Wednesday, May 28, 2008 - 9:15 AM
374

Habitat stability and benthic bacterial communities on rocks and sediments in a small temperate stream

Louis A. Kaplan, Stroud Water Research Center, 970 Spencer Road, Avondale, PA 19311 and Karen R. Hogan, Department of Biology, University of Pennsylvania, Hamilton Walk, Philadelphia, PA 19104.

Biological, chemical, and physical factors interact to influence the structure and productivity of benthic bacterial communities in streams.  We measured bacterial biomass with direct microscopy, bacterial production with radiolabeled thymidine, and bacterial community composition with molecular fingerprinting.  Consistent differences throughout the year were observed in the structure and function of bacterial communities attached to rocks in riffles and those attached to sediments in runs of a 3rd order piedmont stream.  A February storm reduced the biomass and productivity of bacteria attached to sediments by 48% and 90%, respectively, while reducing the biomass of bacteria attached to rocks by 21% and increasing bacterial productivity by 22%.  An August storm had similar effects, reducing bacterial biomass and production associated with sediments by 32% and 52% respectively, while reducing the biomass of bacteria attached to rocks by 20% and increasing bacterial productivity by 30%.  Molecular fingerprints of community composition assessed from composite samples of streambed sediments collected under baseflow conditions and following storms revealed a stable “climax community” that was altered by storms, but eventually returned to its original composition.  These investigations contribute to our understanding of microbial biogeography and the importance of habitat stability to the microbial ecology within a single stream.


Web Page: molecular fingerprint, bacterial production

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