Accepted Manuscript Contrasting responses of coral reef fauna and foraminiferal assemblages to human influence in La Parguera, Puerto Rico L.M. Oliver, W.S. Fisher, J. Dittmar, P. Hallock, J. Campbell, R.L. Quarles, P. Harris, C. LoBue PII:
S0141-1136(14)00077-4
DOI:
10.1016/j.marenvres.2014.04.005
Reference:
MERE 3882
To appear in:
Marine Environmental Research
Received Date: 4 December 2013 Revised Date:
7 April 2014
Accepted Date: 13 April 2014
Please cite this article as: Oliver, L.M., Fisher, W.S., Dittmar, J., Hallock, P., Campbell, J., Quarles, R.L., Harris, P., LoBue, C, Contrasting responses of coral reef fauna and foraminiferal assemblages to human influence in La Parguera, Puerto Rico, Marine Environmental Research (2014), doi: 10.1016/ j.marenvres.2014.04.005. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
1 2 3 4 5 6 7 8 9 10
Contrasting responses of coral reef fauna and foraminiferal assemblages to human influence in La Parguera, Puerto Rico
11 12 13 14 15 16 17 18 19 20 21 22
2
University of South Florida, 140 7th Ave. S, St. Petersburg, FL 33701
3
U.S. Environmental Protection Agency, Region 2, New York, NY 10007-1866
23
Coral reef biota including stony corals, sponges, gorgonians, fish, benthic macroinvertebrates and
24
foraminifera were surveyed in coastal waters near La Parguera, in southwestern Puerto Rico. The
25
goal was to evaluate sensitivity of coral reef biological indicators to human disturbance. Proxies
26
for human disturbance were measured as distance to town (DTT) and rankings of a low-level
27
sediment contamination gradient analyzed from a previous study. Contaminant rank and DTT
28
showed that percent mud, stony coral taxa richness, reef rugosity, and numbers of invertebrates
29
and sponges were higher at sites closer to human disturbance, but a foraminiferal assemblage
30
index was significantly lower at sites with higher proxies for human disturbance. Fish indicators
31
showed no significant relationships with human activity, but associations between fish community
32
measures and certain measures of stony corals, gorgonians and sponges were found. Contrasting
33
responses between foraminifera and reef organisms may be due to greater exposure and sensitivity
34
of foraminifera to sediment contaminants.
1
Oliver, L.M., 1Fisher, W.S., 1Dittmar, J., 2Hallock, P., 1Campbell, J., 1Quarles, R.L. 1Harris, P. and 3LoBue, C. 1
SC
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U.S. Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Gulf Ecology Division, 1 Sabine Island Drive, Gulf Breeze, FL 32561-5299
M AN U
Corresponding Author: [email protected] 850 934-2470
Key Words: Coral reef, human disturbance gradient, sediment contaminants, stressors
AC C
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Abstract
1
ACCEPTED MANUSCRIPT
35 36
1. Introduction La Parguera, Puerto Rico hosts a diverse and complex tropical marine ecosystem characterized by mangrove islands, seagrass beds, macroalgal beds, stony corals, gorgonians,
38
sponges and associated fish and invertebrate macrofauna (Pittman et al., 2010; Ballantine et al.,
39
2009). Calcareous structures formed by stony coral reefs provide shoreline protection and
40
support a complex ecology, productive fisheries, and aesthetically-pleasing recreational
41
opportunities for local residents as well as seasonal tourists. Historically, the La Parguera
42
nearshore stony coral reef structure was dominated by Acropora sp. with proportionally more
43
Montastraea sp. at increasing depth (Acevedo et al., 1989), but since the late 1980s, both of
44
these important reef-building species have experienced severe losses (Gardner et al., 2003).
45
Acropora palmata and A. cervicornis have nearly disappeared and the Montastraea species
46
complex (M. faveolata, M. annularis, and M. cavernosa) has also declined from effects of
47
bleaching and disease (Goenaga et al., 1989; Garcia-Sais et al., 2008; Ballantine et al., 2009).
48
Loss of reef resources is well-documented, but less understood are the relative contributions of
49
different stressors to stony coral decline, and how management efforts may optimally work
50
toward decisions that restore the reefs to their historical condition. Understanding which
51
anthropogenic factors have the greatest impact allows prioritization of resources for
52
management action and enforcement, which is essential to ensure delivery of critical reef
53
services (Fore et al., 2009; Bradley et al., 2010).
SC
M AN U
TE D
EP
AC C
54
RI PT
37
While ocean warming, diseases and storms have reduced stony coral condition on a
55
regional scale, anthropogenic changes on land may have compromised Puerto Rico reef habitats
56
through increased runoff of sediments, nutrients and chemical pollutants (Warne et al., 2005;
57
Weber et al., 2006; Richmond et al., 2007). Clearing land for agriculture and municipal
58
development increases the amount of impervious surfaces and reduces the natural barriers to 2
ACCEPTED MANUSCRIPT
watershed runoff, both leading to greater sediment and entrained chemical pollutants entering
60
the marine environment (Rogers, 1990; Fabricius, 2005). Guánica Bay, to the east of La
61
Parguera, has been inundated over the last several decades with sediment from upstream
62
activities including municipal development, road construction and agriculture, particularly
63
coffee farming on the mountain ridges (WMP, 2008). Hydrologic alterations for irrigation and
64
power generation have increased flow to Guánica Bay, where exiting water with entrained
65
sediment generally flows westward in the prevailing current towards La Parguera’s coral reefs
66
(Kaye, 1959).
SC
RI PT
59
Non-point runoff from the area around La Parguera is also a source of sediments,
68
nutrients and contaminants. With a population of approximately 30,000 people, La Parguera is
69
not a large city but is undergoing new development in close proximity to the coast. Analysis of
70
sediment cores collected near La Parguera provided evidence of a human signature as
71
sedimentation rates decreased in a seaward direction, and terrestrial sediment accumulation
72
increased in back-reef sediment compared to fore-reef sediment (Ryan et al., 2008). Ramos-
73
Scharrón (2007) showed sediment loss to be 10 times greater on disturbed land compared to
74
undisturbed, undeveloped hillslopes near La Parguera. Water quality parameters in La Parguera
75
including chlorophyll a and turbidity generally display a decrease from shore-to-shelf indicating
76
land-based sources (Otero, 2009; Hertler et al., 2009), yet, elevated sediment contaminants such
77
as copper do not always fit a similar gradient suggestive of land-based sources but rather, may
78
be attributable to recreational boating activities around popular cays and release of copper from
79
antifouling paint (Hertler et al., 2009). Whatever the source, sediment pollution can reduce light
80
penetration, essential to photosynthetic zooxanthellae inhabiting symbiotic reef corals
81
(Fabricius, 2005), and can also smother and kill corals or divert energy for growth into mucus
82
production and sloughing (Brown and Bythell, 2005). Chemicals, including polycyclic aromatic
AC C
EP
TE D
M AN U
67
3
ACCEPTED MANUSCRIPT
83
hydrocarbons (PAHs), polychlorinataed biphenyls (PCBs), organochlorine pesticides, and
84
butyltins may also adversely affect corals (Pait et al., 2007; 2008).
85
To better understand relationships between coral condition and contaminants, randomly collected samples of marine sediments from La Parguera were analyzed by Pait et al. (2007,
87
2008) to document spatial and chemical patterns that could influence coral condition. A broad
88
suite of chemicals was analyzed, including total and individual PAH and PCB compounds,
89
pesticides, and metals at sites across the La Parguera basin extending eastward to Guánica Bay.
90
Sediment contaminant concentrations were generally higher closer to La Parguera and
91
especially high near Guánica, and lower at sites toward the shelf. The study also demonstrated
92
a negative correlation of coral taxa richness with total PAHs (Pait et al., 2007). To further
93
explore associations between sediment contaminants and reef condition, this survey was
94
designed to assess additional reef fauna at linear reefs along a portion of the sediment
95
contamination gradient in western La Parguera basin. It was hypothesized that presence and
96
condition of reef fauna would decline with greater sediment contamination. Stony corals,
97
gorgonians, sponges, fish and benthic macroinvertebrates were characterized, along with
98
measures of reef rugosity, foraminiferal assemblages and percent mud in the sediments. Reef
99
indicators were tested for responsiveness to two potential proxies of human disturbance: 1) the
100
sediment chemical gradient described by Pait et al. (2007), and 2) increasing distance from the
101
town of La Parguera. The latter variable, distance from human disturbance such as a city or
102
industrial area, has been shown to correlate with coral reef health in the U.S. Virgin Islands
103
(Fisher et al. 2008; Smith et al. 2008). The multi-faunal survey also allowed investigation and
104
description of relationships among reef inhabitants and between reef inhabitants and physical
105
characteristics of the reef.
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86
4
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106
2. Materials and Methods
107
2.1. Survey design
108
Survey sites (24) were selected from benthic habitat maps of the northwestern La Parguera basin (Kendall et al., 2001), targeting an 8m depth at approximately regular
110
intervals along the seaward edge of linear reef habitat. The site locations ran northeast to
111
southwest within a gradient of sediment contamination described by Pait et al., (2007) and
112
ranged from 1- 8km from the town of La Parguera (Fig. 1).
113
2.2. Data collection
SC
The best available coral reef habitat (greatest coral cover by visual estimate) within
M AN U
114
RI PT
109
20m radius of the marker buoy was selected for the survey. A weighted marker buoy was set
116
at each location, to which the first pair of divers attached a 25m tape and swam along the reef
117
contour to establish the transect, count benthic macroinvertebrates (crabs, lobsters, conchs, and
118
sea urchins), identify fish species and estimate their lengths in an area 2m to either side of the
119
tapeline for a total survey area of 100m2 (Menza et al., 2006). Upon completion of the fish
120
and invertebrate survey, the team completed three rugosity measurements using the 6-m line
121
method and collected three small vials of substrate (~10g) at the ends and middle of the
122
transect for analysis of sediment texture (% mud) and foraminiferal assemblages (Hallock et
123
al., 2003). A second pair of divers followed the 25m line with one diver continuously
124
surveying stony corals along a 1m area to one side of the tapeline (total survey area = 25m2)
125
and the other diver surveying gorgonians and sponges in five 1m2 quadrats spaced at regular
126
intervals along the tapeline (total survey area = 5m2) . All stony coral colonies >10cm in any
127
dimension were identified to species level (Humann and Deloach, 2002), colony height and
128
maximum diameter were measured with measuring sticks, and estimates of the percent living
129
tissue on a colony were estimated visually in 10% increments (Fisher, 2007). Colonies that
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115
5
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had no live tissue were included in the survey if it could be determined, by morphology or
131
presence of remaining calices, that the colony was recently dead. Dead colonies with calices
132
were counted as species ‘unknown’ unless the species could be determined from the calices
133
and colony shape. Gorgonians and sponges were classified by morphology rather than species,
134
and colony diameter and height were measured (Santavy et al., 2012).
135
2.3 Indicator calculations
136
2.3.1 Site contaminant ranking and distance to town measurements
SC
137
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130
Survey sites were located near but not superimposed on, National Oceanic and Atmospheric Administration (NOAA) sites where sediment contamination was previously
139
measured (Pait et al. 2007). Indicator kriging procedures applied to the sediment contaminant
140
data provided estimated concentrations at non-sampled areas, so determining actual
141
contaminant concentrations at survey sites could not be done. Instead, since total
142
concentrations of contaminant classes including PAHs, PCBs, and metals were strongly and
143
positively correlated, relative contaminant concentration ranks representative of all chemicals
144
were estimated for the new survey sites.
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To achieve this, survey site coordinates were imported into ArcMap10 (ESRI,
EP
145
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138
Redlands, CA) and superimposed on kriged sediment contaminant layers representing the
147
spatial distribution of total contaminants, non-normalized for silt/clay percentage (courtesy A.
148
Pait, NOAA). Sites were assigned a relative rank of 1 (least contaminated) to 4 (most
149
contaminated) based on their position on kriged layers, with 1 indicating the least
150
contaminated and 4 the most contaminated (Fig. 1, Table 1). Sites within the study range
151
having highest contaminant ranks were clustered near La Parguera and (corresponding to the
152
red zone in Figs. 48 and 49 of Pait et al., 2007) and decreased toward the southwest.
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6
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153
To investigate potential effects on reef fauna from proximity to human activity, distance from each site to a point on the coastline representing the approximate center of La
155
Parguera was measured using the distance tool in ArcMap10. This process generated the
156
variable called distance to town (DTT), an alternative proxy to contaminant rank for the
157
influence of nonpoint runoff.
158
2.3.2. Stony coral surface areas (SAs) and community metrics
RI PT
154
The 3-dimensional (3D) SA of each colony was calculated from dimension
160
measurements using the formula for a hemisphere with varying coefficients depending on
161
morphological complexity (Oliver et al., 2011; Santavy et al. 2012). Stony coral planar (2D)
162
live cover was estimated using the formula for a circle (π r2), adjusted for percent live per
163
colony. For both 3D and planar calculations r = ((diameter/2 ) + height)/2. Averages for 3D
164
colony size (AvCSA), live 3D colony size (AvLvCSA) and percent live tissue were calculated
165
from summed colony values grouped by site or by species and divided by the total number of
166
colonies. Three-dimensional total coral cover (3DTC) and 3D live coral cover (3DLC) were
167
calculated by adding all colony SA values for each site and normalizing as m2 coral per m2 sea
168
floor. Formulas for indicator calculations appear in Oliver et al. (2011, Table 1). Shannon-
169
Weiner diversity index was calculated for stony coral species found at each site according to
170
Clark and Gorley (2006), and taxonomic richness was the total number of species observed at
171
each site. The coefficient of variation (CV) was calculated for stony coral colony size and
172
stony coral live colony size, as a measure of heterogeneity in the population structure.
173
2.3.3. Gorgonian and sponge SAs
174
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159
Three-dimensional SAs for each colony were calculated from measured height and
175
diameter using regression-based formulas developed for morphologies typically found in
176
tropical marine reef environments (Santavy et al., 2013). Gorgonian morphologies included 7
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sea fans (planar and 3D), sea rods (planar, unbranched, branched and bushy) sea whips
178
(branched and bushy) and sea plumes. Sponge morphologies included barrel, vase, globe,
179
mound, ropey, tube, rod, bushy, encrusting and boring. Percentage contribution in terms of
180
number and SA of total gorgonians and sponges was calculated for each morphological type,
181
and total SAs and numbers of each gorgonian and sponge morphology were tallied. Surface
182
areas for living and dead stony corals, gorgonians, and sponges were normalized as m2 per m2
183
sea floor and summed to generate total reef SA.
184
2.3.4. Fish and benthic macroinvertebrates
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177
Total fish abundance, total biomass, average biomass and average length were
186
calculated for each site across all fish species, for fish grouped by dietary preference including
187
piscivores, invertivores, herbivores, zooplanktivores and cleaners (Froese and Pauly, 2005),
188
and for small fish (8000m. The DTT measurement correlated closely with
251
orthogonal distance to shore and both measures yielded similar correlation results with reef
252
indicators. Only DTT was chosen for further analyses. Sites with lower contaminant ranks
253
were further from town as indicated by an inverse correlation between contaminant rank and
254
DTT (r2=0.671, p
S0141-1136(14)00077-4
DOI:
10.1016/j.marenvres.2014.04.005
Reference:
MERE 3882
To appear in:
Marine Environmental Research
Received Date: 4 December 2013 Revised Date:
7 April 2014
Accepted Date: 13 April 2014
Please cite this article as: Oliver, L.M., Fisher, W.S., Dittmar, J., Hallock, P., Campbell, J., Quarles, R.L., Harris, P., LoBue, C, Contrasting responses of coral reef fauna and foraminiferal assemblages to human influence in La Parguera, Puerto Rico, Marine Environmental Research (2014), doi: 10.1016/ j.marenvres.2014.04.005. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
1 2 3 4 5 6 7 8 9 10
Contrasting responses of coral reef fauna and foraminiferal assemblages to human influence in La Parguera, Puerto Rico
11 12 13 14 15 16 17 18 19 20 21 22
2
University of South Florida, 140 7th Ave. S, St. Petersburg, FL 33701
3
U.S. Environmental Protection Agency, Region 2, New York, NY 10007-1866
23
Coral reef biota including stony corals, sponges, gorgonians, fish, benthic macroinvertebrates and
24
foraminifera were surveyed in coastal waters near La Parguera, in southwestern Puerto Rico. The
25
goal was to evaluate sensitivity of coral reef biological indicators to human disturbance. Proxies
26
for human disturbance were measured as distance to town (DTT) and rankings of a low-level
27
sediment contamination gradient analyzed from a previous study. Contaminant rank and DTT
28
showed that percent mud, stony coral taxa richness, reef rugosity, and numbers of invertebrates
29
and sponges were higher at sites closer to human disturbance, but a foraminiferal assemblage
30
index was significantly lower at sites with higher proxies for human disturbance. Fish indicators
31
showed no significant relationships with human activity, but associations between fish community
32
measures and certain measures of stony corals, gorgonians and sponges were found. Contrasting
33
responses between foraminifera and reef organisms may be due to greater exposure and sensitivity
34
of foraminifera to sediment contaminants.
1
Oliver, L.M., 1Fisher, W.S., 1Dittmar, J., 2Hallock, P., 1Campbell, J., 1Quarles, R.L. 1Harris, P. and 3LoBue, C. 1
SC
RI PT
U.S. Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Gulf Ecology Division, 1 Sabine Island Drive, Gulf Breeze, FL 32561-5299
M AN U
Corresponding Author: [email protected] 850 934-2470
Key Words: Coral reef, human disturbance gradient, sediment contaminants, stressors
AC C
EP
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Abstract
1
ACCEPTED MANUSCRIPT
35 36
1. Introduction La Parguera, Puerto Rico hosts a diverse and complex tropical marine ecosystem characterized by mangrove islands, seagrass beds, macroalgal beds, stony corals, gorgonians,
38
sponges and associated fish and invertebrate macrofauna (Pittman et al., 2010; Ballantine et al.,
39
2009). Calcareous structures formed by stony coral reefs provide shoreline protection and
40
support a complex ecology, productive fisheries, and aesthetically-pleasing recreational
41
opportunities for local residents as well as seasonal tourists. Historically, the La Parguera
42
nearshore stony coral reef structure was dominated by Acropora sp. with proportionally more
43
Montastraea sp. at increasing depth (Acevedo et al., 1989), but since the late 1980s, both of
44
these important reef-building species have experienced severe losses (Gardner et al., 2003).
45
Acropora palmata and A. cervicornis have nearly disappeared and the Montastraea species
46
complex (M. faveolata, M. annularis, and M. cavernosa) has also declined from effects of
47
bleaching and disease (Goenaga et al., 1989; Garcia-Sais et al., 2008; Ballantine et al., 2009).
48
Loss of reef resources is well-documented, but less understood are the relative contributions of
49
different stressors to stony coral decline, and how management efforts may optimally work
50
toward decisions that restore the reefs to their historical condition. Understanding which
51
anthropogenic factors have the greatest impact allows prioritization of resources for
52
management action and enforcement, which is essential to ensure delivery of critical reef
53
services (Fore et al., 2009; Bradley et al., 2010).
SC
M AN U
TE D
EP
AC C
54
RI PT
37
While ocean warming, diseases and storms have reduced stony coral condition on a
55
regional scale, anthropogenic changes on land may have compromised Puerto Rico reef habitats
56
through increased runoff of sediments, nutrients and chemical pollutants (Warne et al., 2005;
57
Weber et al., 2006; Richmond et al., 2007). Clearing land for agriculture and municipal
58
development increases the amount of impervious surfaces and reduces the natural barriers to 2
ACCEPTED MANUSCRIPT
watershed runoff, both leading to greater sediment and entrained chemical pollutants entering
60
the marine environment (Rogers, 1990; Fabricius, 2005). Guánica Bay, to the east of La
61
Parguera, has been inundated over the last several decades with sediment from upstream
62
activities including municipal development, road construction and agriculture, particularly
63
coffee farming on the mountain ridges (WMP, 2008). Hydrologic alterations for irrigation and
64
power generation have increased flow to Guánica Bay, where exiting water with entrained
65
sediment generally flows westward in the prevailing current towards La Parguera’s coral reefs
66
(Kaye, 1959).
SC
RI PT
59
Non-point runoff from the area around La Parguera is also a source of sediments,
68
nutrients and contaminants. With a population of approximately 30,000 people, La Parguera is
69
not a large city but is undergoing new development in close proximity to the coast. Analysis of
70
sediment cores collected near La Parguera provided evidence of a human signature as
71
sedimentation rates decreased in a seaward direction, and terrestrial sediment accumulation
72
increased in back-reef sediment compared to fore-reef sediment (Ryan et al., 2008). Ramos-
73
Scharrón (2007) showed sediment loss to be 10 times greater on disturbed land compared to
74
undisturbed, undeveloped hillslopes near La Parguera. Water quality parameters in La Parguera
75
including chlorophyll a and turbidity generally display a decrease from shore-to-shelf indicating
76
land-based sources (Otero, 2009; Hertler et al., 2009), yet, elevated sediment contaminants such
77
as copper do not always fit a similar gradient suggestive of land-based sources but rather, may
78
be attributable to recreational boating activities around popular cays and release of copper from
79
antifouling paint (Hertler et al., 2009). Whatever the source, sediment pollution can reduce light
80
penetration, essential to photosynthetic zooxanthellae inhabiting symbiotic reef corals
81
(Fabricius, 2005), and can also smother and kill corals or divert energy for growth into mucus
82
production and sloughing (Brown and Bythell, 2005). Chemicals, including polycyclic aromatic
AC C
EP
TE D
M AN U
67
3
ACCEPTED MANUSCRIPT
83
hydrocarbons (PAHs), polychlorinataed biphenyls (PCBs), organochlorine pesticides, and
84
butyltins may also adversely affect corals (Pait et al., 2007; 2008).
85
To better understand relationships between coral condition and contaminants, randomly collected samples of marine sediments from La Parguera were analyzed by Pait et al. (2007,
87
2008) to document spatial and chemical patterns that could influence coral condition. A broad
88
suite of chemicals was analyzed, including total and individual PAH and PCB compounds,
89
pesticides, and metals at sites across the La Parguera basin extending eastward to Guánica Bay.
90
Sediment contaminant concentrations were generally higher closer to La Parguera and
91
especially high near Guánica, and lower at sites toward the shelf. The study also demonstrated
92
a negative correlation of coral taxa richness with total PAHs (Pait et al., 2007). To further
93
explore associations between sediment contaminants and reef condition, this survey was
94
designed to assess additional reef fauna at linear reefs along a portion of the sediment
95
contamination gradient in western La Parguera basin. It was hypothesized that presence and
96
condition of reef fauna would decline with greater sediment contamination. Stony corals,
97
gorgonians, sponges, fish and benthic macroinvertebrates were characterized, along with
98
measures of reef rugosity, foraminiferal assemblages and percent mud in the sediments. Reef
99
indicators were tested for responsiveness to two potential proxies of human disturbance: 1) the
100
sediment chemical gradient described by Pait et al. (2007), and 2) increasing distance from the
101
town of La Parguera. The latter variable, distance from human disturbance such as a city or
102
industrial area, has been shown to correlate with coral reef health in the U.S. Virgin Islands
103
(Fisher et al. 2008; Smith et al. 2008). The multi-faunal survey also allowed investigation and
104
description of relationships among reef inhabitants and between reef inhabitants and physical
105
characteristics of the reef.
AC C
EP
TE D
M AN U
SC
RI PT
86
4
ACCEPTED MANUSCRIPT
106
2. Materials and Methods
107
2.1. Survey design
108
Survey sites (24) were selected from benthic habitat maps of the northwestern La Parguera basin (Kendall et al., 2001), targeting an 8m depth at approximately regular
110
intervals along the seaward edge of linear reef habitat. The site locations ran northeast to
111
southwest within a gradient of sediment contamination described by Pait et al., (2007) and
112
ranged from 1- 8km from the town of La Parguera (Fig. 1).
113
2.2. Data collection
SC
The best available coral reef habitat (greatest coral cover by visual estimate) within
M AN U
114
RI PT
109
20m radius of the marker buoy was selected for the survey. A weighted marker buoy was set
116
at each location, to which the first pair of divers attached a 25m tape and swam along the reef
117
contour to establish the transect, count benthic macroinvertebrates (crabs, lobsters, conchs, and
118
sea urchins), identify fish species and estimate their lengths in an area 2m to either side of the
119
tapeline for a total survey area of 100m2 (Menza et al., 2006). Upon completion of the fish
120
and invertebrate survey, the team completed three rugosity measurements using the 6-m line
121
method and collected three small vials of substrate (~10g) at the ends and middle of the
122
transect for analysis of sediment texture (% mud) and foraminiferal assemblages (Hallock et
123
al., 2003). A second pair of divers followed the 25m line with one diver continuously
124
surveying stony corals along a 1m area to one side of the tapeline (total survey area = 25m2)
125
and the other diver surveying gorgonians and sponges in five 1m2 quadrats spaced at regular
126
intervals along the tapeline (total survey area = 5m2) . All stony coral colonies >10cm in any
127
dimension were identified to species level (Humann and Deloach, 2002), colony height and
128
maximum diameter were measured with measuring sticks, and estimates of the percent living
129
tissue on a colony were estimated visually in 10% increments (Fisher, 2007). Colonies that
AC C
EP
TE D
115
5
ACCEPTED MANUSCRIPT
had no live tissue were included in the survey if it could be determined, by morphology or
131
presence of remaining calices, that the colony was recently dead. Dead colonies with calices
132
were counted as species ‘unknown’ unless the species could be determined from the calices
133
and colony shape. Gorgonians and sponges were classified by morphology rather than species,
134
and colony diameter and height were measured (Santavy et al., 2012).
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2.3 Indicator calculations
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2.3.1 Site contaminant ranking and distance to town measurements
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Survey sites were located near but not superimposed on, National Oceanic and Atmospheric Administration (NOAA) sites where sediment contamination was previously
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measured (Pait et al. 2007). Indicator kriging procedures applied to the sediment contaminant
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data provided estimated concentrations at non-sampled areas, so determining actual
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contaminant concentrations at survey sites could not be done. Instead, since total
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concentrations of contaminant classes including PAHs, PCBs, and metals were strongly and
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positively correlated, relative contaminant concentration ranks representative of all chemicals
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were estimated for the new survey sites.
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To achieve this, survey site coordinates were imported into ArcMap10 (ESRI,
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Redlands, CA) and superimposed on kriged sediment contaminant layers representing the
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spatial distribution of total contaminants, non-normalized for silt/clay percentage (courtesy A.
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Pait, NOAA). Sites were assigned a relative rank of 1 (least contaminated) to 4 (most
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contaminated) based on their position on kriged layers, with 1 indicating the least
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contaminated and 4 the most contaminated (Fig. 1, Table 1). Sites within the study range
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having highest contaminant ranks were clustered near La Parguera and (corresponding to the
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red zone in Figs. 48 and 49 of Pait et al., 2007) and decreased toward the southwest.
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To investigate potential effects on reef fauna from proximity to human activity, distance from each site to a point on the coastline representing the approximate center of La
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Parguera was measured using the distance tool in ArcMap10. This process generated the
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variable called distance to town (DTT), an alternative proxy to contaminant rank for the
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influence of nonpoint runoff.
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2.3.2. Stony coral surface areas (SAs) and community metrics
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The 3-dimensional (3D) SA of each colony was calculated from dimension
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measurements using the formula for a hemisphere with varying coefficients depending on
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morphological complexity (Oliver et al., 2011; Santavy et al. 2012). Stony coral planar (2D)
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live cover was estimated using the formula for a circle (π r2), adjusted for percent live per
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colony. For both 3D and planar calculations r = ((diameter/2 ) + height)/2. Averages for 3D
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colony size (AvCSA), live 3D colony size (AvLvCSA) and percent live tissue were calculated
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from summed colony values grouped by site or by species and divided by the total number of
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colonies. Three-dimensional total coral cover (3DTC) and 3D live coral cover (3DLC) were
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calculated by adding all colony SA values for each site and normalizing as m2 coral per m2 sea
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floor. Formulas for indicator calculations appear in Oliver et al. (2011, Table 1). Shannon-
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Weiner diversity index was calculated for stony coral species found at each site according to
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Clark and Gorley (2006), and taxonomic richness was the total number of species observed at
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each site. The coefficient of variation (CV) was calculated for stony coral colony size and
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stony coral live colony size, as a measure of heterogeneity in the population structure.
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2.3.3. Gorgonian and sponge SAs
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Three-dimensional SAs for each colony were calculated from measured height and
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diameter using regression-based formulas developed for morphologies typically found in
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tropical marine reef environments (Santavy et al., 2013). Gorgonian morphologies included 7
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sea fans (planar and 3D), sea rods (planar, unbranched, branched and bushy) sea whips
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(branched and bushy) and sea plumes. Sponge morphologies included barrel, vase, globe,
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mound, ropey, tube, rod, bushy, encrusting and boring. Percentage contribution in terms of
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number and SA of total gorgonians and sponges was calculated for each morphological type,
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and total SAs and numbers of each gorgonian and sponge morphology were tallied. Surface
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areas for living and dead stony corals, gorgonians, and sponges were normalized as m2 per m2
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sea floor and summed to generate total reef SA.
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2.3.4. Fish and benthic macroinvertebrates
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Total fish abundance, total biomass, average biomass and average length were
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calculated for each site across all fish species, for fish grouped by dietary preference including
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piscivores, invertivores, herbivores, zooplanktivores and cleaners (Froese and Pauly, 2005),
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and for small fish (8000m. The DTT measurement correlated closely with
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orthogonal distance to shore and both measures yielded similar correlation results with reef
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indicators. Only DTT was chosen for further analyses. Sites with lower contaminant ranks
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were further from town as indicated by an inverse correlation between contaminant rank and
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DTT (r2=0.671, p
