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Relationships between denitrification rates and denitrifier abundance determined by molecular approaches


From 07/2010

Principal Investigator: Hojeong Kang, Gerhard Gebauer
Grant: IRTG 1565 WP II TERRECO - Complex Terrain and Ecological Heterogeneity - Evaluating ecosystem services in production versus water yield and water quality in mountainous landscapes

The denitrification process is of great importance in various environmental issues, because it is a key removal process of nitrogen from water bodies, and its by-product, N2O, is a radiatively active gas of concern with respect to climate change. Denitrification is mostly mediated by facultative anaerobic bacteria under anaerobic conditions. Previous studies have reported key controlling variables for denitrification such as redox potential, carbon availability and nitrate supply. Recently, various molecular approaches have allowed us to better understand abundance and composition of bacteria involved in the process, but not many studies have linked such information to process rates.

In this study, we are measuring denitrification rates, employing an acetylene blocking method along with bacterial analysis for their abundance (real time Q-PCR) and composition (T-RFLP) in various ecosystems. The target genes were nirS and nosZ genes, and ecosystems assessed include constructed wetlands, riparian wetlands, stream sediments and floodplain soils. Denitrification rates appear to be strongly influenced by environmental conditions such as temperature, organic matter content and pH. In contrast, microbial abundance measured by real time Q-PCR have not exhibited substantial variations over seasons. Poor correlations between process rates and microbial abundance suggest that both approaches should be employed complementary to better understand denitrification process. Within TERRECO, we specifically attempt to analyze the composition of bacterial populations and their change in relation to the landscape and ecosystem types of the Haean catchment. We also examine bacterial populations simultaneously with observations of N2O emissions.

last modified 2010-11-03