Biocomplexity
of Aquatic Microbial Systems:
Relating Diversity of
Microorganisms to Ecosystem Function
Transect of Biocomplexity Stations
Microbial biogeochemical cycling of the elements regulates a dynamic environment in which cycles are linked through the physiology of microorganisms.
- Some understanding of element cycling has been gained through
- physical and chemical measurements
- modeling of the net transformations
- However, these approaches necessarily rely on gross simplifications about the role and regulation of the various functional groups of microorganisms (called guilds) involved.
Recent advances in molecular microbial ecology have shown the microbial world to contain immense diversity and complexity at every level:
- redundancy and duplication of functional genes within a single organism
- molecular diversity among functional genes that encode the same process in different organisms
- large genetic diversity among different organisms apparently engaged in the same biogeochemical function within single communities
- great variability in the species composition of different communities that apparently perform equally well.
The goal of this project is to investigate the functional relationship between complexity in microbial communities and the physical/chemical environment.
THE CHESAPEAKE BAY STUDY, 2000-2005
- State of the art molecular ecological techniques, along with a full suite of ecosystem process measurements, will be employed, along a transect that spans the eutrophic – oligotrophic gradient from the inland waters of the Chesapeake Bay out to the Sargasso Sea.
- Experiments and functional gene studies will focus on key transformations in the carbon and nitrogen cycles (C fixation, N fixation, nitrification, denitrification, urea assimilation).
- The diversity of guilds will be interpreted in terms of ecosystem function, assessed using geochemical data and tracer experiments.
- In addition to field studies designed to investigate and dissect the natural system, we will also perform perturbation experiments using mesocosms.
The goals of these experiments are:
- to determine how microbial species diversity affects the major energy and nutrient flows within ecosystems
- to assess the degree of stability or instability associated with changes in redundancy within guilds of microorganisms responsible for major nitrogen and carbon pathways.
| Mesocosms
were filled with water from Chesapeake Bay and monitored for changes in
nitrogen under varying conditions; June 2004, Horn Point. Mary Voytek
and Julie Kirshtein filtering mesocosm samples
Photos by
Kris Baker
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Chief scientist Jeff Alexander on Chesapeake Bay cruise Collaborators
Jackie Collier and Bess Ward filtering water
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CTD
rosette
deployment from the
Rv Henlopen, Chesapeake Bay
Sunset on Chesapeake
Bay from the
fantail of the RV Henlopen
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photos
by Julie Kirshtein
Publications
Bess B. Ward, Damien Eveillard, Julie D. Kirshtein, Joshua D. Nelson, Mary A. Voytek and George A. Jackson, 2007. Ammonia-oxidizing bacterial community composition in estuarine and oceanic environments assessed using a functional gene microarray. Enivorn. Microbiol. (pdf)
Principal Investigators in Partnership
Mary
Voytek - US Geological Survey
Jackie Collier - Rensselelaer
Polytechnic Institute
Patricia Glibert - University of Maryland
George Jackson - Texas A&M University
Todd Kana - University of Maryland
Bess Ward - Princeton University
Jon Zehr - University of California
