title: Seasonal variation in denitrification and dissimilatory nitrate reduction to ammonia process rates and corresponding key functional genes along an estuarine nitrate gradient.
abstract: This research investigated spatial-temporal variation in benthic bacterial community structure, rates of denitrification and dissimilatory nitrate reduction to ammonium (DNRA) processes and abundances of corresponding genes and transcripts at three sites-the estuary-head, mid-estuary and the estuary mouth (EM) along the nitrate gradient of the Colne estuary over an annual cycle. Denitrification rates declined down the estuary, while DNRA rates were higher at the estuary head and middle than the EM. In four out of the six 2-monthly time-points, rates of DNRA were greater than denitrification at each site. Abundance of gene markers for nitrate-reduction (nitrate reductase narG and napA), denitrification (nitrite reductase nirS) and DNRA (DNRA nitrite reductase nrfA) declined along the estuary with significant relationships between denitrification and nirS abundance, and DNRA and nrfA abundance. Spatially, rates of denitrification, DNRA and corresponding functional gene abundances decreased along the estuary. However, temporal correlations between rate processes and functional gene and transcript abundances were not observed.
authors.affiliation: Department of Biological Sciences, University of Essex , Colchester, UK ; Department of Animal and Plant Sciences, The University of Sheffield , Sheffield, UK.
authors.forename: Cindy J
authors.initials: CJ
authors.lastname: Smith
authors.affiliation: Department of Biological Sciences, University of Essex , Colchester, UK.
authors.forename: Liang F
authors.initials: LF
authors.lastname: Dong
authors.affiliation: Department of Animal and Plant Sciences, The University of Sheffield , Sheffield, UK.
authors.forename: John
authors.initials: J
authors.lastname: Wilson
authors.affiliation: NERC Life Sciences Mass Spectrometry Facility, Centre for Ecology and Hydrology, Lancaster Environment Centre , Lancaster, UK.
authors.forename: Andrew
authors.initials: A
authors.lastname: Stott
authors.affiliation: Department of Animal and Plant Sciences, The University of Sheffield , Sheffield, UK.
authors.forename: A Mark
authors.initials: AM
authors.lastname: Osborn
authors.affiliation: Department of Biological Sciences, University of Essex , Colchester, UK.
authors.forename: David B
authors.initials: DB
authors.lastname: Nedwell
keywords: (RT)-Q-PCR; denitrification/DNRA; napA; narG; nirS; nrfA