Graduation Year


Document Type




Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Biology (Cell Biology, Microbiology, Molecular Biology)

Major Professor

James R. Garey, Ph.D.

Committee Member

Jason D. Gulley, Ph.D.

Committee Member

Bogdan P. Onac, Ph.D.

Committee Member

Prahathees J. Eswara, Ph.D.


Aquifer, Cave, Coastal Landscape, Molecular Ecology, Seawater Intrusion, Spring


Sulphur Springs is an artesian spring and part of the limestone karst topography of metropolitan Tampa, Florida, USA. Underlying this spring is an extensive cave system that hosts saltwater vents and conspicuous microbial biofilm communities. For decades, water from Sulphur Springs has been extracted and used to supplement public water supply and dry season flows in the Hillsborough River Estuary. This dissertation describes research conducted at Sulphur Springs to determine the impacts of urban land use on the underlying cave and downstream estuary ecosystems, and presents the use of this system as a model to fill certain ecological knowledge gaps. Techniques from a wide array of disciplines were used to address these questions, such as molecular biology, stable isotope geochemistry, hydrogeology, and multivariate statistics. The introduction provides a brief background about the major anthropogenic changes faced by groundwater-dependent ecosystems. The first chapter presents evidence for a conceptual model that explains how seawater intrusion accelerated by groundwater extraction has occurred at Sulphur Springs. The second chapter addresses knowledge gaps in the concepts behind the use of microbial indicators in groundwater, and applies the microbial indicator tool to inform management strategies at Sulphur Springs. The third chapter demonstrates how the use of extracted groundwater to supplement riverine discharge impacts carbon fluxes in estuaries, and how groundwater extraction from karst springs can change underlying cave ecosystems. The concluding remarks propose future directions for ecological research in karst subterranean estuaries and coastal landscapes. Overall, this dissertation demonstrates how anthropogenic activity can modify coastal groundwater and estuary ecosystems, and emphasizes how local management strategies are causing fundamental ecological change at Sulphur Springs.