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Applied and Environmental Microbiology, December 2008, p. 7585-7595, Vol. 74, No. 24
0099-2240/08/$08.00+0     doi:10.1128/AEM.01221-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Microbial Community Composition and Denitrifying Enzyme Activities in Salt Marsh Sediments{triangledown}

Yiping Cao,1,{dagger} Peter G. Green,2 and Patricia A. Holden1*

Donald Bren School of Environmental Science and Management, University of California, Santa Barbara, California 93106-5131,1 Department of Civil and Environmental Engineering, University of California, Davis, California 956162

Received 2 June 2008/ Accepted 18 September 2008

Denitrifying microbial communities and denitrification in salt marsh sediments may be affected by many factors, including environmental conditions, nutrient availability, and levels of pollutants. The objective of this study was to examine how microbial community composition and denitrification enzyme activities (DEA) at a California salt marsh with high nutrient loading vary with such factors. Sediments were sampled from three elevations, each with different inundation and vegetation patterns, across 12 stations representing various salinity and nutrient conditions. Analyses included determination of cell abundance, total and denitrifier community compositions (by terminal restriction fragment length polymorphism), DEA, nutrients, and eluted metals. Total bacterial (16S rRNA) and denitrifier (nirS) community compositions and DEA were analyzed for their relationships to environmental variables and metal concentrations via multivariate direct gradient and regression analyses, respectively. Community composition and DEA were highly variable within the dynamic salt marsh system, but each was strongly affected by elevation (i.e., degree of inundation) and carbon content as well as by selected metals. Carbon content was highly related to elevation, and the relationships between DEA and carbon content were found to be elevation specific when evaluated across the entire marsh. There were also lateral gradients in the marsh, as evidenced by an even stronger association between community composition and elevation for a marsh subsystem. Lastly, though correlated with similar environmental factors and selected metals, denitrifier community composition and function appeared uncoupled in the marsh.

* Corresponding author. Mailing address: Donald Bren School of Environmental Science and Management, Mail Code 5131, University of California, Santa Barbara, CA 93106-5131. Phone: (805) 893-3195. Fax: (805) 893-7612. E-mail: holden{at}bren.ucsb.edu

{triangledown} Published ahead of print on 31 October 2008.

{dagger} Present address: Southern California Coastal Water Research Project, 3535 Harbor Blvd., Suite 110, Costa Mesa, CA 92626.

Applied and Environmental Microbiology, December 2008, p. 7585-7595, Vol. 74, No. 24
0099-2240/08/$08.00+0     doi:10.1128/AEM.01221-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.





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