1. Assessing stress responses of the tropical coral, Siderastrea radians,
to simulated parrotfish feeding in a Belizean reef ecosystem.
Hayley Powers and Kyle Phillips
Department of Biology, University of Wisconsin-La Crosse, La Crosse, WI
INTRODUCTION
• Siderastrea radians is a golf ball-sized coral
found throughout a number of microhabitats in
the Belizean reef ecosystem
• Coral samples around 5 cm. in diameter were
collected from the South turtle grass beds on
South Water Caye, Belize (Fig. 2)
• Each sample was taken back to the lab (Fig. 1B)
and placed in 650mL containers
• All samples were given two hours to acclimate to
their new environments
FIELD COLLECTIONS
• Siderastrea radians samples were separated into six
blocks containing three individual colonies per
block
• Within each block, one coral was scratched (to
simulate predatory feeding) (Fig. 3A), one was
brushed (non-predatory contact), and one was left
untouched (control)
• Each stimulus was applied to a row of ten polyps
per colony
• Tentacle and mouth extension was recorded for
each coral at 0, 10, 20, 30, 60, and 90 minutes
• Tentacle and mouth extension was observed not
only at the site of the observed stimulus but also on
the adjacent row of 10 polyps using a dissecting
scope (Fig. 3B)
METHODS
RESULTS
RESULTS AND DISCUSSION
ACKNOWLEDGEMENTS
EXPERIMENTAL TREATMENT
• Overall functioning of reef ecosystems can be
estimated by assessing coral health within the
system
• Numerous organisms, including parrotfish, feed
on coral (such as Siderastrea radians) and
therefore may influence coral health
• Parrotfish are abundant in the Belizean reef
ecosystem
• Parrotfish feed by scraping off living polyps and
also pieces of the CaCO3 skeleton
• Little is known about how coral responds to this
predation
• To determine the localized response of S. radians
to simulated parrotfish predation.
A
B
FIGURE 3. (A) Scratched sample of S. radians, and (B) Microscopic
view of a scratch on S. radians sample.
• Thank you to Dr. Greg Sandland, Dr. Gretchen
Gerrish, and Pete Alvilez for their guidance.
FIGURE 1. (A) Siderastrea radians and (B) The Belizean lab bench
• The effects of non-predatory contact, often made
by divers, is even less studied than other
interactions, but poses major questions in high
tourism traffic reef ecosystems, like South Water
Caye (Fig. 2)
FIGURE 2. View off the south beach of South Water Caye.
A B
OBJECTIVE
FIGURE 4. (A) Number of tentacles extended per colony row over time.
(time × stimuli F6.0,45.1 = 4.08, P = 0.002) (B) Number of tentacles extended
adjacent to colony row over time (time × stimuli F5.7,42.4 = 1.98, P = .093)
FIGURE 5. (A) Number of mouths opened on colony line over time (time ×
stimuli F4.5,33.7 = 2.38, P = 0.065) (B) Number of mouths opened adjacent to
colony line over time (time × stimuli F4.4,33.1 = 3.52, P = 0.014)
• The magnitude of the stimulus influenced the
time it took polyps to reemerge along and
adjacent to affected rows (Fig. 4A&B, 5A&B)
• Polyp response suggests that parrotfish
predation may have a negative impact on corals
and therefore reef health
• To further understand the effects of feeding on
corals, future studies should aim to assess how
widespread polyp responses are across a colony
• If the response extends beyond the impacted
area, it raises an important question: what are
the energetic costs of such a disturbance for the
colony
A B
A B
0
2
4
6
8
10
12
0 20 40 60 80 100
TentaclesExtendedAdjacent
Time (min)
TENTACLE RESPONSE
0
2
4
6
8
10
12
0 20 40 60 80 100
TentaclesExtendedonLine
Time (min)
• Control
☐ Brushed
− Scratched
0
1
2
3
4
5
6
7
8
0 50 100
NumberofOpenMouthsAdjacent
Time (min)
• Control
☐ Brushed
− Scratched
0
1
2
3
4
5
6
7
8
0 50 100
MouthsOpenonLine
Time (min)
MOUTH RESPONSE