LIMESTONE DISSOLUTION IN A COASTAL KARST SYSTEM

Calcite dissolution is influenced by a combination of chemical, mechanical, and biological factors. Dissolution is primarily controlled in groundwater by environmental factors such as pH, flow rates, and calcium carbonate saturation levels. Microbes that form biofilms on limestone surfaces have been shown to contribute significantly to dissolution rates through the production of acidic metabolic byproducts. Identifying the biological factors affecting limestone dissolution is important for predicting rates of conduit wall retreat and sinkhole formation. Previous studies that used in situ experiments, which allow for environmental factors that cannot be replicated in the lab, have focused on microbes in sulfidic or freshwater environments. Microbial communities in coastal, saline springs are shaped by marine intrusion and tidal influence and have yet to be studied with respect to microbe-driven calcite dissolution. In this study, an in situ experiment in a brackish, karstic spring on Florida’s Gulf Coast was used to measure rates of limestone dissolution under varying levels of flow. Results showed a faster rate of dissolution for microbe-colonized limestone than for sterile limestone and higher dissolution rates were found for treatments with higher flow rates. The microbial communities of the spring system are currently being investigated using quantitative polymerase chain reaction and length heterogeneity PCR to compare the microbial community structures of the attached and planktonic communities.