HR: 16:15h
AN: B24A-04 INVITED     [Abstracts]
TI: Upslope dissolved organic matter controls bacterial activity through shifts in community composition
AU: * Judd, K E
EM: juddk@ecostudies.org
AF: Institute of Ecosystem Studies, 65 Sharon Turnpike, P.O. Box AB, Millbrook, NY 12545 United States
AU: Crump, B C
EM: bcrump@hpl.umces.edu
AF: Center for Environmental Science University of Maryland, 2020 Horns Point Rd., Cambridge, MD 21613 United States
AU: Kling, G W
EM: gwk@umich.edu
AF: Department of Ecology and Evolutionary Biology University of Michigan, 830 North Univeristy Ave., Ann Arbor, MI 48109 United States
AB: Water moving through heterogeneous catchments supplies distinct down-slope bacterial communities with dissolved organic matter (DOM) of distinct chemical composition. Yet interactions between DOM sources and bacterial communities are not well understood at the catchment level. To investigate how upslope DOM influences bacterial activity and community composition, we used mesocosm experiments to manipulate DOM source from along a toposequence fed to down-slope bacteria. We measured bacterial production (BP) throughout the experiment and characterized DOM chemistry and bacterial community composition (using denaturing gradient gel electrophoresis of 16S rRNA) at the beginning and end of the experiment. Compared to lake controls, lake bacteria fed soil water DOM had higher integrated BP (420%) and DOC-specific BP (532%). Addition of upslope DOM to lake bacteria shifted community composition in the direction of the community from which the DOM originated relative to controls. Results demonstrated a surprisingly complete functional redundancy among natural soil, stream, and lake water communities, and showed that DOM controlled the level of bacterial activity, but only through alterations in bacterial community composition. We suggest that water flow through catchments will govern these interactions by influencing contact time between DOM and bacterial communities.
DE: 1615 Biogeochemical processes (4805)
DE: 1832 Groundwater transport
DE: 4803 Bacteria
SC: Biogeosciences [B]
MN: 2005 Joint Assembly