Term of Award

Spring 2002

Degree Name

Master of Science

Document Type and Release Option

Thesis (restricted to Georgia Southern)

Department

Department of Biology

Committee Chair

Daniel F. Gleason

Committee Member 1

Alan W. Harvey

Committee Member 2

Bruce A. Schulte

Abstract

High intensities of ultraviolet radiation (UVR) have been shown to detrimentally effect the growth, reproduction, and photosynthetic physiology of corals inhabiting tropical marine waters. One protective mechanism utilized by marine organisms, including corals, is the production of mycosporine-like amino acids (MAAs) that absorb biologically harmful wavelengths of UVR in the range from 309 to 360 nm. Normally present within animal tissues, MAAs have also been extracted from mucus present on colony surfaces. Many functions, including protection from sedimentation, salinity fluctuations, and temperature changes, have been attributed to coral mucus. The presence of MAAs within mucus suggests an additional function: protection from the biologically damaging effects of UVR. Therefore, the goal of this study was to evaluate the UVR protective capabilities of coral mucus and its constituent MAAs in situ by addressing three main questions. First, what are the UVR absorption capabilities of coral mucus? Second, is mucus production affected by exposure to UVR? And finally, do MAA concentrations within mucus vary with changes in UVR exposure?

Colonies of Porites astreoides located at Rainbow Gardens (23.47.783N, 76.08.787W) and North Norman's (23.47.373N, 76.08.267W) patch reefs adjacent to Lee Stocking Island, Bahamas were either exposed to, or protected from, ambient UVR for 45 days. Mucus and tissue samples were collected at the beginning and end of the experiment and mucus production was measured by mucus weight while absorption of UVR by mucus and tissue samples was analyzed using spectrophotometry.

Neither mucus production nor MAA concentrations were affected by UVR exposure at ambient levels. However, coral mucus and associated MAAs absorbed 1.11% of the total UVR impinging on coral surfaces with the highest absorbance in the UV-B (280-320 nm) portion of the spectrum. Surprisingly, the mean percent absorbance of MAAs extracted from mucus was not significantly different from that of mucus and MAAs combined. These results indicate that any UVR protection provided by coral mucus is furnished primarily by MAAs rather than inherent properties of the mucus. Finally, mucus MAA concentrations were not dependent on tissue concentrations. In sum, coral mucus and associated MAAs do provide small amounts of UVR protection, but it is unlikely that mucus and its constituent compounds have been selected as a primary mechanism to prevent UVR damage.

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