Graduation Year

2015

Document Type

Thesis

Degree

M.S.

Degree Name

Master of Science (M.S.)

Degree Granting Department

Biology (Cell Biology, Microbiology, Molecular Biology)

Major Professor

James R. Garey, Ph.D.

Committee Member

Bogdan Onac, Ph.D.

Committee Member

Kathleen Scott, Ph.D.

Keywords

Karst, Biochemistry, Carbonate

Abstract

Limestone dissolution in karst environments is likely due to geochemistry of the water, the actions of microbial communities, and the effect of water flow. We explored the rate of limestone dissolution and will examine here the microbial communities associated with the limestone. A conduit within the brackish cave, Double Keyhole Spring, on the coast of central west Florida was the site of the experiment. PVC pipes (5cm x 16cm) were filled with crushed limestone that was screened to a 1.9cm – 2.54cm size range. There were three treatments (5 replicates each): Control - sealed autoclaved controls with limestone and conduit water; Low Flow – sealed at one end, with a screen on the other so water contacts the limestone but cannot flow through; High Flow – screen mesh at both ends to allow the flow of conduit water over the limestone in the tube. After 9 months, the samples were retrieved. The Controls showed a loss of 0.33% ± 0.10, Low Flow samples showed a loss of 1.63% ± 0.71, and High Flow samples lost 2.28% ±0.29. Other studies in freshwater conditions found an average mass loss of 2.25% over the same time period under conditions similar to the High Flow sample in this experiment. Q-PCR and LH-PCR were used to estimate microbial density and species richness. The microbial community growing on the limestone samples were found to be significantly different from sediment or water column samples in both diversity and richness. The conclusion of this study is that the archaeal community growing on the limestone is the main biological driver of limestone dissolution in Double Keyhole Spring.

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