Graduation Year

2008

Document Type

Thesis

Degree

M.S.

Degree Granting Department

Marine Science

Major Professor

Pamela Hallock Muller, Ph.D.

Keywords

Bioindicator, SEDCON, FORAM, Carbonate, Coral

Abstract

Coral cover remains highest on patch reefs at the northern end of the Florida reef tract. The reasons for this trend are not well understood, but may be related to the protection from extreme variations in water quality parameters provided by the near constant presence of islands at the north extent of the Florida Keys. Three indices have been developed based on Foraminifera and sediment constituents. Two of the indices, the FORAM Index and the SEDCON Index, were developed to indicate the suitability of a reef environment for continued reef accretion. The third index, the Photic Index, is an assessment of photic stress on reefs based on incidence of bleaching in a species of Foraminifera, Amphistegina gibbosa, which is known to experience loss of algal endosymbionts similar to bleaching in corals. Patch reefs were sampled in Biscayne National Park, FL to assess sediment characteristics and foraminiferal assemblages, as well as to examine trends in the three indices.

Sediments associated with a majority (59%) of reefs were coarse sands; muddy sediments were restricted to a few inner patch reefs that were isolated from the influence of Caesar's Creek, which flushes water from inside Biscayne Bay onto the open shelf. Unidentifiable grains predominated in the sediment constituents, along with calcareous algae and molluskan debris. Shells from 82 genera of Foraminifera were identified in the sediments. Quinqueloculina was the most consistently common genus. Percent mud was the single most influential measured variable on the distribution of both sediment constituents and foraminiferal assemblages. Analysis of bleaching in the foraminifer Amphistegina gibbosa revealed that photo-oxidative stress was chronic at 94% of the sites.

Patterns of FORAM and SEDCON Index values and their similarity to temperature, salinity, and percent mud distributions show that Caesar's Creek is affecting the benthic community in its immediate vicinity by providing flow that limits the accumulation of mud and potentially other anthropogenic stressors. Overall this study suggests that the reefs in this area are marginal for continued reef growth. A more detailed study of water quality through Caesar's Creek should be conducted to determine exactly how it is affecting the reefs in Biscayne National Park.

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