The Coral and Epifauna team includes three members:
Kate Semon: third-year graduate student from the University of Miami, originally from Atlanta, Georgia.
Madelyn Sullivan: Senior at Vail Mountain School in Colorado. Received a scholarship from Earthwatch to volunteer with the Bahamas team.
Melanie Silvera: Junior from Queens, New York who received a scholarship from Earthwatch to volunteer with the Bahamas team.
The team travels to various locations to survey the sites for coral and other invertebrates. We collect data from the field and enter it into a spreadsheet in order to create graphs and data tables showing the diversity of species in one area.
Objectives:
The goal of our project is to rank the health of the sites based on the presence and absence of coral and epifauna life. Generally a site with high diversity of species is a sign of a healthy and balanced environment, and low diversity indicates an unhealthy and unbalanced environment. The presence of many corals also signifies a strong marine habitat because corals are highly sensitive to any variation or change in their surroundings. We also look at diverse coral densities and colony sizes across different habitats. At the same time we collect coral colonies to determine the number of polyps per unit area of the colony thereby establishing the size the colony must reach to sexually reproduce. Polyps are the actual coral animals that “secrete calcium carbonate to form hard cups, called corallites, that proved protection for their soft delicate bodies”(Deloach, p86). Our team believes that a site with the most developed and impacted shoreline will lead to low coral densities and diversity, and that untouched and natural shorelines allow for higher densities and diversity.
Methods:
Equipment Needed
-Snorkel Gear
-Callipers
-Data sheets
-Clipboard and pencil
-Coral and Epifauna Identification books
To collect the data that we need, our team goes out to survey the specific sites between 8:30 a.m. and 2:30 p.m. All three of us snorkel around the chosen site examining both the deeper and shallower ends of the habitat. During a typical day we collect data from two to three sites. Before we start recording the species we see, we record the time of day and the type of site where we are snorkelling. The sites are located near the shores, some of which are untouched by humans, and others that are fully developed. Kate carries a clipboard with a list of common coral and epifauna, but also adds species that are not listed, but exist at a certain site.
Kate Surveying and recording the marine life.
We record the approximate number of species living in an area through a numerical system where one of a certain species found is single, 2-10= a few of a species found, 11 to 100= many of a species found, and 100+ = an abundant number of a species found. After we peruse the marine habitat we head back to the lab and enter the data into tables on the computer in order to graph and summarize our findings.
Porites furcata or Branching Finger coral
Diploria strigosa or symmetrical Brain coral
Porites astreoides or Mustard Hill coral
Siderastrea radians or Starlet coral
At some sites we collect coral colonies and determine the number of polyps per coral colony. To do this Kate disconnects corals from the reef and places them in a plastic bag, which we take back to the lab with us. We then lay the corals out and measure the individual corallites, or the individual skeletons secreted by the coral polyps. These are composed of calcium carbonate, and remain after the coral tissue has been removed. We count the individual polyps to come up with a proxy for the size a colony must reach for sexual reproduction.
Mustard Hill and Finger corals were selected
for colony measurements and corallite counts.
Melanie measured colony areas in centimetres with a pair of callipers, and counted the number of corallites per cm².
Data Summary:
A total of 21 stony coral species were observed around Great Exuma. Corals were observed in a range of consolidated near shore habitats and in differing densities, including low-density seagrass beds, moderately-dense hardbar, and highly-dense patch reefs. A comprehensive list of coral species follows.
Table 1: Observed Coral Species from Great Exuma, July 2004. Presence is denoted by a “1,” while absences is denoted by a “0.”
The team observed multiple species of corals, however some appeared more often than others. The five most common species were: Golf Ball coral (Favia fragum), Starlet coral (Siderastrea radians), Rose coral (Manicina areolata), Mustard Hill coral (Porites astreoides), and Thick finger coral (Porites porites).
The five least common species were: Thin finger coral (Porites divaricata), White Star sheet coral (Agaricia lamarcki), Fragile Saucer coral (Agaricia fragilis), Spiny Flower coral (Mussa angulosa), and Maze coral (Meandrina meandrites).
Coral species diversity was highest in the Channel Reef of Elizabeth Harbour (20 species) and near the Out Island Inn (17 species). Despite exhibiting the highest number of species, these high-density patch reefs appeared heavily impacted by development and fishing pressure. Observed symptoms included abundance of recently dead coral colonies, high algal cover, noted absence of large fishes, and presence of coral disease symptoms.
The two sites with the lowest diversity were located near Hooper’s Bay and George Divine Cay. The shores located near these hardbar sites were ranked as Medium and Severely impacted by human alteration. Hooper’s Bay has been cleared for ten years for a resort development, and no coastal setback zone exists to act as a buffer for land-based pollutants and erosion. George Divine Cay was under development on the survey date, and also included no buffering coastal setback. The surrounding marine environment was heavily impacted by siltation due to poorly-placed sediment catchments. A fine layer of sand was observed covering all corals and sea life in the area. Recently-dead coral colonies were observed in both sites.
An overall trend was observed for coral diversity located near impacted coastal zones, and is illustrated in the following figure. The highest average numbers of stony coral species were observed in marine environments located near “Low” and “Medium” impacted coastlines. Marine environments near “High” and “Severe” impacted coastlines showed a low diversity of coral species. The highest average number of stony corals was observed in “Medium” impacted sites.
Average Number of Coral Species located near Ranked Sites
Fire Coral and Sun Anemones
were commonly observed in Great Exuma coral
habitats.
A total of 104 species of Epifauna were observed in surveys around Great Exuma. These species represented six phyla, and included sponges, jellyfish, hydroids, stony corals, soft corals, anemones, tunicates, echinoderms, molluscs, crustaceans, and annelid worms.
Percent composition of each Epifauna group was determined for marine habitats located near representative Low, Medium, High, and Severely-impacted coastlines. Examples of Epifauna composition follows.
Low-impact sites often hosted a high diversity of sponges, soft corals, and hard corals.
Percent Epifauna Composition in a low-impact site, Sand Dollar Reefs
Sponges often dominated Medium-impact sites, while hard and soft corals appear less diverse.
Percent Epifauna Composition in a medium-impact site, Red and Green Channel Marker Reefs
Annelids and sponges were most diverse in marine environments located near High-impact sites. Jellyfish and hydroids also begin to play a larger role in community composition.
Percent Epifauna Composition in a high-impact site, offshore from Georgetown Administration Building
Sponges and hard corals may be diverse in severe sites, while soft coral diversity is low compared to soft coral diversity in other sites. Jellyfish and hydroids also exist in higher diversity than Low or Medium-impact sites.
Percent Epifauna Composition in a severe-impact site, George Divine Cay
Conclusions:
Ø Coral diversity is negatively affected by coastline development. Coastal zones ranked as “High” or “Severely” impacted by human-caused environmental change were associated with a low diversity of stony coral species.
Ø Coral diversity was slightly higher in “Medium” impact environments than “Low” impact environments. This is finding is consistent with the theory that highest community diversity will be supported in habitats subject to frequent disturbance.
Ø Epifauna community shifts are evident in association with coastline development. The most diverse epifauna groups were different in Low and Medium impact environments than in High and Severe impact environments. Soft corals appeared most sensitive to coastal development.
Deloach, Ned and Paul Humann. Reef Coral Identification. New World Publications, Inc.: Jacksonville, Florida, 2002.