Graduation Year

2015

Document Type

Thesis

Degree

M.S.

Degree Name

Master of Science (M.S.)

Degree Granting Department

Marine Science

Major Professor

Albert C. Hine, Ph.D.

Committee Member

David G. Zawada, Ph.D.

Committee Member

Stanley D. Locker, Ph.D.

Keywords

coral reef, density, Dry Tortugas, population ecology, spatial patterns

Abstract

Acropora cervicornis was once one of the dominant reef building corals of the Caribbean, Florida Keys, and Dry Tortugas (DRTO), but since the 1970’s populations have been decimated throughout their geographic range. Recently, a repopulation was documented through detailed benthic surveys conducted by the U.S. Geological Survey at three locations (Pulaski Shoal, East Key, and Loggerhead Key) within DRTO. Benthic surveys using the U.S Geological Survey’s Along-Track Reef Imaging System (ATRIS) revealed hundreds of previously undocumented colonies.

These discoveries have provided a unique data-set, allowing a comparison between the historical (1883, 1976) and contemporary distributions (2009, 2011) of A. cervicornis. Kernel density estimates were used to analyze shifts in high density areas and non-parametric multivariate analysis of variance tests were used to analyze differences between years in location and extent of the distribution. The results from the KDEs indicated high density areas have shifted among year’s at all three study areas. The comparison of the location and extent of the historical and modern A. cervicornis distributions revealed similarities and differences among years that varied among the study areas. This information is important to the management of this species because it provides vital information on the extent and location of the current distribution relative to historical levels. This study also provides documentation of the population dynamics and ecosystem changes over large time scales within the DRTO region.

The above mentioned dataset was also used in a second study to quantify 1) variations in density among factors such as location (study area), suitable habitat type, and water depth, 2) overall spatial population patterns, and 3) spatial patterns in A. cervicornis density. Results indicated population structure was significantly clustered (P = 0.001) at Pulaski Shoal and Loggerhead Key with areas containing hotspots or significantly higher density (P < 0.05). Although significant hotspots existed, density did not significantly differ among suitable habitat types. Compared to all other factors, water depth had the largest effect on the variation in mean density of A. cervicornis. These findings are vital to understanding the recovery of this species in terms of current habitat and depth associations.

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