1. Introduction Intermediate Disturbance Hypothesis Definition : Both high and low levels of disturbance will lead to reduced diversity in communities, where maximum species diversity will be found in intermediate levels of diversity (Molles 2002). Low Disturbance : species diversity limited by successful competitors. High Disturbance : The community will consist only of those species that can colonize and complete their life cycles between disturbances Caribbean coral reefs have suffered massive disturbances that have affected coral species diversity (Buddemeier et al 2004). Natural Disturbances Hurricanes, El Niño, climate changes Caribbean-wide bleaching caused by El Niño in 1998 Diseases Mass Diadema antillarum die-off in1983-84 Allowed algae and phytoplankton to bloom and overgrow the coral Mass Elkhorn ( Acropora palmeta ) and Staghorn ( A. cervicornis ) coral die-off due to White Band disease Major reef builders in Caribbean Disease introduced in 1972 and has changed coral community structures Human Disturbances Sedimentation and nutrient loading from freshwater runoff Direct destruction of reefs and coastal habitat modifications Overfishing This study observed the species composition and percent coverage of stony corals at three reefs in Caribbean located near the islands of St. Vincent and the Grenadines. These reefs differ in their exposure human disturbances. The first site being a part of the Tobago Cays Marine Park, created in 1998, is being considered as the least impacted by humans. The second site, considered moderately impacted, is located off the coast of the populated island of St Vincent. The third site is considered the most heavily impacted and is located near the mouth of a river from the Wacumet Valley in St. Vincent. Species composition and percent coverage of stony corals in three Caribbean reefs in St Vincent and the Grenadines Melissa Shelley Dept. of Biological Sciences, York College of Pennsylvania Results Acknowledgments I’d like to thank Jason Buchheim and Odyssey Expeditions for allowing me to perform this research while participating in their program. I’d also like to thank Jason Buchheim, Jeni Kovac, and Devon Crippen for helping collect the data needed. I am also thankful for all the advice and guidance provided by Dr. Jessica Nolan throughout the entire thesis process. At Depth: 60 ft Swim five kick strokes in random direction along reef with eyes closed Set end of chain down and lay chain across coral Count number of chain links covering each species of stony coral *excluding dead or bleached corals* Repeat procedure five more times at same depth Repeat entire procedure at depth of 20 ft Ho: There will be no difference in coral diversity, evenness, richness or percent coral coverage between the three sites or between the two depths Procedure Data collected August 2007 Materials 46’ Catamaran Dive Gear Two teams of two divers 6 Transect lines (210 links at 2cm per link) Coral Identification Chart (Humann and Deloach 2002) Species Diversity No significant differences were found in species diversity over the three sites No significant differences between depths at each site Species Evenness No significant differences were found in species evenness over the three sites No significant differences between depths at each site Species Richness No significant differences were found between depths at each site Site 2 was significantly different from Site 1 and Site 3 at 60 ft Site 3 was significantly different from Site 1 at 20 ft Results No change in coral diversity, evenness, and percent coverage was found. Overall there were small differences in the three sites for species richness. Site 2 had greater species richness than either site 1 or site 3 at 60 ft Site 1 had the lower species richness at 20 ft than Site 3. Discussion Few significant differences were found between sites. The data did not clearly establish a relationship between the believed levels of human disturbances of the three sites and the species composition or percent coverage of stony corals. Site 1: Site 1 was formed into a marine park in 1998. The short time span that has elapsed may not have allowed corals to fully recover from previous natural and human disturbances. Corals take an estimated 15-20 years to recover from disturbances (Hughes and Connell 1999). This suggests that Site 1 may have been more impacted than previously expected. Future studies that might be conducted might include the following : Survey algal abundance and coral abundance to determine correlation between algal and coral communities. Continue surveying reef structures over a longer period to determine the relative importance of large-scale natural disturbances and smaller-scale human disturbances. Sites Site 1: Horseshoe Reef, Tobago Cays Fringing barrier reef located within Tobago Cays Marine Park (established 1998) Site 2: Orca Point, St. Vincent Fringing reef located near island shore Site 3: Bat Cave, St. Vincent Fringing reef located near island shore and river in the Wacumet Valley Percent Coral Coverage The data was transformed with an arc sin square root (x) No significant differences were found in percent coverage over the three sites using a two-way ANOVA statistical test and a Bonferroni post-test No significant differences were found between depths at each site The bars on this graph represent the mean and the error bars represent the standard error of the mean (SEM) Image courtesy: http://www.grenadine- sailing.com/images/map.jpg Photo courtesy: http://www.divestvincent.com/JPEGS/07BatCave432.jpg Scanned image courtesy Molles 2002 Work Cited Buddemeier, R.W.; Kleypas J.A.; Aronson, R. B. 2004. Coral reefs and global climate change: potential contributions of climate change to stresses on coral reef ecosystems. Pew Center on Global Climate Change. Hughes, T. P. and Connell, J. H.. 1999. Multiple stressors on coral reefs: a long-term perspective. Limnology and Oceanography. 44:932-940. Humann P. and Deloach, N.. 2002. Reef Coral Identification: Florida, Caribbean, Bahamas. New World Publications. Molles, M. C.. 2002. Ecology: Concepts and Applications. McGraw Hill Publication. Second edition.