Year Established: 2016 Start Date: 2016-03-01 End Date: 2017-02-28
Total Federal Funds: $22,931 Total Non-Federal Funds: $46,954
Principal Investigators: Matthew Covington, Kristen Gibson
Abstract: An estimated 20% of the world's population depends on groundwater obtained from karst aquifers. Within karst settings, groundwater is routed through conduit systems that form through the gradual dissolution of the rock. Perhaps the most serious challenge in karst is its extreme vulnerability to contamination, since contaminants such as excess nutrients, heavy metals, and human pathogens can move quickly through the ground in unpredictable directions with little filtration. Unfortunately, the dynamics of contaminants within karst aquifers remain relatively poorly understood, particularly contaminants that can sorb onto aquifer surfaces or travel attached to sediment particles, including fecal indicator bacteria (FIB) such as Escherichia coli and human pathogens including bacteria and viruses. Northern Arkansas is underlain largely by carbonate bedrock, with relatively well-developed karst flow systems. Much of this region is rapidly urbanizing, leading to a variety of potential threats to groundwater, including increased, and redirected, runoff and the potential introduction of contaminants into the subsurface via septic systems, effluent wastewater discharge, and agricultural runoff. The proposed study will use genetic fingerprinting of bacteria at Blowing Spring Cave (BSC), a site with known FIB contamination, to identify potential sources and expand understanding of the dynamics of FIB within karst systems. The objectives of the proposed study are to: 1) explore structure, diversity, and temporal variability of microbial communities at BSC and Little Sugar Creek, a nearby surface stream fed by BSC; 2) differentiate allochthonous bacteria from land surface runoff and autochthonous bacteria in the sediments and water of the endokarst; 3) determine impact of sediment movement from karst springs to LSC through comparison of microbial communities; 4) delineate the recharge area of BSC and constrain potential sources of E. coli. Our overarching question is whether microbial communities within BSC evolve seasonally, particularly with varying flow conditions. We specifically hypothesize that sediments serve as the primary reservoir of these microbial communities, and that flood events act to inoculate the sediment with fresh communities of bacteria. During post-flood periods, community structure evolves as a function of survival time within the sediment environment. By characterizing bacterial community dynamics in cave sediments and water, we may be better able to understand the impact of sediments on the bacterial community of LSC which is fed by BSC and many other similar karst springs.