Wee Wee Caye Coral Reef Population Dynamics Study
Forrest Ashworth, Jade Lu, Garrett Powell
Belize Miniterm 2013
Schmalbeck/Halpin
Abstract
Wee Wee Caye, located nine miles off the coast of southern Belize in the Sittee
district houses a small but extremely diverse portion of the barrier reef (Latitude :
16.750, Longitude : -88.133). In coral reef ecosystems, species diversity and
population density depends on permanent residents of area in addition to passing
organisms. We decided to explore variance in community dynamics of a specific
coral reef head between daytime and nighttime. We first selected a representative
coral head and then observed this head both afternoon and night for five days. From
our observation and analysis we drew two primary conclusions: (1) higher species
diversity was observed at the site during the daytime compared to nighttime, and
(2) some species were observed to have a permanent residence in our site while
others merely visit on a temporary basis.
Introduction
The Belize Barrier Reef is home to hundreds of different species of fish, coral,
sponge, and other marine creatures. A hub of extreme species diversity, this reef is
the largest in the Western Hemisphere and invaluable to the marine ecosystem. Wee
Wee Caye, located nine miles off the coast of southern Belize in the Sittee district
houses a small but extremely diverse portion of the barrier reef (Latitude : 16.750,
Longitude : -88.133). This small island is entirely covered in mangroves and
inhabited solely by the marine research lab. Extreme care has been taken minimize
environmental impact on the mangrove habitat and the marine ecosystem
surrounding the area. As wildlife experiences minimal impact from humans, the
caye is an ideal research location to explore the community dynamics of the reef.
Community dynamics of ecosystems in general have been found to vary with
season, weather, and time of day. The species diversity and population density
depends on permanent residents of area in addition to passing organisms. We
decided to explore variance in community dynamics of a specific coral reef head
between daytime and nighttime.
The coral reef we selected to study contained six sea fans, two green finger
sponges, two sea plumes, two star horseshoe worms, one feather duster worm, six
rock urchins, two pencil urchins, and a base of round starlet coral.
Materials and Methods
Materials:
 1 buoy
 1 weight
 1 rope
 2 underwater flashlights
 2 stopwatches
 Snorkel gear
Methods:
Reef Selection:
The first part of our study was to pick the right coral head that we needed to study.
We did this by first swimming around the entire island and seeing the types of coral
and fish that occupied the area. After we had a good idea of what the common types
of coral, sponges, and wildlife looked like we then started scouting for our coral
head. We decided upon the location of our coral head because we believed that it
covered all the makeup of the island well. We also chose the location because the
tide was not strong during the day or night making it easier for our team to observe
the location.
Daylight:
Our team researched the population dynamics of a coral head studying daytime
versus nighttime. During the day when the sun was bright at 1:30pm our team
swam out to our buoy that was placed about 10 feet away from the coral head we
were studying. We did this to minimalize disruption of the habitat to make sure that
we didn’t scare any of the wildlife that inhabited our coral head before we started
observing. After we reached the buoy we started our timers and went to our coral
head. Each member of the group had a position to observe the coral so that we did
not miss noting any changes that might have arisen. We observed the coral for five
minutes and then reconvened at the buoy and talked about what we had seen. Once
we got back to the dock we wrote down descriptions of what we had seen to identify
later.
Nighttime:
To observe our coral head at night our team made sure the sun was down for at
least 45 minutes and we decided that 6:45 was a good time to dive. We would again
get to our buoy that was 10 feet away from our coral head and start our timers. This
time though we only had one flashlight so instead of three separate positions
around the coral head the team circled the coral head together for five minutes. We
then again went back to our buoy and discussed what we had seen and headed back
to the dock. Once at the dock we then again wrote down the descriptions of what we
had seen to identify at a later time.
Identification:
After we had observed our coral head and written down the descriptions of what we
had seen we had to identify all the species we had seen. Since we did not have
Internet access on the island we had to use books and educated persons around the
island to identify everything. The main books we used were “A Field Guide to Coral
Reefs Caribbean and Florida” by Eugene H. Kaplan, “Reef Creature Identification of
Florida, Caribbean, and Bahamas” by Paul Humann and Ned Deloach, and “Reef Fish
Identification of Florida, Caribbean, and Bahamas” by Paul Humann and Ned
Deloach. After looking through the books if our team could still not identify
something we would ask our island expert what we had seen. After identification we
compiled a data table of what we had seen.
Results
Figure 1.
Average species sightings per day
1.4
1.2
1
0.8
0.6
0.4
Average sightings per day
0.2
0
Figure 2.
Average species sightings per night
1.4
1.2
1
0.8
0.6
Average sightings per night
0.4
0.2
0
4-Eyed Reef Slippery dick
Octopus
Doctorfish
Barrucuda
From comparing Figure 1 and Figure 2 above, we can see that far fewer species
visited the coral head at night compared to during the day. There is overlap,
however, between the two time points observed. It is also shown in the graphs that
some species are more regularly seen at the site.
Discussion
From our data shown in Figures 1 and 2, we can draw two basic conclusions:
(1) higher species diversity was observed at the site during the daytime compared
to nighttime, and (2) some species were observed to have a permanent residence in
our site while others merely visit on a temporary basis. We conclude from the
average number of sightings we observed that our site was home to a 4-Eyed Reef
Octopus, a Doctorfish, and a Fairy Basslet. Of these species, the octopus was
constantly at the site both day and night. The Doctorfish was seen almost every
night, but less frequently during the daytime. We hypothesize that this is because
the Doctorfish travels during the day (scouting for food, mates, etc.) and then sleeps
in our site. The Fairy Basslet was seen almost everyday, but was not seen at night.
We hypothesize that the Fairy Basslet was indeed there sleeping at night, however,
we did not observe it because it is a small fish and probably sleeps deep within the
base of starlet coral that we cannot observe. Shown below are the permanent
residents of the coral head.
Reef Octopus
http://www.flickriver.com/places/The+Bahamas/Cat+Island/
Doctorfish
http://www.flmnh.ufl.edu/fish/Gallery/Descript/DrFish/Doctor.htm
Fairy Basslet
http://www.daveread.com/tripreports/roatan/september2000/september
2000.html
Going back to Figures 1 and 2, the remaining species that were not concluded
to be residents of our coral head can be concluded to be visiting species. This
includes an arrow crab, a Schoolmaster fish, slippery dicks, and a 4-Eye Butterflyfish
during the daytime. At nighttime, the visitors were found to be slippery dicks and a
barracuda. Although the average sightings per day/night for the slippery dicks are
comparable to those of other resident species, we observed these fish coming and
going during our observation time. This leads us to the conclusion that the slippery
dicks are not permanent species of the coral head.
The visiting species compared between day and night primarily visit during
the day as discussed above. We hypothesize that this could be for two reasons: (1)
there are more active species during the day as compared to the night in our area,
and (2) marine organisms can experience sun damage and therefore flock to shaded
areas such as coral heads during the day. Species diversity in our coral reef can be
accounted for by the shallowness of the ocean in the area (Noble et al).
Although these conclusions follow our data for the specific head of coral reef,
they cannot be generalized for the entire marine ecosystem. Only 5 trials were
performed for the daytime and only 4 were completed for the nighttime. Many more
trials are needed to ensure significance of data. The method of data collection was
also flawed in that our presence around the reef most likely deterred visiting
species and caused resident species to hide in the coral out of sight. An
inconspicuous underwater camera could fix plausibly fix this problem. Observing
more than one plot would also significantly improve the accuracy of our
conclusions. The transient nature of fish species in coral reef ecosystems has been
been noted as a source of error in these articles (Hixon).
Conclusion
From the results that we collected our team found that at one coral head fish were
more active during the day than at night. We concluded this because we found that
during the day some species lived at the coral head and were always around while
others were just passing through. Yet, during the night mainly only the species that
lived at the coral head were present. We account this because fish during the day are
near the coral head trying to shield themselves from sunburn while at night they do
not have to worry about this problem. We also hypothesize that this is due to more
species active in the daytime rather than at night. This research was only over a
short time span of five days and four nights. To be more precise with the
information this study would have to be conducted over a longer span of time and
go into more detail to see if our conclusions hold true. Most other related studies
and articles span over a much longer time and are observations of a more expansive
area.
Literature Cited
Hixon, Mark A. "Population Dynamics of Coral-reef Fishes: Controversial Concepts
and Hypotheses." Wiley Online Library. Australian Journal of Ecology, 28 July
2006. Web. <http://onlinelibrary.wiley.com/doi/10.1111/j.14429993.1998.tb00720.x/abstract>.
Humann, Paul, and Ned DeLoach. Reef Fish Identification: Florida, Caribbean,
Bahamas. Jacksonville, FL: New World Publications, 2002. Print.
Humann, Paul, and Ned DeLoach. Reef Set: Your Eyes to the Sea. Jacksonville, FL: New
World Publications, 2008. Print.
Kaplan, Eugene H. A Field Guide to Coral Reefs: Caribbean and Florida. Boston:
Houghton Mifflin, 1999. Print.