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Senior Theses 2007
Jessie Drechsel (2007). Effects of atrazine-induced bleaching on the zooxanthellae of the hard coral Madracis mirabilis: evaluation of flow cytometry as a means of profiling zooxanthellae during bleaching events
Faculty Advisor: Peter Meylan
Regional coral bleaching events are on the rise throughout the tropics. While much is being done to determine the mechanisms associated with this dissociation of corals' zooxanthellae, there is still a great deal left to determine. The purpose of this study was to further investigate the effects of chemically induced bleaching on coral, specifically by observation of the scleractinian Madracis mirabilis treated with the photo system II herbicide atrazine. This study also served as an exploration of the use of flow cytometry in the observation of in situ and expelled zooxanthellae during chemically induced bleaching events, with hopes of supporting the suggested utility of this tool in the investigation of coral bleaching mechanisms. 3 ppm atrazine was observed to have the most rapid effect on M. mirabilis' maximum potential quantum yield (MPQY). Coral fragments treated with 3 ppm atrazine for just one to four days showed significant recovery upon their first day of removal that did not differ significantly between the days of removal; however, after 5 days of treatment, recovery of MPQY was not observed.
Flow cytometry proved an effective means of investigation of both in situ and expelled zooxanthellae, and would very likely prove even more useful if combined with the use of more advanced flow cytometry techniques, such as fluorescent tagging. Photo system II herbicides', such as atrazine's, effects have been well documented in the laboratory and support efforts and conservation that works to remove these pesticides from the marine community.