Marine Science

Marine Science

Senior Theses 2003

Safiya F. Sawney (2003). Temperature and coral bleaching: experiments on the role of temperature in reinfection, and the effect of nitric oxide synthase inhibitor
Faculty Advisor: Joel Thompson


Coral bleaching involves the loss of algal pigment and/or zooxanthellae from the coral. In recent years this phenomenon has escalated globally resulting in the death of many coral reefs and the biological communities they support. Coral bleaching also threatens the social and economic welfare of many tropical island nations. Global warming and increased El Nino Southern Oscillation (ENSO) events have contributed to coral bleaching and will continue to be significant contributors in the future. A membrane permeable nitric oxide synthase inhibitor, 7-nitroindazole, was administered to corals to examine whether a decrease in the NOS activity of heat stressed zooxanthellae of Madracis mirabilis will stop coral bleaching, since elevated NOS activity has been associated with temperature induced stressed of zooxanthellae. Also, the effect of temperature on the re-infection of bleached Aiptasia pallida by their expelled symbiotic zooxanthellae was examined. This experiment also examined the effect of temperature on the productivity of expelled zooxanthellae. The results from the nitric oxide synthase experiment were inconclusive and further characterization of zooxanthellae NOS activity is necessary. There was significant re-colonization of bleached A. pallida at their ambient temperature (23°C) and at 28°C while A. pallida at the stress temperatures (10 and 15°C) did not show significant re-colonization. Therefore, recovery of A. pallida is successful within their normal temperature range and unsuccessful at stress temperatures. Re-colonization was not influenced by productivity of the zooxanthellae. Further exploration of the relationship between elevated nitric oxide synthase activity and coral bleaching can help us explore the idea of using NOS as a biological indicator of coral health in the future as sea surface temperatures increase. Results from the re-colonization study help us understand ways in which corals recover and acclimate to climatic changes, especially the increase in sea surface temperature associated with ENSO and global warming events.

Student Research