PERSISTENT COLIFORM CONTAMINATION IN LECHUGUILLA CAVE POOLS
Despite designated trails, limited access, water pitchers, and other low-impact caving techniques, coliforms, a bacterial indicator of fecal contamination, are found in the drinking-water pools of Lechuguilla Cave, Carlsbad Caverns National Park, New Mexico. Researchers, concerned cavers, and Carlsbad Caverns National Park Service staff have restored contaminated areas; nevertheless, coliforms persist over time. Investigation of the problem showed that water-siphoning tubing support strong biofilm growth in the same pools in which coliforms are present, suggesting that the biofilm is a factor in coliform persistence. We took a three-pronged approach in exploring this problem: 1) Identification of coliform presence and persistence using +/- coliform indicator quantification tests, 2) Culturing of coliforms in the presence and absence of biofilm to test whether the biofilm enhances coliform growth, and 3) Assessment of biofilm growth on tubing by suspending tubing of varying chemical compositions in cave water. Results indicated that coliform levels exceed those set by the Environmental Protection Agency for drinking-water. Additionally, coliform populations increased in the presence of the biofilm. VWR Tygon showed the heaviest biofilm development while silicone and Teflon tubing did not support any visible biofilm growth in lab experiments. Remediation efforts and management recommendations for the current problem are discussed.