functionally-similar coral groups. Finally, quadrat data from

2007 were incorporated to examine the nature and extent of recovery from Acanthasterplanci disturbance along Yap’s southwestern coastline.

Fig. 1 A map of Micronesia (inset) and Yap Proper with survey stations indicated by numbers. Circle sizeindicates relative coral-reef ‘condition’ scores (‘‘Methods and Results’’ sections). The star refers to theorigin of a recent Acanthaster planci outbreak, as defined by peak starfish densities (‘‘Results’’ section)


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Fish assemblages were surveyed using twelve stationary-point-counts (SPC’s) spaced at

equal intervals between the identified survey points (Bohnsack and Bannerot 1986). During

each SPC the observer recorded the name and size of all food-fish within a 5 m circular

diameter for a period of 3 min. Species identifications were made for the majority fish,

with two notable exceptions being small-bodied acanthurids and scarids which were

mainly grouped. Length estimates were converted to biomass using documented conver-

sion coefficients (www.fishbase.org). These methods provided measurements of 90–551

individual fish per site, with a mean of 248, and total of 3,725. Prior to some analyses, this

study distinguished between large-and-small bodied species for most fish families, which

were defined by a reported reproductive size threshold of 25 cm. Size at maturity estimates

were collected using the fishbase life history interactive tool (www.fishbase.org). Similarly

noted above, diversity estimates used the highest taxonomic resolution available, while

multivariate analyses used groupings of functional similar species complexes.

Macroinvertebrate abundances were estimated from five replicate 5-min swims con-

ducted between the two established survey points. Counts were made while following the

depth contours noted above.

Data analyses

Coral and fish assemblages were first assessed to determine habitat preferences using a

standard, multivariate approach. Data were aggregated at the site-level by taking the means

of functionally-similar species complexes from replicate quadrat, or SPC, observations.

Bray-Curtis similarity coefficients were calculated between each pair of sites, and resultant

relationships were visualized in non-metric, multi-dimensional scaling plots (MDS,

Anderson et al. 2008). Significance was assessed from PERMANOVA tests that are

analogous to ANOVA’s, but conformed to meet multivariate requirements (Anderson et al.

2008). PERMANOVA tests are evaluated based upon a pseudo F-statistic, and subsequent

t-statistics defining post hoc comparisons among groups. Vector overlays highlight corals

and fishes that had the greatest influence on data dispersion, based upon Spearmen cor-

relation coefficients (P [ 0.5) with the axes.

Univariate comparisons of numeric density, percent coverage, and biomass were next

conducted for several taxa to better describe coral and fish habitat partitioning. If

assumptions of normality and heterogeneity were met with or without transformations,

standard ANOVA and post hoc tests were used, else non-parametric testing was conducted

(Kruskal–Wallis rank tests). In the case of food-fish abundances, specific examination of

two species of concern, the Napoleon wrasse (Cheilinus undulatus) and the bumphead

parrotfish (Bolbometopon muricatum), were conducted to determine if habitat preferences

existed for varying life stages. In order to assess the present distribution trends in

Acanthaster planci densities, non-parametric testing was conducted to examine spatial

differences, as data were strongly non-normal due to the absence of predator starfish at

many sites. Finally, in order to evaluate change in coral colony-size distribution between

2007 and the present, Kolmogorov–Smirnov (K–S) tests were preferably used as they

investigate differences between two sets of cumulative frequency data.

Coral-reef ecosystem condition

The premise behind developing a single measure of coral-reef ecosystem condition was to

provide a comprehendible, repeatable, and rational integration of the data. Our goal was to

incorporate the maximum number of ecological metrics known to be sensitive to localized


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http://www.fishbase.org

http://www.fishbase.org

stressors, while ensuring they were not highly co-linear. Reef condition was defined by

four measures of the coral assemblages (species richness, cover, multivariate dissimilarity,

and colony-size distributions), as well as two measures of the fish assemblages (total

biomass and Shannon–Weaver evenness). Correlation testing revealed sufficient inde-

pendence, with coefficients ranging from 0.3 to 0.53. While coral cover, species richness,

and fish biomass are easily interpretable, others are further described. Multivariate dis-

similarity is defined as the mean, multivariate distance between each replicate coral

quadrat, and the overall site-mean, or centroid point (Anderson et al. 2008). After strati-

fication by reef type, increases in multivariate dissimilarity translate to greater assemblage

heterogeneity, beneficial for resiliency and function (Rosenfeld 2002; Elmqvist et al. 2003;

Nystrom 2006). Both the skewness and kurtosis of coral colony-size distributions have

been used as indicators of status (Bak and Meesters 1998; McClanahan et al. 2008; Houk

and van Woesik 2010), representing the proportion of juveniles compared to adults, and the

dominance of any particular size class. For coral assemblages, less skew and kurtosis are

indicative of reefs under lower human influence. Prior to integration with other metrics,

skewness and kurtosis values were standardized and averaged to provide a single, repre-

sentative measure of colony-size distributions. Finally, to establish a single value for

overall condition, remaining metrics were standardized, a constant value was added to

make all numbers positive integers, and the overall mean was calculated.

Based upon the exploratory rapid ecological assessments conducted in 2007, three reefs

were considered to have relatively high conservation value: an inner reef where juvenile

Napoleon wrasse densities were maximal, a channel reef where community-based, no-take

fishing policies exist (Nimpal marine conservation area), and an outer reef where recovery and/

or resistance from Acanthaster planci disturbances was maximal. In order to evaluate the

sensitivity of our ecological condition metric, a pairwise t-test was conducted to examine

condition between these sites (n = 3) and all others (n = 12). Prior to testing, condition values

were normalized by reef type to account for the inherent environmental regimes they constitute.

We last explored the physical predictors of condition across Yap. Mixed regression

modeling was conducted to evaluate the extent that proxies to fishing pressure, land-based

pollution, flushing rates, and habitat size could predict condition. Fishing pressure was

estimated by the distance from all population centers that have traditional access rights to

the site being evaluated, multiplied by the human population. Pollution proxies were

estimated as the area of urbanized or barren land in the adjacent watersheds based upon US

Forest Service land use GIS layers (http://www.fs.fed.us). Habitat size was estimated for

channel sites only by measuring polygons drawn a satellite image. Finally, hydrodynamic

flushing rates were estimated for inner reefs only by measuring the linear distance to the

nearest channel mouths. All independent variables were standardized, and exploratory

models were generated using R (R Core Development Team 2005). For this analysis, the

no-take fishing preserve was omitted, as successful management is anomalous to the

natural gradients being investigated. Residual normality and independence were examined

for all significant models.

Results

Reef types, and the inherent environmental regimes they constitute, were found to be good

predictors of distinct coral and fish assemblages, with minimally overlapping species

occurrences. Porites corals were strongly associated with inner and channel reefs, as

massive species attained largest sizes on inner reefs, Porites cylindrical was common to


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http://www.fs.fed.us

both, and all other major functional Porites growth forms were more frequent in channels

(Figs. 2a, 3). Outer reef assemblages were distinct from others (t statistic [ 2.5, P \ 0.01,

PERMANOVA comparisons, Fig. 2a), due mainly to higher abundances of Acropora,

Pocillopora, and faviid corals. Accordingly, species richness was highest on outer reefs

Reef TypeChannelInnerOuter

1

11

12

13

14

15

16 17

19

2

3

4

5

6

8

Acropora arborscentAcropora corymbose/tabulate

Cyphastrea

Echinopora

Favia stelligeraGalaxea

Goniastrea

Hydnophora rigida

Leptastrea

Leptoria

Millepora

Platygyra

Pocillopora

Porites cylindrica

Porites rus

Scapophyllia

Stylocoeniella

Stylophora

2D Stress: 0.08

1

1112

13

2

4

5

14

17

19

8

15

16

3

6

BatfishBolbometopon muricatum

Cheilinus undulatus

Large-bodied parrotfish

SharkSmall-bodied acanthurids

Small-bodied grouper

Small-bodied parrotfishSoldierfish

Sweetlips

TrevallyTriggerfish

2D Stress: 0.1

(a)

(b)

Figs. 2 a, b. Multi-dimensional scaling plots highlighting significant differences in (a) coral and (b) fishassemblages in accordance with reef type. Vectors highlight corals and fish that had the greatest influence ondata dispersion, based upon Spearman’s rank correlation coefficients (P [ 0.5)


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(9.4, 4.9, and 4.2 species per quadrat, respectively for outer, channel, and inner, F-sta-

tistic [ 3.1, P \ 0.01 for comparisons against outer reefs, ANOVA and post hoc tests),

while mean colony size was lowest (7.6, 11.3, and 18.8, respectively, F-statistic = 2.9,

P \ 0.05 for outer versus inner comparisons only). Larger colony sizes equated to the

highest percent coral cover on channel reefs, where expanses of Porites rus, P. cylindrica,

and other massive Porites species existed, as well as infrequent stands of large Pavona,

Scapophyllia, Millepora, staghorn Acropora, and branching Hydnophora rigida. In sum-

mary, large gradients existed for coral assemblage composition across reef types, as several

measures such as diversity, evenness, and numeric density were maximal on outer reefs

where environmental regimes appear to be most benign (i.e., high water exchange rates,

least influence of extreme temperature regimes, moderate wave energy, and furthest

proximity from human influence), yet coverage remained maximal on inner and channel

reefs.

Food-fish assemblages showed differing patterns compared with corals. Outer and

channel reefs had food-fish assemblages that were most similar, while inner reefs were

unique (t statistic [ 2.1, P \ 0.01, PERMANOVA comparisons, Fig. 2b). These trends

were driven by declining abundances of all major fish, rather than any habitat-specific

shifting of occurrences (Fig. 4). In support, mean population density (29.5, 18.7, and 12.6

fish per SPC for outer, channel, and inner, respectively) and biomass (3.7, 2.0, and 0.4 kg

per SPC, respectively) followed a similar decreasing trend (P \ 0.05 for all pairwise

comparisons, ANOVA and post hoc tests). When considered at the trophic level, expected

increases were noted for all functional groups along a gradient of inner, channel, to outer

reefs (Fig. 5). However, the magnitude of change was much larger than expected, as

biomass was nearly 10 times higher on the outer compared with inner reefs, attributed

mainly to the reduction of primary and tertiary consumers.

Fig. 3 Percent cover and densityof corals that were mostinfluential in distinguishingbetween reef types based uponmultivariate dispersion (SE bars)


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Closer examination of two species of special concern revealed contrasting findings. For

the Napoleon wrasse, Cheilinus undulatus, densities of juvenile fish were significantly

greater on inner reefs (P \ 0.05, Kruskal–Wallis), especially at site 17 (P \ 0.05, post hoc

Fig. 4 Biomass and density of fish that were most influential in distinguishing between reef types basedupon multivariate dispersion (SE bars)

Fig. 5 Biomass of fish by trophic level for inner, channel, and outer reefs (SE bars). Stacked bars representmean primary, secondary (benthivores), secondary (planktivores), and tertiary consumer abundance


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comparisons), with a mean of nearly one fish per replicate SPC (Fig. 6). However, biomass

appeared to be highest on channel and outer reefs (P = 0.06, Kruskal–Wallis). For the

bumphead parrotfish, Bolbometopon muricatum, no trends in population densities were

noted, however biomass appeared to be higher at among channel reefs (P = 0.08, Kruskal–

Wallis).

Finally, local observations of high and fluctuating Acanthaster planci densities have

been observed since 2009 (sites 16–11, pers. obs. VF). The present macroinvertebrate

surveys found high predator starfish densities at the southwestern tip of Yap compared with

elsewhere (mean of 7.8/5-min swim, site 16; mean of 0–0.6/5-min swim, all other sites;

P \ 0.001, Kruskal–Wallis). Despite the high density, and potentially representing a

source population for the southwestern coastline, the outer reef at Yap’s southern point

(site 16) showed no significant changes in coral cover or assemblage heterogeneity since

2007, suggesting high resistance and/or recovery. Also notable, there were no starfish

recorded in the no-take, Nimpal marine conservation area (MCA) (site 13) that is centrally

located along this coastline. Here, a significant increase in mean colony size since 2007

(P \ 0.01, K–S tests, Fig. 7), a non-significant change in assemblage heterogeneity, and

high fish biomass were reported (Table 1).

Estimates of coral-reef condition (i.e., ecological metrics) were comparatively higher

for sites attributed with high conservation value (t statistic = 2.95, P = 0.01), although

individual metrics varied (Table 1). The inner reef where maximal Napoleon wrasse

densities existed held high coral assemblage heterogeneity with many large colonies, high

fish richness, and moderate levels of other metrics. The outer reef with high resistance/

recovery had the highest fish biomass, along with relatively high values for all other

metrics. The channel reef with successful MCA establishment also had high fish biomass

and coral coverage, but relatively low coral richness and fish evenness, potentially due to

natural characteristics.

Predictors of condition

Given the sensitivity of condition estimates in identifying reefs of high conservation value,

predictive regression models were built to explore relationships across Yap. A two variable

Fig. 6 Biomass and density of Cheilinus undulatus at individual sites. Inner reefs held significantly higherdensities of small fish, and site 17 had highest densities, while biomass appear to be greater on channel andouter reefs


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model that included one interactive term describing proxies to fishing and pollution

(slope = -0.12 ± 0.04), as well as second term for a proxy to hydrodynamic flushing rate

(slope = 0.78 ± 0.41), explained 40 % of the variance associated with condition estimates

(P = 0.04). In summary, this analysis predicts that sites closest to population centers and

urbanized/barren land, with poor flushing potential, consistently had the lowest condition

(Fig. 1).

Discussion

This study reports predictable distributions of fish and coral resources around Yap that

were driven by both natural environmental regimes and human influences. While several

metrics such as coral diversity, evenness, and fish biomass are well known to decrease

along a gradient of environmental selectivity (i.e., from outer reefs with maximal flushing,

minimal temperature extremes and turbidity variation, to inner reefs with minimal flushing,

influential tidal regimes, temperature extremes, and higher turbidity; Gust et al. 2001;

Lecchini et al. 2003; DeVantier et al. 2006; Houk and Starmer 2010), the magnitude of this

gradient has received less attention. In comparison to a remote coral reef ecosystem in the

central Pacific where fish biomass was *2.5 times higher on outer compared with inner

atoll reefs (Friedlander et al. 2010), this study disproportionally reports four times higher

(a)

(b)

Fig. 7 Coral colony size comparisons between 2007 and 2011 for (a) sites along the southwestern coastline(16, 15, 12, and 11, Fig. 1) where high Acanthaster planci populations were noted, and (b) the Nimpal MCAfishery closure (site 13) where no starfish were observed


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biomass on channel compared with inner reefs, and eight times higher biomass on outer

reefs.

The disproportional reduction of all major fish groups moving from outer to inner reefs

intuitively suggests that implications for coral assemblages might exist, assuming that top

down influences in the marine food web are influential (Estes et al. 2011). However,

limited evidence exists from remote reef areas to provide a similar context. While com-

parisons between ‘pristine’ and more disturbed reef ecosystems continue to improve our

understanding of shifting coral assemblages (Sandin et al. 2008), limited research exists to

provide details into the magnitude of naturally-occurring gradients under varying human

influences. Here, we noted an expected increase in Porites (and heterotrophic species)

dominance moving from exposed outer reefs to protected, channel/inner reefs, yet the

multivariate analysis indicated distinctive, minimally-overlapping species occurrences. We

hypothesize that while reef types serve as proxies for environmental separation, through

time, the magnitude of coral species overlap between reef types has been decreasing with

human influence. In support, Fabricius (2005) summarized that reduced species richness,

increased dominance by tolerant species, and reduced evenness of coral assemblages

becomes evident along a gradient of terrestrial influence, suggestive of enhanced assem-

blage separation through time.

Table 1 Mean values of the ecological metrics used to evaluate coral-reef condition. Metrics were stan-dardized to provide equal weighting, a constant value was added to make all numbers positive integers, andthe overall mean is reported under ‘‘condition’’ (within each reef type). In order to compare condition acrossall sites, values were standardized with respect to their reef type. See ‘‘Methods’’ section for further details

Site Coral

species

richness

(per m2)

Coral

multivariate

dissimilarity

Percent

coral

cover

Coral

skewness

and

kurtosis

Fish

biomass

(kg per

SPC)

Fish

evenness

Condition

(standardized

within each reef

type)

Condition

(standardized

across all reef

types)

Inner reefs

8 6.5 38.7 54.8 (5.0) (31.0) 0.7 1.0 2.36 1.98

14 3.9 39.9 50.2 (4.4) (24.5) 0.3 0.9 2.25 1.53

17 2.1 53.0 43.0 (2.5) (6.4) 0.5 1.1 2.71 3.4

19 4.1 37.0 54.6 (3.8) (16.5) 0.3 0.5 2.14 1.09

Channel reefs

1 2.6 33.3 65.1 (4.1) (18.0) 1.1 1.1 2.63 0.47

2 4.4 72.2 45.1 (3.3) (12.7) 3.6 1.3 3.26 2.27

4 5.3 51.0 61.0 (3.5) (14.2) 0.8 1.0 2.86 1.13

5 7.3 81.8 74.2 (4.5) (24.4) 1.6 1.2 3.32 2.44

12 5.8 104.5 78.2 (3.6) (18.5) 1.5 1.2 3.58 3.17

13 3.9 102.3 79.6 (4.3) (22.7) 3.1 1.0 3.35 2.52

Outer reefs

3 9.6 12.4 65.9 (3.6) (15.9) 5.3 1.1 3.44 2.26

6 9.5 16.8 69.1 (4.5) (30.3) 1.4 0.9 2.7 0.81

11 8.1 54.6 66.8 (4.0) (19.8) 2.0 1.2 3.31 2.01

15 10.6 14.7 66.4 (3.9) (23.3) 1.7 1.0 3.02 1.44

16 9.1 26.9 75.2 (3.4) (16.0) 8.4 1.4 4.06 3.48


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Concomitant to observed fish and coral assemblage trends, this study also reported

that proxies to fishing and pollution were significant predictors of reef condition, indi-

cating that despite a small human population of 7,400, or 74 individuals km-2, human

footprints are evident. In fact, regression analyses highlighted that localized stressors

acted synergistically in predicting coral-reef condition (i.e., the best-fit model contained

a single, interactive term for proxies to fishing pressure and pollution). Yet, further

insight into their partial influence is desirable because management strategies for pol-

lution and fishing differ. Building longer-term and larger-scaled datasets across gradients

of water quality and fish assemblages that tract the ecological responses of reef assem-

blages through time represents a useful means towards predicting the likely outcomes of

management scenarios, and incorporating gradient analyses into long-term monitoring

frameworks is one ideal approach (Houk et al. 2010; Wilson et al. 2010; McClanahan

et al. 2011).

While distilling complex ecological knowledge into a single, condition metric might be

regarded as overly simplistic, more complex approaches towards evaluating reef status

should substantially improve our prediction of patterns to be preferentially considered

(Balasubramanian 1997). The Nimpal MCA is one form of management that benefitted

from the spatial interpretation of condition. High conservation value noted in 2007 was

mainly due to strong community-based support for management, as ecologically, insight

based mainly upon species richness data showed that non-unique assemblages existed

(Allen 2007; Houk and Starmer 2007). However, 4 years later, after formalizing their no-

take MCA, condition is now second highest among channel reefs despite having the

smallest habitat size. Thus, due to a strong social acceptance, this reef has exceeded its

natural ecological expectations, relative to human influences that currently exist, and

confirms the importance of including social factors into conservation planning (Walmsley

and White 2003). Beyond increasing fish populations, growing evidence supports that

conservation of numerous key ecological functions inside fisheries closures. Here, the

negative influences from predator starfish activity along Yap’s southwestern coastline

appeared diminished within the MCA, corroborating similar reports from closures else-

where along the Great Barrier Reef (McCook et al. 2010).

Finally, identifying where and why resiliency exists is a central focus for resource

management (Wooldridge et al. 2005; Hughes et al. 2010). We ironically purport that high

recovery and predator starfish abundance at the southern tip of Yap (site 16) may be a

consequence of the same local hydrodynamic process. Circulation eddies are known to

form in the lee of exposed islands and have been documented to benefit recruitment and

settlement (Black et al. 1995; Mace and Morgan 2006; Burgess et al. 2007). Thus, the high

recovery noted here may be aided by the favorable oceanographic and physical setting that

exists.

We conclude that a simple, thoughtful approach, combining several robust measures

coral and fish populations provided a useful snapshot of Yap’s coral reefs. Through time,

quantitative trends can improve the basis for balancing resource integrity and sustainability

with socioeconomic needs.

Acknowledgments Financial support for this project provided by the National Oceanic and AtmosphericAdministration, general coral reef conservation program, award NA05NMF4631049. The authors aregrateful to the staff of the Yap Community Action Program and the numerous community representativesthat assisted with logistics and fieldwork. Two anonymous reviewers and the topic editor provided con-structive input that greatly benefitted our manuscript.


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Characterization and evaluation of coral reefs around Yap Proper, Federated States of Micronesia

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