PARENT SESSION
Poster Session #5: Disturbance Ecology I.
Monday, August 5. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC

Impacts of chemical disturbance on the diversity of subsurface microbial communities.

O'CONNELL, SEAN^*,1, Lehman, R. Michael², Watwood, Mary³, Colwell, Frederick², ¹ Department of Biological Sciences, Cullowhee, NC² Geomicrobiology Group, Idaho Falls, ID³ Department of Biology, Pocatello, ID

ABSTRACT- Chemical contamination of subsurface ecosystems is widespread and often has negative effects such as decreased drinking water quality. Assessment of microbial community diversity in subsurface environments has recently received significant attention, but impacts of contaminants on microorganisms are largely unknown. Microcosm experiments were conducted to assess the effects of trichloroethylene (TCE), on microbial diversity in groundwater. Serum vials containing groundwater and 4E+04 prokaryotic cells/ml were exposed to TCE ranging from 0 to 500ppm. Two distinct microcosms were established with different initial species richnesses then examined to determine final species richness and evenness. Methods included spread plating to assess heterotrophic diversity and PCR amplification of 16S rDNA genes followed by denaturing gradient gel electrophoresis (DGGE). Changes in diversity parameters, based on the Shannon-Wiener index, corresponded to TCE levels in the exposed microcosms. For microcosms with low initial species richness, H' values were 1.93, 1.28, 1.50, and 0.69 for unexposed, 1ppm, 100ppm, and 500ppm TCE, respectively (26 species from 704 total colonies observed). For microcosms with high initial species richness, H' values were 2.44, 2.66, 2.51, 2.48, and 1.89 for untreated, 1ppm, 100ppm, 250ppm, and 500ppm TCE, respectively (76 species from 3,247 total colonies observed); diversity assessment based on DGGE analysis gave similar results, with H' values of 2.14, 2.30, 2.58, 2.38, and 1.88 for the same treatments, respectively (18 total species observed as DNA bands). Microcosms with higher initial species richness appeared less sensitive to TCE impacts, except for the highest concentration treatment. However, principal components analyses of molecular and culture-based diversity data showed distinct patterns based solely on TCE treatment; thus the raw diversity data alone could distinguish these microbial communities. Diversity patterns may be useful in tracking environmental impact and may ultimately serve as signatures of ecosystem recovery. The wealth of information from such microbial studies can be used in conjunction with multivariate analysis to distinguish levels of chemical disturbance and may be useful for developing models relevant to higher trophic levels.

KEY WORDS: Bacteria, Community, Diversity, Disturbance