Date of Award:

12-2008

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Geosciences

Department name when degree awarded

Geology

Committee Chair(s)

W. David Liddell

Committee

W. David Liddell

Committee

Carol M. Dehler

Committee

Nancy O. Mesner

Abstract

In 1988 data on coral reef community composition were collected from two areas, Akumal and Chemuyil, Quintana Roo, Mexico, ranging from 5-35m depth. These areas were revisited in 2005 and data were collected by the same methods and at the same depths as in 1988. Data from 1988 and 2005 were compared to determine if the coral reefs had undergone significant changes, and what specific changes had occurred. Chi-square analysis determined that community composition data collected in 1988 are significantly different from data collected in 2005 at all sites and depths within the categories of corals, gorgonians, sponges, and macroalgae. Mann-Whitney U analyses were performed on abundance data for coral, gorgonians, sponges, macroalgae, crustose coralline algae, erect coralline algae/calcareous algae, filamentous/multi-species turf algae, and non-living substrate. Results from the Mann-Whitney U analysis varied between sites; however significant trends of increasing macroalgae, crustose coralline algae and filamentous/multi-species turf, and declining non-living substrate were observed at almost all sites. H' biodiversity indices J' evenness values and species number (S) were calculated for all sites over the two time periods, with no discernable trends observed. Increases in crustose coralline algae and filamentous/multi-species turf algae suggest that eutrophication and overfishing may be responsible for the trends observed on the reefs at Akumal and Chemuyil. Anecdotal accounts also suggest that eutrophication from septic water flowing through the highly porous karst limestone of the Yucatan Peninsula may be the largest malefactor causing the observed changes. The increase in filamentous/multi-species turf algae exhibited by the data suggests that eutrophication is predominantly responsible for the alternate states of the reefs. Furthermore, evidences indicative of other forms of stress on the reefs, such as bleaching, scraped or broken coral heads, disease, and sedimentation, were rarely observed.

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