Feburary 2015 Meeting

Monday, February 9, 2015
6:00 - 7:30 pm

Pellissippi State Technical Community College
10915 Hardin Valley Road, Knoxville
J.L. Goins Administration Building, Cafeteria Annex


The Dark Side of the Carbon Cycle:
Organic Matter Transformations in a Karst Aquifer

Terri Brown

University of Tennessee
Department of Earth and Planetary Sciences
Knoxville, Tennessee


Freshwater ecosystem functions at the land-groundwater interface (ie., recharge and discharge areas) are controlled by diverse microbial communities that transform and cycle elements and nutrients through their metabolic activities. Particulate, dissolved, and colloidal organic matter (OM) constitute the largest reservoir of organic carbon in freshwater environments; however, quantification and modelling of OM fluxes are complicated by myriad environmental factors that affect its composition and bioavailability, including watershed characteristics, land use, and climate. Mechanistic uncertainties about the mean residence times of OM in soils and aquatic systems exist, in part, due to an emerging understanding of isotopic signatures in OM, the lack of standard OM characterization protocols, and continued use of outdated terminologies that create barriers to cross-disciplinary collaboration. We investigated OM transformations and degradation dynamics in a Kentucky cave system over several seasons in order to test hypotheses about OM recalcitrance, composition, and microbially-mediated processes in the subsurface. In this talk, I will describe the aspects of dye tracing, hydrochemistry, OM isolation, spectroscopic characterization, and microbial community profiling employed during my research, as well as some unexpected findings that reveal the important role that cave systems and karst aquifers play in regulating nutrient loads in watersheds.


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