Controls on Bacterial Activity
My dissertation research focused on microbial ecology in arctic lakes and streams to study the relationship between biodiveristy and ecosystem function. This research was conducted at Toolik Field Station in collaboration with Byron Crump of Horn Point Laboratory (HPL-UMCES) and the Arctic Long-term Ecological Research (ARC-LTER) group. I earned my doctorate at the University of Michigan, in the Department of Ecology and Evolutionary Biology, with George Kling and my dissertation committee members included Byron Crump, Deborah Goldberg, Don Zak, and Paul Dunlap.
My dissertation focused on four controls of bacterial activity and examined their mechanisms and interactions.
- Temperature: can constrain response to available carbon substrates
- Nutrients: limitation can occur, especially under conditions of low temperature or high C:N in available substrate
- Downstream dispersal: water flushes materials and bacteria downslope and downstream, from terrestrial systems into streams and lakes.
- Bacterial community composition: varies across the landscape.
Research questions that I have examined include:
- Spatial and temporal variability in bacterial production and community composition across catchments.
- The interaction between temperature, substrate source, and community composition.
- Interactions of temperature and nutrient limitation on bacterial production and impacts on community composition.
- With-in lake and with-in stream response of bacterial production to rain events.
- Measurement of variation in type of dissolved organic matter in streams over three summer seasons.
- Response of "transient" versus "resident" bacterial communities in situ.
- Importance of mass effects versus species sorting in relation to community composition and productivity.
Community composition was analyzed using denaturant gradient gel electrophoresis (DGGE) in collaboration with Byron Crump at the University of Maryland Center for Environmental Science at the Horn Point Laboratory.
Funding for my research was provided by:
- EPA STAR Fellowship (2007- 2009)
- Edwin H. Edwards Fellowship (2006-2007)
- Helen Brower Olsen Endowed Fellowship (2004-2006)
- Rackham Discretionary Funds (2003-2004)
- Department of Ecology and Evolutionary Biology Block Grant (2002-2003, 2007-2008)
- Office of Polar Programs (2002-2006)
- NSF Arctic LTER
Top photos: Jen Kostrzewski sampling Toolik Lake, Heather Adams and Alex Mettler at Lake I-8, and Jessica Spence setting up transplant experiments at the Lake I-8 inlet.
Bottom photo: Lake I-8, upstream from Toolik Lake, as seen from helicopter.