AUTHOR=Smith Cindy J. , Dong Liang F. , Wilson John , Stott Andrew , Osborn A. Mark , Nedwell David B. 

TITLE=Seasonal variation in denitrification and dissimilatory nitrate reduction to ammonia process rates and corresponding key functional genes along an estuarine nitrate gradient

JOURNAL=Frontiers in Microbiology

VOLUME=6

YEAR=2015

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2015.00542

DOI=10.3389/fmicb.2015.00542

ISSN=1664-302X

ABSTRACT=<p>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 <italic>narG</italic> and <italic>napA</italic>), denitrification (nitrite reductase <italic>nirS</italic>) and DNRA (DNRA nitrite reductase <italic>nrfA</italic>) declined along the estuary with significant relationships between denitrification and <italic>nirS</italic> abundance, and DNRA and <italic>nrfA</italic> 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.</p>