W. Bane Schill¹, James R. Murray² and G. Lynn Wingard^2
1USGS-Leetown Science Center, Kearneysville, WV, USA
²USGS-National Center, Reston, VA USA

Bacteria are ubiquitous inhabitants of all sorts of environments including fresh and salt waters, thermal vents, arctic snow, acidic mine drainage, petroleum deposits, soils, and sediments. Large shifts in microbial populations can be triggered by subtle environmental cues, but once begun, these shifts may themselves cause dramatic ecosystem changes. This is because microbes are responsible for many geochemical processes including metal and sulfur oxidation and reduction, nitrification and denitrification, fermentation, and methane production. Recent studies have demonstrated that bacterial DNA can be preserved for long periods of time when protected from nuclease digestion by being bound to sediments or preserved in cellular membrane envelopes. We have investigated the potential of using microbial assemblage shifts associated with core strata to determine historic water conditions by using molecular methods.

Bulk bacterial DNA was isolated from sediment core fractions and subjected to polymerase chain reaction (PCR) using oligonucleotide primers that direct the amplification of the DNA of bacterial groups of interest. One such group is the Cyanobacteria (blue-green algae). Their typical association with surface layers and their sensitivity to water quality make them a potentially useful “canary” for historic conditions if their DNA is detectable in down-core strata. We report that we have, in fact, detected preserved DNA reflecting the presence of these (and other) bacteria in core samples down to 110 cm below the surface. Moreover, we have observed that species composition varies markedly with events reflected in core lithology.

We have also conducted microcosm experiments to determine the effects of parameters including salinity and temperature change on bacterial species composition. Just as is the case with macrofauna, some bacterial species were found to tolerate a wide range of conditions, while others were found to be more sensitive to change. Although these studies are in their infancy, the goal is to identify groups of bacterial species that prefer various conditions and to further develop and streamline analytical methods to quantify the presence of these species in core strata thus characterizing the water conditions at the time the sediment was deposited.

Contact Information: W. Bane Schill, USGS-Leetown Science Center, 11649 Leetown Road, Kearneysville, WV 25430 USA, Phone: 304-724-4438, Fax: 3047244435, Email: wschill@usgs.gov

(This abstract is from the 2006 Greater Everglades Ecosystem Restoration Conference.)

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