<p> A study of two shallow fringing reefs off the coast of Zanzibar Island was conducted. The study site was Grave Island, 1 km off the shore of Zanzibar town. The comparison site was Chumbe Island, 10 km upcurrent of the town, adjacent a less densely inhabitated coast. The major anthropogenic stress on these reefs could be considered nutrient loading from sewage discharge.</p> <p> Studies of the sea urchin Diadema setosum, indicated mean densities at Grave Island of 6.4 urchins/m^2 and 1.2 urchins/m^2 at Chumbe Island. Urchin densities comparable to those at Grave Island have been related to overfishing and reduced coral recruitment. Coral associate densities were also considered with a mean density of 87/m^2 at Grave Island and 31/m^2 at Chumbe Island. High coral associate densities have been linked to structurally and physiologically weakened coral.</p> <p> Transect studies were conducted and suggested there were significantly reduced coral cover and reduced amounts of live coral at Grave Island (cf Chumbe Island). As well, coral species diversity was significantly lower at Grave Island than at Chumbe Island. Lowered species diversity suggests an unstable community structure, and reduced coral cover may indicate a faltering reef.</p> <p> Stable Isotope studies were conducted on tissue samples from both sites. They showed no significant difference.</p> <p> This study reflects the poor health of Grave Island. The high abundance of urchins and filter feeders, combined with reduced coral cover and diversity, suggest high nutrient loading on these reefs. The high abundance of urchins and associates also suggest coral mortality will be high and recruitment low. If these trends continue, it is unlikely the reef at Grave Island will be able to survive.</p> / Thesis / Bachelor of Science (BSc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/19293 |
| Date | 04 1900 |
| Creators | Dunn, Jennifer Judith |
| Contributors | Risk, M. J., Geology |
| Source Sets | McMaster University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis |
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