CW Invert and 3D Thesis4 KLM

Role of surface characteristics and mobile
invertebrates on settlement choices and
post- settlement survivorship of three
scleractinian coral species
Christopher Michael White
Student #: 10406689
July 30th
, 2014
University of Amsterdam 
Faculty of Science: Master Biological Sciences
Track: Limnology and Oceanography
Supervisor: Dr. Kristen L. Marhaver
Examiner: Dr. Mark J.A. Vermeij

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Table ofContents
THESIS ABSTRACT: 3
3D printing and settlement preference of two brooding scleractinian corals, a novel
approach to rethinking artificial reef building
ABSTRACT: 4
INTRODUCTION: 4
METHODS: 7
LARVAE COLLECTION 7
SETTLEMENT TILES 8
CORAL LARVAE COLOR CHOICE EXPERIMENT I 9
CORAL LARVAE COMPLEXITY CHOICE EXPERIMENT II 10
DATA ANALYSIS 10
RESULTS: 11
CORAL LARVAE COLOR CHOICE EXPERIMENT I 11
COMPLEXITY CHOICE EXPERIMENT II 13
DISCUSSION: 15
COLOR PREFRENCE 15
COMPLEXITY PREFERENCE 17
IMPLICATIONS IN ARTIFICIAL REEF RESTORATION 18
REFERENCES: 19
The ability of mobile reef invertebrates to influence coral settler survivorship
ABSTRACT: 22
INTRODUCTION: 22
METHODS: 25
RESEARCH LOCATION 25
STUDY SPECIES 26
EXPERIMENTAL DESIGN 1-6 27-32
DATA ANALYSIS 35
RESULTS: 36
EXPERIMENTS 1,2:M. FAVEOLATA RESPONSE TO CONDITIONED SEAWATER AND SURFACES 36-38
EXPERIMENT 3:M. FAVEOLATA SURVIVORSHIP WITH VARYING INVERTEBRATES 39
EXPERIMENT 4:F. FRAGUM SURVIVORSHIP WITH VARYING INVERTEBRATES 41
EXPERIMENT 5:A. HUMILIS SURVIVORSHIP WITH VARYING INVERTEBRATES 42
EXPERIMENT 6:FIELD STUDY ON INVERT. REEF TRAFFIC & F. FRAGUM SETTLER SURVIVORSHIP 44
DISCUSSION: 47
SETTLEMENT OF CORAL LARVAE: 47
INVERTEBRATE INTRODUCTIONS: 49
DECAPODS AND POLYCHAETES 49
GASTROPODS 51
ECHINODERMS 52
FIELD EXPERIMENT ON REEF: 53
CONCLUSION: 56
REFERENCE: 57
ACKNOLOGEMENTS 62
APPENDIX PILOT STUDIES 7 & 8 62

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Abstract:
Coral reefs, while occupying 1% of the oceans, provide habitat for a quarter of all
sea life. Scleractinian corals in particular build the foundation of the majority of structural
habitats found on reefs and are often referred to as ecosystem engineers (Williams et al.
2009). Their life histories, overall health, as well as their responses to biotic as well as
abiotic factors are therefore fundamentally important in our overall understanding of
coral reef systems.
Recently, coral reef health and recovery has been found to be particularly
dependent on coral larvae availability, settlement ecology, and post settlement
survivorship (Williams et al. 2009). Investigating the early life stages of various
scleractinian coral species, especially larval settlement preferences and post settlement
biological interactions, may therefore contribute to the foundation of our knowledge
regarding these systems. This report therefore focuses on two principle areas of research.
One, using innovative 3D technology to print various surface types in numerous colors,
surface and color settlement preferences of two scleractinian coral species, Favia fragum
and Agaricia humilis were investigated. The second investigation involved mapping the
interactions of various coral reef mesograzers with settlers of the coral species Favia
fragum, Agaricia humilis, and Montastraea faveolata, in an attempt to deduce the
invertebrate ecological influence on early life stages of those corals.

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3D printing and settlement preference
of two brooding scleractinian corals, a
novel approach to rethinking artificial
reef building
Abstract:
Corals are subject to various pressures throughout their life histories that can
contribute to mortality, particularly during early life stages. Newly released coral larvae
handle these pressures by settling in favorable locations, taking into account factors such
as light, location, sedimentation, depth, and biotic competition. This study was conducted
in the southern Caribbean, on the leeward side of Curacao. Using 3D printing technology,
the settlement surface preferences for both color and surface complexity were determined
for larvae of two scleractinian coral species. Two brooding coral species were tested,
Favia fragum and Agaricia humilis. Both exhibited settlement preferences for white tiles
when presented color choices, however A. humilis showed a broader range of surface
preferences settling on both red and black tiles. Surface complexity played less of a role
in larvae settlement preferences for both species, while it is thought that larvae from both
species were more interested in settling relative to light exposure and not complexity
alone. These findings show that larvae from these two species choose surfaces that most
closely resemble the natural habitat in which they are prone to survive. A novel approach
for artificial reef building may be feasible by mimicking natural conditions for
scleractinian corals with the advent of 3D printing technology in future projects.

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Introduction:
Coral larvae settlement cues and settlement surface preferences are the subject of
increasing research attention. Factors such as substrate orientation, chemical cues,
progeny distance from adults, and light have all been shown to influence larvae
settlement preferences and survivorship (Marhaver et al. 2013, Mason et al. 2011,
Harrington et al. 2004, Vermeij and Sandin 2004, Carlton and Sammarco 1987). In adult
corals, light is known to affect tentacle expansion and contraction, the regulation of
circadian clocks, and reproductive timing (Mason et al. 2012). Most recently,
photoreceptors in coral species were found to be a factor in coral larvae settlement
preferences. Mason et al. (2011) found using larvae of Porites astreoides and Acropora
palmata that chemical cues may be primarily responsible for settlement of larvae, but that
color also acts as a settlement cue. Notably, the color preference of Porites astreoides and
Acropora palmata was absent when the same experiment was conducted in the dark
(Mason et al. 2011). Mason et al. (2012) recently found genes in Acropora palmata that
code for acropsins, amino acid sequences similar to opsin proteins, which are photo
pigments known to occur in animals. These specific acropsins were found to align most
closely with rhodopsins of Homo sapiens and the veined squid Loligo forbesi. The ability
of juvenile corals to detect color could enable them to distinguish between different
species of crustose coralline algae (CCA), facilitating survival of coral settlers (Mason et
al. 2011).
Our knowledge of larval settlement surface preference and post-settlement
survivorship is important in understanding coral recruitment rates and patterns in general.
Additionally, as coastal development accelerates in the form of road systems, housing,

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agriculture, and industry, disturbances such as sedimentation events, eutrophication
through waste effluent, and direct habitat destruction are likely to become more regular.
Disturbances like these may lead to changes in larval settlement patterns and overall
success. Due to reductions in overall reef system health and disproportionately large
disturbances on shallow reef systems, and given that shallow reef systems are
increasingly of interest for local tourism industries, understanding settlement preferences
of shallow water species may yield important insights in the functioning of reef
ecosystems.
Favia fragum is a scleractinian hermaphroditic coral that is limited in habitat
range, encountered mostly in the shallows of 3 m or less, attached to a variety of hard
surfaces and commonly found in the Caribbean (Goodbody and Putron 2009, Szmant-
Froelich et al. 1985). These shallow water habitats are often dominated by rubble and
prone to higher rates of disturbance from wave action and storms (Carlon 2002, Szmant-
Froelich et al. 1985).
Agaricia humilis, also a scleractinian coral commonly found in the Caribbean, can
be found in slightly deeper water, but is still limited for the most part to a depth of less
than 10 m, primarily occurring on shallow reefs and reef flats (Van Moorsel 1983).
Shallower depths of 10-20 m are known to have an increased level of disturbance in
comparison to similar landscapes at 30-40 m (Bak and Luckhurst 1980). This may have
contributed to the selective pressure for these two brooding coral species to planulate
throughout the year (Szmant-Froelich et al. 1985). Due to the fact that these coral species
recruit to an area with high levels of disturbance, it makes it that much more important
for larvae to settle on surfaces protected from disturbances.

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Here, larvae from two species of scleractinian corals, F. fragum and A. humilis,
were given the opportunity to settle on artificial 3D-printed plastic surfaces of various
textures and colors. The aim was to test if larvae exhibited a preference for a specific
color and to determine which surface texture was preferred. 3D printing technology is
quickly being assimilated to support the activities and efforts of our daily lives. As costs
come down for printing of plastic parts, biological tissues, and even entire buildings,
technological developments are being realized more quickly. Therefore, in addition to
obtaining a better understanding of these two species’ settlement preferences, we show
how 3D printing technology may act as another tool in the near future for promoting
coral recruitment to artificial reefs within the shallow coral reef ecosystem.
Methods:
Larvae collection
38 colonies of Favia fragum and 23 colonies of Agaricia humilis were collected
from shallow reefs in Curacao at the Water Factory (12°6'37"N, 68°57'7"W) and
Piscaderabaai (12°7'20"N, 68°57'53"W) dive sites. Both collection sites are located on
the leeward, southwest coast of Curacao. Goodbody and Putron (2009) found over a four-
year period that F. fragum predictably begins releasing larvae three to four days after the
new moons between July and August, continuing for up to 19 days in total. Recorded
peaks in F. fragum planulation in Bermuda (Goodbody and Putron 2009) are correlated
with peaks in larval release in Puerto Rico and the US Virgin Islands (Carlon 2002,
Szmant-Froelich et al. 1985). In all three of these studies, larval release peaked six to
twelve days after the new moon. In this experimental time period for the current study,
peaks in F. fragum larval release in February and March of 2014 occurred on the 12th and

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10th day following the new moon, respectively. Parent F. fragum colonies were collected
on February 5th 2014. A. humilis colonies were collected on March 5th 2014, with a larvae
release peak recorded the following day, five days after the new moon.
All corals were kept in the flow-through aquarium system at CARMABI. Each
coral was placed in an individual plastic beaker with a tube providing a continual flow of
fresh seawater. Water overflow ran onto a submerged 200 m filter (nylon mesh) held in
place using 6.35 cm diameter PVC piping. As larvae were released and floated to the
water surface, water flowed onto the submerged mesh for collection. Aquariums with
adult colonies were surrounded with shade cloth overnight to block out artificial light and
promote coral planulation. At sunrise, larvae were pipetted out of the filters into plastic
polystyrene containers filled with 0.45 m-filtered seawater (0.45 m FSW). Larvae
were pooled over multiple days of collection to obtain enough individuals for
experiments with sufficiently high replication. For each experiment, a mixed cohort of
one- and two-day-old larvae was used as daily larvae harvest rates varied. Larvae were
added to experimental treatments within two days of being collected.
Settlement tiles
Tiles were printed in white, black, and red plastic (Acrylonitrile butadiene
styrene; ABS) using an “UP!-Mini 3D printer” (Robotshop inc., Swanton/USA). Tiles
measured 4.15 cm in length by 4.15 cm in width with a thickness of 5 mm (Figure 1).
Features on the tiles added an additional maximum thickness of 1 cm. Tiles had a flat
surface faced upwards with four different surfaces on the underside: cones, bumps, flat,
and open cylinders. Tiles were designed using Blender software (Version 2.70, Blender
foundation). Four larger cones were located in the corners to act as support structures to

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suspend the side with the complex printed
surfaces face down in the water column
(Figure 1).
Tiles were then secured, with textured
surfaces up, to 15 cm2 sections of white
plastic ceiling panels i.e., “egg crating”
(Plaskolite, Columbus/USA)
with plastic tie wraps. These panels were
then secured to the seabed in Piscaderabaai at a depth of five meters for five weeks. This
allowed for the development of biofilms and a small amount of colonization by CCA.
After five weeks, tiles were removed from the reef and lightly scrubbed with a test tube
cleaning brush to remove any large detritus and sediment.
Color choice (Experiment I)
Six clear plastic polystyrene containers with lids were filled with 180 ml of 200
m-filtered seawater (200 m FSW). 60 F. fragum coral larvae were added to each
container along with three tiles, one of each color, arranged haphazardly within each bin.
Larvae were released in the two days prior to beginning the experiment and pooled to
create an experimental cohort. The water in each container fully covered the 3D printed
tiles, which were negatively buoyant following light fouling by calcifying algae. Bins
were placed in the laboratory at CARMABI where temperature was maintained at 29˚C
with an alternating 12-hour light:dark regime. The light source consisted of overhead
fluorescent lights and diffused natural light from a strip of high windows. Tiles were
scored for settlers using a blue light and barrier filter system every 48 hr after initiation
Figure 1: Tiles design in Blender
(View-Bottom face up)

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until day 8. The blue lights used include a dive light with separate fluorescence excitation
filter, a BlueStar flashlight, or a Dual Fluorescent Protein Flashlight (all manufactured by
NightSea, Bedford/USA). Settlement was defined as the complete metamorphosis of
larvae into an oral-aborally flattened primary polyp with observable feeding tentacles and
secretion of a basal plate (Mason et al. 2011). Of the three colored tiles offered, the tile
color as well as specific location of each settler was scored as having settled on the top
flat surface, on the sides of tiles, or on the underside of the tile in one of the four sections
with different textures. The experiment was continued for eight days. Over the course of
the experimental period, the maximum number of settled larvae on each tile was
recorded. As larvae can only go through metamorphism once, are considered independent
from each other, and as some mortality occurred towards the end of the experimental
time period, this methodology was preferred as it gave each larva an equal choice
opportunity.
The same experiment was repeated using the brooding species A. humilis
following the F. fragum experiment. Following obtaining results for F. fragum, juvenile
F. fragum settlers were scraped off the tiles using a razor blade and tiles were placed in
an aquarium where they were allowed to foul for an additional two weeks prior to the A.
humilis choice experiment. A. humilis colonies, collected on 5 March 2014, began
planulation immediately. Larvae collection methodology followed that for F. fragum.
Using the same tiles, the experiment was repeated with A. humilis using the same
methodology as for F. fragum.

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Complexity choice (Experiment II)
Nine 235 ml clear plastic polystyrene cups with lids were filled with 60 ml 200
m FSW. A mixed cohort of larvae one to two days old was used. 30 F. fragum larvae
were added to each cup along with one white plastic tile, manufactured in the same
fashion as the other 3D settlement tiles. Tiles were scored for settlers using one of the
same blue light systems mentioned above every 48 hr for 6 days. The location of settlers
was recorded as having settled on the top flat surface, on the sides of tiles, or on the four
different textured areas on the underside of tiles. The methodology of taking the
maximum number of settlers over the experimental time period was maintained and the
experiment was repeated using A. humilis after tiles went through the same conditioning
process as the color choice experiment, following obtaining results for F. fragum.
Data analysis
After the eight day time period, the maximum number of settlers per tile was
recorded for each color and or complexity type. Aggregative coral settlement has been
observed to occur in P. astreoides and A. palmata, leading some researchers to consider
dishes as the smallest independent unit of measurement (Mason et al. 2011). However,
Gaines and Roughgarden (1985) described the settlement of barnacle larvae as a process
where settlement to a given area was proportional to the available space of that area. At
low densities, larvae settlement was determined to be independent of other larvae
settlement (Gaines and Roughgarden 1985). Thus, at low densities in this experiment
where we had a maximum density of one larva per 2 ml seawater, we assume settlement
of each larva to be independent.
For complexity and orientation, coral settlement location fell into four categories;

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flat tops of tiles, sides of tiles, flat bottoms of tiles, and complex bottom areas of tiles.
Due to the varying size of each surface type available to larvae, total surface area of tiles
was calculated and sub-divided based on relative percentage of each respective area.
Results:
Color choice experiment (Experiment I)
In the color preference experiment, if the overall sum of settlers, aggregated
across all replicates is compared to the total number of coral larvae introduced (300),
only 16.5 percent of the Favia fragum introduced to settlement bins settled within the
eight-day allotted experimental time period. Of the 51 larvae that settled, settlement onto
white tiles was significantly higher than settlement on the other two colors when average
settlement across replicates were compared to expected settlement of a random
distribution across the three available tiles (Chi-square = 8.8748, DF = 2, P = 0.011827).
For A. humilis, a similar result was observed. The majority of settlement occurred on
white tiles (Chi-square = 7.0941, DF = 2, P = 0.028809). However, A. humilis exhibited a
more generalist behavior; a larger proportion of Agaricia humilis settlers were found on
red and black tiles as compared to F. fragum (Table 1).

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Figure 2: A. A. humilis and B. F. fragum 3D tiles color choice settlement across
replicates. Key: White- settled on white tile, black- settled on black tiles, dark grey-
settled on red tiles, light grey- not settled. C. Average proportion of A. humilis (white)
and F. fragum (black) that settled each color tile. Standard error shown.
Table 1: Color settlement preference of two brooding scleractinian coral species
Agaricia humilis
Treatment White Black Red
Average 0.294444444 0.072222222 0.113888889
Expected 0.33 0.33 0.33
Standard deviation 0.144401703 0.0704483 0.0464479
Standard error 0.058951748 0.028760398 0.018962276
Chi-square = 7.0941, DF = 2, P = 0.028809.
Favia fragum
Treatment White Black Red
Average 0.119444444 0 0.022222222
Expected 0.33 0.33 0.33
Standard deviation 0.093936543 0 0.031031645
Standard error 0.038349433 0 0.012668616
Chi-square = 8.8748, DF = 2, P = 0.011827.
0
10
20
30
40
50
60
1 2 3 4 5 6
#ofsettlers
Replicate
A.
0
10
20
30
40
50
60
1 2 3 4 5 6
#ofsettlers
Replicate
B.
0
0.1
0.2
0.3
0.4
White Black Red
Proportionoflarvaethat
settled
Color tiles
C.

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Complexity choice experiment (Experiment II)
Larval settlement choice for various surface complexity types followed similar
trends to what would be expected under a random distribution of the available space.
Although settlement was not significantly different than a random distribution,
differences between species are still visible. F. fragum preferred the light-exposed flat
surfaces of tiles to all other surfaces and showed minimal settlement on the flat bottom
(shaded) surfaces. A humilis preferred the cryptic shaded area over either of the flat light
exposed or flat shaded surfaces in relation to F. fragum (Figure 2).
Table 2: Color settlement preference of two brooding scleractinian coral species
Agaricia humilis
Treatment Flat top Side Complex bottom Flat bottom
Average 0.159259259 0.1 0.207407407 0.02962963
Expected 0.4 0.2 0.3 0.1
Standard deviation 0.105116044 0.070710678 0.122222222 0.035136418
Standard error 0.035038681 0.023570226 0.040740741 0.011712139
Chi-square = 0.5426, DF = 3, P = 0.909427.
Favia fragum
Treatment Flat top Side Complex bottom Flat bottom
Average 0.27037037 0.122222222 0.140740741 0.003703704
Expected 0.4 0.2 0.3 0.1
Standard deviation 0.196104029 0.133333333 0.12886015 0.011111111
Standard error 0.06536801 0.044444444 0.042953383 0.003703704
Chi-square = 2.0523, DF = 3, P = 0.561621.

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Figure 3: A. humilis (black) and F. fragum (grey) 3D larvae settlement choice compared
to expected (white) normal distribution based off of available area of each complexity
type. A. humilis- Chi-square = 0.5426, DF = 3, P = 0.909427. F. fragum- Chi-square =
2.0523, DF = 3, P= 0.561621.
Discussion:
Color preference
The narrow ovulation of Favia fragum occurs within two to three days after the
new moon (Szmant-Froelich et al. 1985). This ability to time reproduction precisely using
available light yields insight into F. fragum’s capability as adult colonies to measure light
(Szmant-Froelich et al. 1985). Goodbody-Gringley (2010) additionally found that larvae
of F. fragum released right before sunrise exhibited a higher settlement rate than larvae
that were released just after sunset. This led Goodbody-Gringley to hypothesize that
newly released larvae with access to cues available under light conditions would be more
prone to locate suitable habitat for settlement quickly. This allowed them to conclude that
light plays a significant role in settlement behavior and success of F. fragum larvae
(Goodbody-Gringley 2010). Corals’ success in measuring light is not limited to F.
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
Flat top Side Complex bottom Flat bottom

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fragum. Miller and Mundy (2003) found similar results for broadcast spawning of
Platygyra daedalea with peaks in settlement corresponding to morning daylight hours.
F. fragum and A. humilis larvae had a distinct preference for white settlement
surfaces. However, the larvae of A. humilis exhibited a more generalist behavior, settling
on red and black tiles as well. Researchers have studied the connection between color
choice and settler survivorship in the past, with some attributing color preference for
settling on favorable surfaces such as CCA. Mason et al. (2011) found that Porites
astreoides and Acropora palmata, two species that often prefer to settle on CCA,
exhibited higher settlement on red surfaces than green or white surfaces. Vermeij and
Sandin (2004) found that higher survival of Siderastrea radians settlers was correlated
with proximity to CCA. Investigations of larval settlement and settler survival in the
Pacific coral species Acropora tenuis and A. millepora revealed that larvae preferred to
settle onto CCA, especially Titanoderma prototypum, and that this was correlated with
increased survivorship when compared to coral settlers on other species of CCA
(Harrington et al. 2004).
However, our results with two shallow water species F. fragum and A. humilis
show a significant preference for white tiles when given the choice between white, red, or
black (Figure 1). This may be explained by the typical habitat of F. fragum, which often
occurs in shallow reef flat habitats (Goodbody-Gringley 2010, Goodbody-Gringley and
Putron 2009, Reutter and Riggs 1985). These habitats are often composed of sand,
rubble, and solid limestone substrate, with minimal CCA coverage. Thus settlement
habitats of F. fragum are oftentimes white and not the pink-red of CCA that deeper reef
environments often harbor in greater amounts. As F. fragum has evolved to thrive in
shallow water environments, their larvae seem conditioned to use color as a tool for

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seeking this habitat. Additional signaling cues may be at work when in-situ conditions are
present. When given the opportunity to settle on rubble from a similar depth habitat than
rubble from deeper origins, (Carlon 2002) found F. fragum preferred rubble from shallow
origins. Studies such as Carlon’s in conjunction with our color preference results show
how larvae play an active role in seeking ideal habitat, relying on a host of factors to
make settlement decisions.
As with F. fragum, A. humilis larvae also showed a preference for white tiles
when given the choice between white, red, and black. However, A. humilis exhibited a
broader settlement preference, settling on both black and red tiles. In previous studies, A.
humilis were shown to metamorphose at a higher rate when CCA was present, with
settlement almost entirely on the CCA surface when available (Morse et al. 1988). This
species has a greater depth range than F. fragum, a factor that could explain the broader
variety of surface colors to which A. humilis settled in our experiments. If we take into
consideration the previous color preference work of Mason et al. (2011) on Porites
astreoides and Acropora palmata, we observe how species show species-specific color
preferences relative to the characteristics of the habitats in which that species prefers to
settle and is most likely to survive.
Complexity preference
F. fragum settled more on flat, light exposed surfaces, than sides or undersides of
tiles (Table 2). Goodbody-Gringley (2010) also found that F. fragum larvae did not settle
on underside of settlement tiles when given the chance. Conversely, A. humilis showed a
high affinity for complex undersides of tiles (Table 2). In previous research, Morse et al.

18
(1988) also found differences in settlement preferences for exposed and cryptic habitats
for two Agaricia species.
Babcock and Mundy (1996) found that larvae of Platygyra sinensis, a shallow-
reef scleractinian coral species, as well as Oxypora lacera, a deep-reef coral species with
preference for shaded habitats, both exhibited settlement responses that depended on light
regimes. Both species settled underneath tiles when exposed to high light, and both
species settled on the tops of tiles when exposed to low light. As F. fragum and A.
humilis showed preferences for either tops or bottoms of tiles and no distinction between
the species noted for settlement on the sides of tiles, light exposure is likely the dominant
factor for where larvae chose to settle vs. complexity alone in this study (Table 2). Future
efforts should focus on designing 3D tiles that take light into consideration when
providing clear complexity choice variables to coral larvae.
Potential for application in artificial reef restoration
It is interesting to note from this experiment the differences between two species’
preferences for color and possibly light intensity. Additional work shows our results do
not stand alone, with numerous coral species exhibiting preferences in the planular stage
for specific color regimes. Considering these results and with the dramatic progress in 3D
printing technology, the implications for artificial reef restoration are numerous. Spieler
et al. (2001) highlighted two goals for artificial reef restoration: 1) to define the surfaces
to be used to accomplish the set out goals, and 2) to identify the interactions of reef biota
with this surface given its texture and orientation, and given the current state of the
environment. They additionally stated that the choice of artificial surface should take into
account texture, color, chemistry, profile, shelter, shading, size, configuration, stability,

19
settlement attractants, economy, and availability (Spieler et al. 2001). Effective design
therefore depends on local ecology. Carlton and Sammarco (1987) found corals in the
Great Barrier Reef generally preferred vertically oriented substrates, which could differ
from corals in the Caribbean or elsewhere in the world. Thus, if one application is found
to work in a given area, it may not necessarily be as successful when implemented
somewhere else.
However, in order to provide different coral species, which occur at different
depth ranges, with their preferred surface color, irradiance level, and surface settlement
cues, a successful artificial reef substrate could involve a multi-layered structure,
designed to attract larvae of different coral species over different depth ranges. Materials
used in 3D printing to date include plastics, biotic tissues, minerals, metals, and even
concrete. Thus, 3D printing of surface coatings, pier wrappings, or pilings themselves
could include differently-colored sections at different depths, along with variable surface
textures to promote colonization of the entire piling by different species. This concept
could also perhaps be applied to exposed and sheltered sides of reef breaks. As our
knowledge of coral ecology continues to expand, a single solution approach becomes
increasingly difficult to support, and only in our continual creativity, do we poses the
capacity to enact positive, well-thought-out artificial reef restoration projects.
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Bak, R. P. M., and B. E. Luckhurst. 1980. Constancy and change in coral reef habitats

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Carleton, J. H., and P. W. Sammarco. 1987. Effects of substratum irregularity on success
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Carlon, D. B. 2002. Production and supply of larvae as determinants of zonation in a
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on red surfaces. Coral Reefs 30:667-676.

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Mason, B., M. Schmale, P. Gibbs, M. W. Miller, Q. Wang, K. Levay, V. Shestopalov,
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reef-building coral. PLoS ONE 7:e50371.
Miller, K., and C. Mundy. 2003. Rapid settlement in broadcast spawning corals:
implications for larval dispersal. Coral Reefs 22:99–106.
Van Moorsel, G. W. N. M. 1983. Reproductive strategies in two closely related stony
corals (Agaricia, Scleractinia). Marine Ecology 13:273-283.
Morse, D. E., N. Hooker, A. N. C. Morse, and R. A. Jensen. 1988. Control of larval
metamorphosis and recruitment in sympatric agariciid corals. Journal of
Experimental Biology and Ecology 116:193-217.
Sammarco, P. W. 1985. The Great Barrier Reef vs. the Caribbean: comparisons of
grazers, coral recruitment patterns and reef recovery. Proceedings of the Fifth
International Coral Reef Congress 4:391-398.
Spieler, R. E., D. S. Gilliam, and R. L. Sherman. 2001. Artificial substrate and coral reef
restoration: what do we need to know to know what we need. Bulletin of Marine
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fragum (Esper): lunar patterns of gametogenesis, embryogenesis and planulation
in Puerto Rico. Bulletin of Marine Science 37:880–892.
Vermeij, M. J. A., and S. A. Sandin. 2004. Density-dependent settlement and mortality
structure the earliest life phases of a coral population. Ecology 89:1994-2004.
Williams, R. R., S. N. Arnold, N. D. Fogarty, R. S. Steneck, M. J. A. Vermeij, and V. J.
Paul. 2009. New perspectives on ecological mechanisms affecting coral
recruitment on reefs. Smithsonian Contributions to Marine Sciences 38:437-452.

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The ability of mobile reef invertebrates
to influence coral settler survivorship
Abstract:
Coral settlers experience substantial mortality in the time between settlement and
adulthood. Although studies have shown that this high mortality rate may be due to
various abiotic factors and biotic competition with algae, less is known about interactions
with mesograzer invertebrates. The present study took place on the leeward side of
Curacao at the CARMABI marine research station in the 2013-2014 winter season. In
this study, various mesograzers including echinoderms, decapods, gastropods, and
predatory polychaetes were introduced to newly-settled polyps of three scleractinian coral
species. Coral survival and invertebrate behaviors were then observed. Decapods had an
overall negative influence on coral survivorship and size of individual coral settlers and
crabs may have been a contributing factor. A size effect was also observed for predatory
polychaetes, while other invertebrate coral interactions, influenced coral survivorship in
positive, negative, and neutral ways depending on the invertebrate and coral species in
question. In addition, a field experiment was conducted on a shallow reef near
CARMABI, revealing that reef traffic is highly structured in space, highly localized, and
increases at night. Traffic was comprised primarily of various decapods. Areas of
increased traffic were associated with higher levels of coral settler mortality. Both lab and
field experiments provide evidence that mobile reef invertebrates play a role in coral
ecology by influencing early life stage coral settler survivorship.

23
Introduction:
Coral larvae face a gauntlet of challenges before adulthood, including finding a
suitable place for settlement. When finally attached, coral settlers become particularly
vulnerable to abiotic threats such as sedimentation, wave action, storms, and
eutrophication, as well as biotic threats. Algae are a widely-recognized biotic source of
mortality for juvenile corals as they can hinder coral recruitment by preemptively taking
up space, reducing local water flow, releasing secondary metabolites, altering microbial
communities, and blocking sunlight from corals (Williams et al. 2009). While turf algae,
benthic cyanobacteria, and many macroalgae have a known ability to negatively affect
coral settler survivorship, mobile invertebrates are less well studied and their effects—if
any—on corals are often not known. (Williams et al. 2009, Birrell et al. 2008, Kuffner et
al. 2006, Birrell et al. 2005, Kuffner and Paul 2004).
Of the research that focuses on mobile invertebrate coral interactions, much
previous research focused on Indo-Pacific invertebrate species, especially the predatory
corallivorous crown-of-thorns starfish Acanthaster planci and gastropods in the genus
Drupella. (Carpenter 1997, Sammarco 1985). Coral reef systems in the Caribbean have
few invertebrate coral predators with such plainly visible negative effects. Caribbean
coral predators include the bearded fireworm Hermodice carunculata and the
corallivorous snail Coralliophila abbreviata. Other Caribbean invertebrate species known
to have an indirect effect on corals are the rock-boring urchin Echinometra lucunter, and
the long spined urchin Diadema antillarum (Wolf 2012, Baums et al. 2003, Bruckner et
al. 1997, Carpenter 1997, Hayes, 1990).

24
While keystone invertebrate species like A. planci in the Indo-Pacific are known
to have a direct predatory effect on corals, most invertebrates in the Caribbean, chiefly
the D. antillarum, have indirect effects on corals, such as increasing coral survivorship
through herbivory of algae. After the mass mortality of D. antillarum in 1983 and 1984,
resulting in the loss of up to 95% of the Caribbean population, a noted increase in algal
biomass took place throughout the Caribbean (Williams and Polunin 2001, Carpenter
1997). Sammarco (1985) identified echinoids as major grazers of the Caribbean up until
the D. antillarum die-off, whereas in recent years, fish have become significant algal
grazers (Williams and Polunin 2001).
Algal stressors are known to negatively influence settlement of coral larvae and
algae-dense habitats make for poor recruitment areas (Williams et al. 2009, Birrell et al.
2008, Kuffner et al. 2006, Birrell et al. 2005, Kuffner and Paul 2004). Therefore
herbivorous invertebrates are often assumed to be beneficial to coral recruitment and
survivorship in the Caribbean. The ability of mobile herbivores to influence algal
abundance through grazing—and thereby indirectly benefit scleractinian coral settlement
and survivorship—has been well studied (Coen 1988, Huston 1985, Lubchenco 1981). In
hermit crab exclusion tests, epibiont cover, specifically in the form of Dictyota spp., was
significantly higher than treatments with natural crab densities or crab inclusion
treatments, with algae increasing from 27% coverage to 77% within a single month in
exclusion treatments (Coen 1988). Edmunds and Carpenter (2001), found a significant
increase in the abundance of juvenile corals in areas dominated by D. antillarum. They
further noted a distinct decrease in macroalgae in areas with high D. antillarum densities
(Edmunds and Carpenter 2001).

25
Despite the general assumption that invertebrate herbivores should benefit corals
indirectly, invertebrate species with different anatomies, life histories, feeding strategies,
and food preferences will each have a unique effect on corals, especially when
encountering corals in their most vulnerable state as young settlers (Carpenter 1997).
Additionally, invertebrates vary in their foraging times, digestive abilities, size, speed,
nutrient requirements, reactions to altering temperature, and responses to various toxins.
These fundamental differences along with invertebrates being furthermore subject to both
bottom up and top down controls, yields different relative abundances of micro-
invertebrates with specific pressures enacted on coral settlers (Lubchenco and Gaines
1981). The complex and sensitive micro-invertebrate guild therefore holds numerous
ecologically important questions. How do various invertebrates affect coral settlement
and the survivorship of new coral settlers? Which invertebrate species hurt and which
help coral settlers?
In the present study, we investigated the impact of various invertebrate species
when introduced to coral settlers. Coral reef invertebrates tested within this experiment
included coral predators, opportunistic feeders, as well as herbivores. Two pilot studies
(see appendix) and five lab experiments were conducted with various invertebrate species
and coral settlers of the species Montastraea faveolata, Favia fragum, and Agaricia
humilis to deduce various ecological relationships. Of the five lab experiments, the first
two investigated M. faveolata larvae settlement behavior based on different invertebrate-
conditioned water and surface signals. The remaining three lab experiments tested direct
interactions of various invertebrates with settlers of each of the three coral species.
Additionally, a field experiment was carried out to examine overall invertebrate reef
traffic and the effect of varying reef traffic on newly settled F. fragum polyps.

26
Methods:
Research location
All experiments were conducted on the island of Curacao, located in the southern
Caribbean, just north of Venezuela within the chain of islands commonly referred to as
the Netherlands Antilles. Experiments were conducted between 1 September 2013 and 31
March 2014. Locations for invertebrate collections, coral collections, coral larvae
harvesting, incubations, and field experiments are shown in Figure 1.
Figure 1: Site locations. 1. Buoy Zero (12°7′25"N, 68°58′50"W) 2. Piscaderabaai
(12°7'20"N, 68°57'53"W) 3. Water factory (12°6'37"N 68°57'7"W) 4. Sea Aquarium
(12°5'3"N, 68°53'51"W) 5. CARMABI marine research station
Study species
Seven mobile, benthic coral reef invertebrate species were included in this
investigation, although not all invertebrate species were included in all experiments. The
invertebrate species of interest were: the red legged hermit crab (also known as the red
2 miles
Curacao

27
reef hermit crab or scarlet reef hermit crab) Paguristes cadenati, the red striped hermit
crab Phimochirus holthuisi, the bearded fireworm Hermodice carunculata, the yellow
corallivorous snail Coralliophila abbreviata, the rock-boring urchin Echinometra
lucunter, the long-spined urchin Diadema antillarum, and the sea lettuce slug Elysia
crispata. The three scleractinian coral species included within this investigation were the
broadcast spawning species Montastraea faveolata and the brooding species Favia
fragum and Agaricia humilis.
Experiment 1 & 2: M. faveolata settlement in response to seawater and surfaces pre-
conditioned by invertebrates:
36 polypropylene plastic beakers were cleaned with 10% dilute bleach for 1 hr,
moved into a separate rinse tank with 10% dilute sodium thiosulfate pentahydrate to
neutralize the bleach, and then rinsed with 100 m-filtered seawater (100 m FSW;
Millipore, Billerica MA/USA). A peristaltic pump was then used to prepare 0.45 m-
filtered seawater (0.45 m FSW). Each beaker was filled with 0.65 L of 0.45 m FSW.
Two microscope slides, pre-cured for four days in the CARMABI flow-through seawater
system, were then added to each polypropylene plastic beaker. The flow-through
seawater system was comprised of aquaria with 200 m 0.45 m FSW flow-through
from Piscaderabaai, pumped from a depth of 5 m.
Incubating invertebrates in the beakers with 0.45 m FSW and glass microscope
slides created conditioned seawater and conditioned surfaces for use in two separate
experiments. Two specimens of each invertebrate study species were added to each
beaker. For this experiment, four beakers were prepared per treatment. Invertebrates were
collected at 1-5 m depth from the dive sites at Sea Aquarium, Water Factory,

28
Piscaderabaai, Snake Bay, and Buoy Zero (Figure 1). In addition, eight clean glass
microscope slides were rinsed with 0.45 m FSW and placed into four beakers for a
sterile or “negative” control, and eight microscope slides pre-treated for four days in the
aquarium wet lab were placed into four beakers for a biofilm “positive” control. Both
controls had no invertebrate species present. All beakers were then placed in aquaria to
use as a water bath, stabilizing temperature at 29°C for a 24 hr incubation. In the aquaria,
beakers were assigned random locations relative to one another in space to ensure
interspersion of treatments and replicates. Beakers were placed within one of two
aquariums. In previous studies of settlement cues in pelagic marine invertebrates, a 24-
hour conditioning period was used to prepare seawater (Lau and Qian 2001, Griffith and
Frost 1976). We followed this precedent and incubated invertebrates in the beakers for 24
hr. Following this conditioning period, invertebrates were removed and the conditioned
water and conditioned glass slides were then used immediately for experiments with coral
larvae.
Experiment 1: M. faveolata settlement in invertebrate conditioned seawater
Water was pooled from each set of four polypropylene plastic beakers containing
the same invertebrate species and filtered through a 0.45 m filter. 40 ml was then added
to each of seven replicate petri dishes per treatment. There were eight treatments in total,
including one control treatment (0.45 m FSW from control with biofilm conditioned
slides and no invertebrates). Petri dishes were randomly assigned locations on the lab
bench and kept in a 12:12 night:day light regime. Lab temperature was maintained at
29°C. 30 M. faveolata larvae, collected six days prior as gamete bundles on 24 September
2013 at the Water Factory (Figure 1), were added

29
to each petri dish. Petri dishes were scored every 48 hr for settlers until day 16.
Experiment 2: M. faveolata settlement on invertebrate conditioned surfaces
Glass microscope slides were removed from polypropylene plastic beakers with
invertebrates after a 24-hour incubation period. One slide per sample was then placed in a
petri dish yielding a treatment value of nine with a positive biofilm control and separate
negative biofilm control. All treatments were replicated eight times. 35 ml of single batch
0.45 m FSW obtained fresh the same morning from the CARMABI flow-through
seawater system was added to each petri dish. Petri dishes were randomly assigned
locations on the lab bench and kept in a 12:12 night:day light regime. Lab temperature
was maintained at 29°C. 30 M. faveolata larvae, again collected six days prior as gamete
bundles on 24 September 2013, at the Water Factory (Figure 1), were added to each petri
dish. Petri dishes were scored every 48 hr for settlers until day 16.
Experiment 3: M. faveolata survivorship with varying invertebrate species:
M. faveolata larvae were reared from gamete bundles collected on 24 September
2013, from the Water Factory dive site (Figure 1). Larvae were allowed to settle on the
bottom of polystyrene plastic deli bins with lids, each filled with approximately 150 ml of
0.45 m FSW. Water changes were performed every second day to maintain newly
settled polyps. After approximately two months, the flat bottoms of bins were cut into
4x4 cm square sections while being submerged underwater to keep settlers alive. The
number of settlers on each plastic square was counted using a dissection microscope.
Squares were then incubated for 24 hr in a flow-through seawater system at CARMABI.
The number of settlers per plastic section varied from 8 to 142. Plastic sections were
grouped into groups of seven by settler density, then one plastic section from each group

30
was randomly assigned to each of eight experimental treatments. Species used in this
experiment were: the red legged hermit crab P. cadenati, red striped hermit crab P.
holthuisi, bearded fireworm H. carunculata, yellow corallivorous snail C. abbreviata,
rock-boring urchin E. lucunter, long-spined urchin D. antillarum, and the sea lettuce slug
E. crispata. Individual invertebrates were added to clear circular plastic containers of 0.5
L volume with lids. Containers were 13 cm in diameter, 6 cm in depth, with a 4x4 cm
square hole cut into the lid for water exchange. These holes were then covered with black
shade cloth (plastic mesh with 2 mm diameter holes). Controls consisted of a container
without the presence of an invertebrate. In each replicate, one 4x4 cm square of
polystyrene plastic, with settlers attached, was secured to the bottom of the container with
a plastic-coated paper clip. Paper clips were held in place with double-sided, 0.3 cm thick
poster board adhesive. Replicate containers were then submerged in aquaria with flowing
seawater for nine days. In each replicate, settler survivorship was scored 24 hr after
incubation began and then every 48 hr thereafter until the final measurement on day 9.
Experiment 4: F. fragum survivorship with varying invertebrate species:
F. fragum colonies were housed in a coral nursery that was set up on the reef at
CARMABI in Piscaderabaai. These colonies were originally collected from the Sea
Aquarium reef in December 2013. On 10 January 2014, fifteen of these colonies were
transported to the flow-through aquarium system at CARMABI.
For both Experiments 4 and 5, larvae harvesting and settlement techniques were
the same. Each coral was placed in an individual cup with a tube providing a continual
flow of a few ml of fresh seawater per second. Water overflow ran down the handle of
the cup onto a submerged 200 m plastic mesh filter, surrounded with PVC piping. As
corals planulated, larvae would rise to the surface, flow over the handle and into the

31
submerged mesh filter for collection. Aquariums with adult colonies were surrounded
with shade cloth overnight to block artificial light and promote coral planulation. At
sunrise, larvae were pipetted out of mesh catchers into polystyrene bins filled with 0.45
m FSW. Larvae were pooled over multiple days of collection to obtain enough
individuals for high replication. A mixed cohort of one- and two-day-old larvae were
introduced to settlement surfaces as daily larvae harvest rates varied. Larvae were
collected over six-days, starting eight days after the new moon. Every time 60 larvae
were collected, they were placed into polystyrene plastic bins filled with 200 mL of 0.45
m FSW. Terracotta tiles measuring 3x4 cm were incubated underwater in Piscaderabaai
for three weeks prior to the experiment, allowing the development of CCA and biofilms.
Detritus was brushed off tiles before starting the experiment. Four tiles were added to
each settlement bin.
Settlement of F. fragum varied between 2 and 16 settlers per tile. Tiles were
grouped into groups of seven by settler density, then one tile from each group was
randomly assigned to each of three experimental treatments. Species used in this
experiment were: the red-legged hermit crab P. cadenati, and the red striped hermit crab
P. holthuisi. The control treatment had no invertebrates. The experiment was conducted
in the same plastic containers used in Experiment 3. One individual hermit crab was
added to each container. One terracotta tile was then added to each container. Containers
were then submerged in aquariums with flow-through seawater for 13 days. Survival of
settlers was scored at 24 and 48 hr, and then every subsequent 48 hr until day 13.

32
Experiment 5: A. humilis settler survivorship with varying invertebrate species:
Nine A. humilis colonies were collected from Water Factory and Piscaderabaai
between 21_24 January 2014. The methods and approach used in Experiment 4 were
repeated for this experiment. Differences included testing the bearded fireworm
H. carunculata, in addition to the hermit crabs P. cadenati, P. holthuisi, and control.
Settlement of A. humilis larvae on terracotta tiles ranged from 5 to 16. Tiles were divided
among treatments using the same grouping method as in Experiment 4, resulting in nine
replicates for four treatments, control included. The tiles were scored 24 hr after initiation
and every 48 hr after that for 11 days at which point the experiment was terminated.
Experiment 6A: Time-lapse reef surveys on invertebrate reef traffic and composition:
To quantify invertebrate reef traffic and species composition, time-lapse
photography was used. Cameras used included the Canon G9, Canon G10, Canon
PowerShot S110 (all manufactured by Canon, Tokyo/Japan), and a GoProHero3+
(GoPro, San Mateo/USA). GoPro cameras include time-lapse capabilities as a
programmed feature. For the Canon cameras, publicly-available time-lapse software
known as CHDK or “Canon Hack Development Kit,” was used to program time-lapse
specifications onto memory cards, allowing for time-lapse photography with these
cameras. Diving at Buoy Zero, starting on 18 February through 29 March 2014, 40 dives
in total using SCUBA were conducted in which cameras were placed and collected.
Cameras were either placed just after sunrise so that the first shot occurred between
08:35-09:35, or just after sunset with the first shot beginning between 18:25-19:00. Time-
lapses were set to take one photo per minute for GoPro cameras and one photo per three
minutes for the remainder of cameras, due to unique camera specifications. The duration
of each time-lapse series ranged between 03:45 hr and 07:48 hr. Cameras were secured in

33
place on the reef using a 2.54 cm diameter PVC stand. Two monofilament lines were
secured to the PVC stand and hooked to reef rubble to keep cameras secure. Cameras
were placed at a depth of 5-6 m, distance to the reef face was between 10-20 m, and
camera height was between 40-50 cm from the frame objective. Two day and one
evening time series of the same location were compared over six sites for overall
invertebrate reef traffic as well as composition of reef traffic. Time-lapse series were
analyzed using ImageJ, version 1.47 with the plugin designed by Biomedical Imaging
Group Rotterdam of Erasmus MC – University Medical Center, MTrackJ, version 1.3.0.
Using MTrackJ, each photo series measurement was standardized using a ruler
photographed in the first photo of each time-lapse. All visible tracks were recorded,
regardless of when in the time series they began or ended. Tracks across time series were
standardized by taking the average number of tracks per hour for each time series.
Experiment 6B: Field survivorship of F. fragum settlers on coral reef at Buoy Zero:
This experiment was conducted to quantify the level of invertebrate traffic on reefs and
determine the effect of traffic on coral settler survivorship. 38 F. fragum colonies were
transferred from the CARMABI coral nursery located in Piscaderabaai. Colonies were
initially collected from the Sea Aquarium reef, the Water Factory reef, and Piscaderabaai.
Larvae were collected from 7-12 March 2014. Once 100 larvae were collected, they were
placed into polystyrene plastic bins filled with 200 ml of 0.45 m FSW. Prior to the
experiment, terracotta tiles measuring 3x4 cm were incubated for one month underwater
on the reef in Piscaderabaai at a depth of 5 m, allowing for the development of CCA and
biofilms. Detritus was brushed off tiles before adding four of the tiles to each settlement
bin. Tiles were scored using a blue light system. These ranged from a dive light used in
conjunction with a Fluorescence Excitation Filter, a BlueStar flashlight, or a Dual

34
Fluorescent Protein Flashlight combined with the matched barrier filter glasses
(NightSea, Bedford/USA). Settlers per tile ranged from 8 to 37 settlers. Tiles were
assigned treatments based on the same grouping methodology observed in Experiments 4
and 5. Treatment sites included three vertical surfaces and three horizontal surfaces. In
addition, one vertical control surface, and one horizontal control surface were used. Only
one control per orientation was used, as the number of tiles with settlers was a limiting
factor in the number of controls possible. For each site, six terra cotta tiles were secured
in place. Tiles were secured by placing three nails in the rock surface and placing each
tile against the rock face, wedged between the nails. This allowed for removal of tiles for
scoring purposes but also helped to keep tiles in place. Controls consisted of pieces of
steel reinforcement bar, placed in the same area but in sand instead of rock. White plastic
ceiling panels i.e., “egg crating” (Plaskolite, Columbus/USA) measuring 25x25cm was
then attached either vertically or horizontally at approximately 0.5 m above the sandy
bottom. Six tiles were then attached to each egg crate in the same fashion as other
treatments with nails. Nails were kept in the egg crating by wrapping the tip of each nail
with tape, until each nail could be wedged into a single 1x1 cm hole of egg crating. Steel
reinforcement bars for controls were used to prevent invertebrates from accessing the
tiles by keeping the egg crate surfaces off the sea floor while keeping tiles exposed to
similar abiotic conditions as other treatments. Tiles were installed on the reef at Buoy
Zero on 13 March 2014. Treatment sites with similar conditions were chosen
haphazardly. Treatment sites had a consistent depth of 5-6 m, distance to reef face 10-20
m, and with rocky bottoms except for controls. These conditions were chosen based off
the assumption that coral settlers can only settle and begin their life cycle on open and

35
solid substrate. Solid limestone areas are therefore the primary areas of interest for the
study as coral larvae are most capably of settling and recruiting to these surfaces.
Tiles were placed on designated treatment surfaces haphazardly and secured with
three nails hammered into the substrate. Tiles were scored at night after sunset using
SCUBA and a blue light system at day 0, 1, 3, 5, 11, and 16. Time-lapse cameras were set
up for all treatment sites except controls, and were the same as those mentioned in
experiment 6A. Two day time-lapses (one with tiles present, one without tiles present)
and one night time-lapse per location were recorded.
Data Analysis
For Experiments 1 through 5, a maximum likelihood approach was used. Data
were analyzed by grouping experimental treatments in various combinations and then
comparing the models to one another to find which distribution or model best described
the data (Hartmann et al. 2013, Vermeij et al. 2009, Vermeij and Sandin 2004). A
binomial error distribution was calculated across all treatments, between time zero and
the final time point. Success was defined as settlement in Experiments 1 and 2 and as
survivorship in Experiments 3 through 5. Models were synthesized with varying numbers
of parameters and groupings within parameters in an attempt to deduce the best-fit mean
values. A Chi-squared distribution was calculated between models of varying parameters
on the sum of the natural logarithm of the binomial distribution to yield the best-fit
model, assuming a single tail test. Samples throughout experiments were considered
independent and it was assumed there was no density-dependent effect of coral larvae or
coral settlers within samples. In closed system samples (Experiments 1 and 2), larvae
density did not exceed one larva per ml. In all other experiments, continuous water flow

36
and exchange was provided throughout the trial period, reducing microbial “bottle
effects” and larval density effects.
For experiment 6A, day time-lapses of treatment sites were compared to alternate
day photo series as well as an evening photo series of the same treatment site using a one-
way ANOVA to test whether there was a change in invertebrate reef traffic volume at
night. For experiment 6B, reef traffic for each time series was calculated as number of
invertebrate tracks per hour. Each area’s invertebrate traffic per hour and settler
survivorship was compared using a Kruskal-Wallis Test to determine whether settler
survivorship varied across treatment areas in relation to invertebrate reef traffic.
RESULTS:
Experiment 1- M. faveolata settlement response to conditioned invertebrate seawater
Montastraea faveolata larvae exhibited settlement over time for all treatments of
conditioned invertebrate seawater. Final settlement ranged from an average of four
settlers per sample in water conditioned with bearded fire worms, Hermodice carunculata
to nine settlers in control samples with no invertebrates (Figure 2). When applying the
maximum likelihood model, grouping the two hermit crab species Paguristes cadenati
and Phimochirus holthuisi, the control separate, and all other treatments together yielded
a significantly more accurate model than any other model P=0.002618225 (Table 1).
Additionally, there was a higher initial rate of settlement within the control treatment,
followed by that of the two hermit crab treatments (Figure 2). It should be noted that
prior to filtering invertebrate conditioned sea-water for this experiment, invertebrate
excrement and in the case of gastropods, slime, was generated within the 24-hour
incubation period. Varying levels of solubility regarding these compounds could have

37
disproportionately altered water chemical cues. The solubility of invertebrate excrement
was not measured within this study.
Table 1: Maximum likelihood model for invertebrate-conditioned seawater and
settlement of M. faveolata
Experiment 1 (Maximum likelihood model)
3-parameter model is preferred to 2-
parameter model Sum-LN(BINOMDIST) # Parameters
Likelihood for Treatment Hermits (5,6) vs.
Control (8), vs. rest (1,2,3,4,7) 119.640798 3
Likelihood for Treatment Control (8) vs.
rest (1,2,3,4,5,6,7) 124.1688386 2
Difference 4.528040618
Difference*2 (for one-tail test) 9.056081235
Degrees of Freedom 1
Chi-test P-value 0.002618225
Figure 2: Settlement of M. faveolata over time within invertebrate conditioned seawater.
0
1
2
3
4
5
6
7
8
9
10
0 48 96 144 192 240 288 336 384
Averagenumberofsettlersovereach
treatment
Time (hours)
Longspinedurchin
Sea lettuce slug
Boringrock urchin
Beardedfireworm
Red legged hermit crab
Red stripedhermit crab
Yellowcorallivorous snail
Control

38
Experiment 2- M. faveolata settlement response to conditioned invertebrate glass
surfaces
M. faveolata larvae exhibited a more narrow range of settlement over time for
conditioned invertebrate surfaces in comparison to that of conditioned seawater observed
in Experiment 1. Besides an initial high settlement of M. faveolata on conditioned
surfaces consisting of microscope slides from red striped hermit crabs P. holthuisi, all
other treatments followed similar rates of settlement, leveling off after six days and
resuming again after eight days including both biofilm negative and biofilm positive
controls. The likelihood model that was preferred was a two-parameter model in which
all treatments were grouped separate from the rock-boring urchin Echinometra lucunter,
with the next-best-fit three-parameter model not able to represent the data better
P=0.13638.
Table 2: Maximum likelihood model for invertebrate conditioned surfaces and settlement
of M. faveolata
3-parameter model is not preferred to 2-
Likelihood for Treatment long spine urchin
(1) vs. Rest (2,5,6,7,8,9) vs. fireworms &
rock-boring (3,4) 169.8667831 3
Likelihood for Treatment rock-boring
urchin (7) vs. rest (1,2,3,4,5,6,8,9) 171.5390522 2

39
Figure 3: Settlement of M. faveolata over time on various conditioned invertebrate
surfaces.
Experiment 3- M. faveolata survivorship with varying invertebrate species
Introduction of invertebrate species to M. faveolata settlers yielded variable
results. In most treatments, mortality increased except for H. carunculata and E. lucunter
where mortality rates were similar to that of the control. Additionally, in the presence of
sea lettuce slugs Elysia crispata, M. faveolata mortality actually decreased relative to the
control. Mortality of coral settlers was greatest in presence of both species of hermit
crabs (Figure 4). The exact cause in which hermit crabs were contributing to coral
mortality was not observed during the experimental period with possible mechanisms
including predation and trampling. Analysis of video recordings of separate introductions
of hermit crabs and M. faveolata did reveal incidental removal of M. faveolata by red-
legged hermit crabs P. cadenati. Additionally, a fine layer of sediment present on all
sample surfaces during the experiment was visibly absent on portions of both hermit crab
samples. These “cleaned” areas were void of previously established settlers. The long
0
1
2
3
4
5
6
7
8
0 48 96 144 192 240 288 336 384
Average#ofSettlersovereach
treatment
Time (Hours)
Long spined urchin
Sea lettuce slug
Boring rock urchin
Bearded fireworm
Red striped hermit crab
Yellow corallivorous snail

40
spine urchins Diadema antillarum, experienced mortality during the experiment and
could have contributed to the observed mortality of M. faveolata settlers. Urchin
mortality may have been a result of habitat constraints or insufficient water flow. The
maximum likelihood model favored each treatment kept separately as the model
describing eight parameters was significantly more accurate than that of a seven
parameter model P=0.009430735 (Table 3).
Table 3: Maximum likelihood model for M. faveolata settler survivorship with variable
invertebrate introductions.
8-parameter model is preferred to 7-
Likelihood for Treatment Each vs. all 1 vs.
2 vs. 3 vs. 4 vs. 5 vs. 6 vs. 7 vs. 8 448.5718432 8
Likelihood for Treatment1 vs. 2 vs. 3 vs. 4
vs. hermits (5,6) vs. 7 vs. 8 451.9415337 7

41
Figure 4: Survivorship of M. faveolata settlers, incubated with various invertebrates with
standard error shown. A. Hermit crabs B. Fireworms C. Gastropods.
Experiment 4- F. fragum survivorship with varying invertebrate species
Mortality of F. fragum increased when either of the hermit crab species was
introduced compared to the control. F. fragum, attached to terracotta tiles experienced a
higher mortality with the larger P. cadenati hermit crabs than with the smaller P.
holthuisi hermit crabs (Figure 5). Overall, settler mortality rates were lower (25 % and
below) than that experience by M. faveolata in experiment five (as high as 100%). In this
experiment, a two parameter maximum likelihood model in which the hermit crab
treatments were aggregated, did not describe the data better than when all treatments
were grouped together P=0.148493661.
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0
24
48
72
96
120
144
168
192
216
Survivorship
Time (hours)
A.
Control
Red striped hermit
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0
24
48
72
96
120
144
168
192
216
Survivorship
Time (hours)
B.
Control
Fire Worm
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0
24
48
72
96
120
144
168
192
216
Survivorship
Time (hours)
C.
Control
Sea lettuce slug
Yellow corallivorous snail

42
Table 4: Maximum likelihood model for F. fragum settler survivorship with variable
invertebrate introductions.
Experiment 4: Maximum likelihood model
2-parameter is not preferred to 1-parameter Sum-LN(BINOMDIST) # Parameters
Likelihood for Treatment control (1) vs.
hermit crabs (2,3) 27.32113134 2
Likelihood for Treatment all aggregated
(1,2,3) 28.36495982 1
Figure 5: Survivorship of F. fragum incubated with hermit crabs.
Experiment 5- A. humilis settler survivorship with varying invertebrate species
Agaricia humilis experienced increased rates of mortality under introduced
invertebrate treatments of H. carunculata and P. cadenati in relation to the control, and
interestingly less mortality when smaller P. holthuisi crabs were present (Figure 6).
0.7
0.8
0.9
1
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Coralsettlersurvivorship
Days
Control

43
Overall, mortality rates of A. humilis were similar to that of F. fragum, below 25%. The
maximum likelihood model describes the data best as a two parameter model where
controls and P. holthuisi crabs were grouped and compared to H. carunculata and P.
cadenati crabs P=0.045143297.
Table 5: Maximum likelihood model for Agaricia humilis settler survivorship with
variable invertebrate introductions.
Experiment 5: (Maximum likelihood model)
2-parameter is preferred to 1-parameter Sum-LN(BINOMDIST) # Parameters
Likelihood for Treatment control and red
striped hermit (1,4) vs. fireworm and red-
legged hermit (2,3) 83.25943908 2
Likelihood for Treatment all aggregated
(1,2,3,4) 85.26607815 1
Figure 6: Survivorship of A. humilis introduced to hermit crabs and the bearded
fireworm.
0.7
0.8
0.9
1
0 2 4 6 8 10
AverageSurvivorshipover
eachtreatment
Days
Control
Bearded fireworm

44
Experiment 6A- Reef time-lapse surveys on invertebrate reef traffic and composition
The in-situ reef monitoring experiment took place at Buoy Zero on horizontal
surfaces. Vertical surfaces were initially recorded as well, but as tiles of coral settlers
discussed in Experiment 6B were prone to excessive movement, analysis of vertical
surfaces were not included. Horizontal time series revealed a stark increase in
invertebrate reef traffic at night when compared to time-lapse series of the same locations
studied during the day (ANOVA, One-way randomized, DF = 2, F=5.513, P=0.0438,
Figure 7). Invertebrate traffic increased in areas with more hiding places, i.e., crevices,
algae, rock complexity, and sediment, and was visibly less on exposed rocky surfaces
(personal observations). The most prevalent invertebrates found during each time-lapse
series were various species of hermit crabs. The second most common invertebrates were
non-hermit crab, crab morphotypes (Figure 8).
Figure 7: Invertebrate reef traffic at three horizontal locations at Buoy Zero, standardized
as average number of tracks per hr. Control not shown as invertebrate traffic was
restricted to zero. Key: Black-Day time-lapse, Grey-Day time-lapse alternate, White-
Evening time-lapse. ANOVA, One-way randomized, DF = 2, F=5.513, P=0.0438.
0
1
2
3
4
5
6
7
8
9
Low Med/High High
Numberoftrackspertime
seriesperhr
Traffic levels at each photo quadrant location

45
Figure 8: Composition of invertebrate reef traffic on exposed rock faces for the nine time
series shown in Figure 7. Note that the nine series take place across three locations and
either after sunrise or after sunset each day (AM/PM) Key: Black- hermit crabs, Grey-
crabs, White-other invertebrates.
Experiment 6B- Reef survivorship of F. fragum settlers at Buoy Zero
Horizontally-oriented F. fragum tiles placed in heavily trafficked areas tended to
have increased levels of mortality compared to their counterparts placed in either a low
trafficked area or the control area with no traffic (Figure 9). The results were not
statistically significant when comparing each of four levels of traffic independently using
a Kruskal-Wallis Test. Grouping the low traffic site with the control together and
comparing them to the grouped data from the moderate to heavy and heavy traffic sites
still failed to yield statistical significance of P ≤ 0.05 using a one-tail Mann-Whitney U
test, however the visible difference was very close to being considered statistically
significant (U value = 43.5, P-value = 0.05262).
Unfortunately, tiles placed on vertical surfaces were prone to falling and were
found numerous times lying in the sediment upon returning to the experimental area in
0
1
2
3
4
5
6
7
8
9
(AM)#1 (AM)#1 (PM)#1 (AM)#2 (AM)#2 (PM)#2 (AM)#3 (AM)#3 (PM)#3
Numberofinvertebtrate
trackspertimelapse
standardizedfor1hr
(timelapse time) site location

46
subsequent days. A few times, damselfish could be observed knocking the vertical tiles
off the reef face. As this certainly affected survivorship of settlers on these tiles, it is
impossible to deduce what portion of settler mortality was attributed to invertebrate
traffic for vertical oriented treatment sites. Therefore, data from vertical treatment areas
were removed from analysis and only horizontally-oriented treatment sites were
considered.
Figure 9: Survivorship of F. fragum settlers on tiles located within four treatment areas
with invertebrate traffic standardized to tracks per area per hour. Key: X- Control with
zero traffic, Square- low traffic, Diamond- med/high traffic, Triangle- high traffic, Mann-
Whitney U test on site med/high and high traffic sites vs. low and zero traffic sites
yielded Z-Score =-1.6166, U value=43.5, p-value of 0.05262.
0
1
2
3
4
5
6
7
8
9
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Invertebratetrafficpertile
Settler survivorship

47
Discussion:
Settlement of coral larvae
Coral larvae are known to respond to various settlement cues including substrate
orientation, chemical cues, progeny distance from adults, and light (Marhaver et al. 2013,
Mason et al. 2011, Harrington et al. 2004, Vermeij and Sandin 2004, Carlton and
Sammarco 1987). As it has been found that a five-to-sevenfold increase in recruitment of
coral spat occurs under reduced grazing pressure (Sammarco 1985), an attempt was made
to deduce if Montastraea faveolata larvae responded differently in regards to settlement
patterns when presented with invertebrate conditioned seawater, as seen in Experiment 1.
Settlement of M. faveolata was found to increase in rate in the control treatment
(Figure 2). The likelihood model best described the data by grouping the hermit crabs and
control separately from the rest of the invertebrate treatments. This grouping could
indicate treatments with fewer chemical signals in the seawater were preferred over that
of other treatments, which were observed to have higher excrement (echinoderms and
polychaetes) and slime (gastropods) prior to particulate filtration (personal observations).
Due to the lack of clear responses to the various invertebrate conditioned seawater
treatments, our data shows that it is unlikely that M. faveolata larvae are settling based
off of unique invertebrate signatures and most likely simply choosing cleaner water in
this case.
A narrower settlement range of M. faveolata was observed under our conditioned
surface experiment and settlement began generally later in time when compared to the
conditioned water experiment (Figure 3). The maximum likelihood model favored a
single parameter model, indicating minimal differences between the various conditioned

48
surfaces. As similar settlement rates were reflected across all but the Phimochirus
holthuisi treatment, it looks as if M. faveolata does not respond directly to surface cues
left by different invertebrates. From these two experiments, these results give evidence
that this coral species may respond positively to cleaner saltwater, but does not exhibit
clear positive or negative settlement cues to these specific invertebrates found on the reef,
despite the fact that these invertebrates fulfill unique roles as predators, herbivores, and
omnivores.
Invertebrate introductions
Decapods and polychaetes
In Experiments 3 through 5, we tested various invertebrate introductions with
three coral species: M. faveolata, F. fragum, and A. humilis. In all experiments we saw a
marked decrease in survivorship of coral settlers when either of the hermit crabs was
introduced except for when P. holthuisi crabs were introduced to A. humilis, yielding an
increase in survivorship in comparison to the control (Experiment 5, Figure 6).
Although the literature regarding the effect of hermit crabs on coral settlers is
scarce, various research efforts shed light into the mechanisms in which various crabs can
contribute to coral settler death. Glynn (1997) found that bioerosion by the hermit crabs
Trizopagurus spp. on a fringing reef in Panama were responsible for the removal of about
1 metric ton of coral sediment per ha, per yr. Additionally, Glynn (1997) goes on to
discuss how hermit crabs and other crustaceans are strong enough to erode reef rock. It is
known that herbivores may contribute to coral recruitment mortality indirectly by
scraping of algae off rocks (Huston 1985), and that decapod crustaceans exhibit various
feeding behaviors including predation, detritivory, and suspension feeding (Wadell and

49
Pawlik 2000). This provides the clearest mechanism from the literature into how hermit
crabs contribute to coral settler death.
In a few instances throughout the experimental time periods, hermit crab
exoskeletons were observed after a few days. Although speculative, these observations
point to a level of malnourishment amongst the hermit crabs during the experiments. As
crabs were observed to incidentally dislodge settlers through video observations, the
mechanism of “knock off” seems to be the chief pathway in which these two species of
hermit crabs contribute to settler death of these three coral species, over the alternative of
direct predation.
Relative size of these organisms may play a role in survivorship and behavior as
well. P. holthuisi hermit crabs were smaller in size than that of the P. cadenati hermit
crabs. Measuring shell length and width in Experiments 5 and 7 yielded shell area
averages of 2.42 cm2 and 1.58 cm2 for P. cadenati in Experiments 5 and 7 respectively,
while P. holthuisi had average shell areas of 2.05 cm2 and 0.97 cm2 in Experiments 5 and
7, respectively When encountering M. faveolata settlers, P. holthuisi caused a greater
level of mortality than that of the P. cadenati (Figure 4). Conversely, when P. holthuisi
were introduced to larger settlers of F. fragum and A. humilis, a reversal was noted where
P. cadenati had a more negative effect than P. holthuisi (Figures 5, 6). P. holthuisi, in
fact, improved the survivorship of A. humilis in relation to the control, which may be in
part to their ability to navigate around these larger settlers while still maintaining a
herbivore grazing capacity. As M. faveolata settlers are tiny and smaller crabs are certain
to make shorter more frequent steps, this size effect could be a product of crab decision-
making of what to avoid on the larger end of settler size and biological mechanics on the
smaller end.

50
Looking at the results for the fireworms may also contribute insight for this
theory. While fireworms of various sizes did not exhibit a more negative effect on M.
faveolata settler survivorship when compared to the control (Figure 4), they did have a
greater negative effect when presented with the larger settlers of A. humilis in Experiment
5 (Figure 6). As H. carunculata is a known corallivorous polychaete, there may be a
threshold initial size at which their prey choice becomes worth consuming (Wolf 2012).
Our likelihood model in Experiment 5 supports this evidence as there was a notable
difference between treatments of P. cadenati and H. carunculata compared to that of the
control and red striped hermit crabs when introduced to A. humilis (P = 0.045143297).
Gastropods
While Corallophilia abbreviata had a negative effect on the survivorship of M.
faveolata coral settlers, the sea lettuce slug Elysia crispata, improved survivorship. As E.
crispata is a true herbivore and may promote coral settler health as it controls algae while
avoiding coral spat, C. abbreviata is aknown predator of adult corals, feeds on14
species of scleractiniancorals (Miller 1981). Studies onthe rate at which C.
abbreviata feedoncorals founda mean coral tissue consumptionrate of 1.9
cm2/snail/daywith a maximum of 6.5 cm2/snail/day (Baums et al. 2003, Bruckner et
al. 1997). This species is also prevalent throughout various habitats within the
Caribbean. C. abbreviata was found on 64% of coral colonies examined on a reef in
Panama (Carpenter 1997), and associated with coral mortality when corals were stressed
(Hayes 1990). Other studies conducted on Florida Keys reefs found 50% of Montastraea
spp. and 20% of Acropora palmata colonies were infested with C. abbreviata (Baums et
al. 2003). Given the fact that C. abbreviata is asignificant predator of adult corals,

51
and with our results pointingto predationof M. faveolata settlers byC. abbreviata
(Figure 4), this species maybe of greater ecological importance thanpreviously noted
as it is found widely throughout the Caribbean and has the capacity to target
scleractiniancoralsthroughout their life history.
Echinoids
One of the most widely studied invertebrates within the Caribbean is the long
spined urchin Diadema antillarum. Although in the experiment reported here, the
presence of D. antillarum led to increased mortality of M. faveolata, D. antillarum
performed poorly in the experimental setup. Individuals in some cases lost spines or died.
Results in this study concerning D. antillarum are therefore unreliable. However the
literature on these organisms is important to discuss as it covers the trade off to coral
species that can both benefit and hinder the process of coral recruitment. Research carried
out by Sammarco (1980) suggested that echinoid density can affect the success of
different coral species. Agaricia spp. was found to increase in abundance and become
dominant in areas where D. antillarum was removed (Sammarco 1980). In the same
study, the increase in Agaricia spp. in the absence of all echinoids led to a competitive
advantage over F. fragum, which saw a marked reduction in abundance. Coral diversity
has been found to be highest in locations inhabited with echinoids and lowest in areas
absent of echinoids (Sammarco 1982). F. fragum disappeared entirely from experimental
areas subjected to high urchin densities and intense grazing favored corals predominately
geared for survival in cryptic habitats (Sammarco 1980). Thus, while echinoids can create
competitive advantages for various coral species, and in some cases lead to increases in

52
biodiversity, at high densities they can become detrimental to the coral recruitment
process.
Similarly, it has been shown numerous times that low densities of echinoids leads
to favorable conditions for algae, able to then outcompete corals. D. antillarum at high
densities will exhibit strong grazing pressure, reducing both turf algae and coral spat,
while at low densities, coral spat will be overgrown by turf algae. A moderate grazing
pressure is therefore thought to be optimum for coral recruitment. (Edmunds and
Carpenter 2001, Carpenter 1997, Huston 1985, Sammarco 1980).
While our results for D. antillarum may not be reliable due to apparent stress of
individuals in the experimental chambers, mortality of M. faveolata was similar to that of
the control when introduced to a second urchin, the rock-boring urchin Echinometra
lucunter (Experiment 3). During the experiment, the urchins were observed to be very
sedentary, which agrees with literature; E. lucunter, which graze primarily on drift algae,
are a sedentary crevice dweller found in shallows and thought to only have local effects
within their burrows (Carpenter 1997, Ogden 1977).
Field experiment on reef
Invertebrate roles as predators, grazers, and tramplers may yield various benefits
and hindrances to coral settlers depending on the species of invertebrate and of the coral
in question. Although specific relationships can be observed in the lab setting, under
natural conditions, various other factors come into play such as space, algae, and top
down predation, likely to alter overall interactions from those observed under lab
conditions. On reefs for example, C. abbreviata canmost oftenbe foundbetween the
coral columns of M. annularis, where there might be some level of protection

53
(personal observations). Predators of C. abbreviata are numerous andinclude
snapping shrimp, Caribbean spiny lobster, pufferfish, hogfish, filefish, and octopuses
(Baums et al. 2003).
The time-lapse reef monitoringdone in Experiments 6B showed variable
survivorship of F. fragum settlers ontiles withinfour different treatment areas witha
range of levels of invertebrate traffic. The fieldexperiment also shows that there is a
marked increase of invertebrate reef traffic at night when comparedto the same areas
monitoredduringthe day (Figure 7). The two treatment areas with moderate to heavy
traffic yielded more variable survivorship with low survivorship of coral spat on
certaintiles when comparedto that of the control sitewithno invertebrate traffic or
site with low invertebrate traffic (Figure 9). Although sixto nine tracks per hour may
seem low, invertebrates were oftenobservedmoving extensivelywithin a small area,
counting towards a single track. If these results are extrapolatedto entirenights,
weeks, and years, the movement of invertebrates presents atangible pressure oncoral
settlers.
In addition, of all the recordedreef traffic, hermit crabs made up the largest
proportionof recordedinvertebrates, followedby other crabs and then gastropods
(Figure 8). Previous researchonCuracao reef systems found both P. cadenati and P.
holthuisi to be the dominant hermit crabspecies present onthe reefs (Jorissen 2013).
Invertebrate diversityat the species level in the present studywas difficult to deduce
as the cameraangle gave a close to 90-degree shot of eachtreatment site. Insurveys of
corals in the bay of Panama, 859 individuals representing up to 55 species of decapods
were recorded, demonstrating the diversity present within this taxon (Abele 1974).

54
Despite the overwhelming representation of decapods in this reef experiment, it was
conductedon sites characterizedby exposedrockysurfaces. If surveys were done to
include cryptic habitats, other invertebrate specieswouldmost likelybe found in
higher densities.
However, given that the dominant form of traffic onexposedrocksurfaces is
from hermit crabs, and that coral settlers inheavily traffickedareas are more prone to
mortalitythan settlers inless traffickedareas, the results of the field experiment
reflect the findings foundwithin both lab Experiments 4 and 5. When taken together,
these experiments provide strongevidence in support of the ability of hermit crabs to
contribute aconsistent negative pressure on coral spat survivorship. The adverse
response to hermit crabs is highlightedin researchonreef sponges, finding that of 30
species of sponges, 87 % produced organic extracts found to deter P. punticeps, a hermit
crab (Wadell and Pawlik 2000).
This negative pressure from various species of crabs could indicate that what is
typically considered habitat for coral settlers, is in fact not equal, based off of variable
densities of these invertebrates. Previous studies have found higher densities of decapods
in lagoons and reef slopes when compared to reef flats on three southern Cuban reefs, as
well as a strong correlation of species to hard substrate types and increasing complexity
(Martínez and Garcia 1999). Caribbean reefs have entered into an algae-dominated
phase shift and it is thought that coral recruitment strategies have changed from favorable
long-lived broadcast spawners like as Acropora sp. and M. annularis to brooding species
such as Agaricia spp. (Williams et al. 2009). By increasing complexity and habitat for
various invertebrates with algae species such as Halimeda spp., rises in invertebrate

55
densities may further reduce coral settler survivorship in those areas and provide an
additional selection mechanism to favor larger spat of brooding corals over small
spawning species.
Despite convincingresults pointingto a negative short-term interaction, it is
critical to take into consideration long-term interactions and the implications thereof.
It is known that majid crabs and echinoids preferentially feed on turf algae, known itself
to reduce coral settler survivorship (Carpenter 1997). Additionally, some Trapezia spp.
aid corals as they maintain the ability to deter coral predators (Carpenter 1997, Glynn
1983a, b). Thus, while there may be short-term pressures exhibitedbyinvertebrates on
corals, their long-term predationonalgae couldhelp promote coral recruitment.
Future studies shouldfocus onthe long-term trade-off of herbivory regarding these
invertebrate species, to that of the short-term tramplingeffect, shownhere to have a
negative impact on coral settlersurvivorship.
Conclusion:
While small hermit crabs, gastropods, and polychaetes were thought to
have minimal impact on corals due to small body size, limited numbers, and short ranges
(Carpenter 1997), both lab and reef experiments showed that invertebrates, particularly
hermit crabs, exhibited a negative pressure on coral settler survivorship. Additionally,
larger initial size of coral settlers may allow them to avoid trampling, but places them at
risk for becoming of interest to predatory polychaetes. There may therefore be a tradeoff
regarding initial size of coral settlers with invertebrate composition able to shift this
balance, thereby influencing coral health and species diversity on reefs. Additional
research on other invertebrate species, and those found within cryptic habitats, would add

56
to this picture. Micro-invertebrate traffic at Buoy Zero, although specific, highlights the
daily variability and intensity on exposed reef faces. Although micro-invertebrates
remain scarcely studied, and have yet to be considered as an important factor in coral
recruitment ecology, evidence continues to emerge on species-specific behavior and the
implications thereof.
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Acknowledgements:
I would like to foremost thank Kristen Marhaver for her consistent dedication and
support helping to not only realize this project and research effort, but her continual drive
to further my fundamental education of ecological principles and techniques found within
the scientific field of ecology at large. In addition, Mark Vermeij and Kristen Marhaver
were easily accessible, yielding a wealth of information ranging from field methods to
avenues of new research. I can’t thank them enough for making CARMABI feel like a
second home during this internship. I would further like to thank CARMABI for use of
their research facilities as well as StimulIT for taking the time to support this
investigation. Finally, I would like to thank CARMABI and DiveVersity for their help
with the logistical organization of this project.

62
Appendix:
During the fieldwork portion of this internship that occurred between 1 September
2013 and 31 March 2014, additional undertakings and projects that are not mentioned in
the above report were carried out with either my assistance or leadership. These efforts
are listed below.
-Revamped and secured additional medical supplies to bring CARMABI marine
field station up to par in dealing with emergency situations should they arise.
-Set up recycling for CARMABI marine field station so that the center could act
as a local leader in sustainable living.
-Created a coral reef husbandry protocol in conjunction with Ari Muskat for
future researcher’s efforts in maintaining coral health within the CARMABI wet
lab.
-Established a coral nursery in conjunction with Robin Hogenboom to create the
ability to research brooding coral colonies over extended periods of time and
promote the sustainable harvest of corals.
-Assisting MSc student Cas Grupstra in cage exclusion setup experiment (Dec.
2013).
-Assisting Valerie Chamberland in Diploria spawning monitoring dives (Sep.
2013).
-Setting up materials and assisting on research dives for the UvA master student
class project by Petra Nobs and Michiel Klaassen (Jan. 2014).
Pilot projects not included in above report

63
- Experiment 7 M. Faveolata Conditioned water pilot
- Experiment 8 M. Faveolata settlement and interaction test pilot
- Experiment 9 M. Faveolata 3D tile choice experiment
Experiment 7 (Pilot): Invertebrates were added to 0.45 m filtered seawater. Incubated
for 24 hr before taken out. Conditioned water was then added to 250 mL plastic bins with
M. faveolata larvae and incubated in the lab.
Expectations: Different invertebrate conditioned seawater would have an effect on the
rate of M. faveolata settlers over time.
Experimental Power: replication seven, 30 larvae per settlement bin/sample. Measured
at 36 hr and every 48 hr after that; duration eight days.
Results: Non-significant results in comparison to control except for D. antillarum
treatment. This could indicate that larvae do not make settlement choices based on water
column invertebrate signals.
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
0 18 36 54 72 90 108 126 144 162 180 198 216 234
Average#ofSettlersovereachtreatment
Time (hours)
Long spined
urchin
Red striped
hermit
Boring rock
urchin
Control
Bearded
fireworm
Sea lettuce slug

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