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Environmental drivers of denitrification rates and denitrifying gene abundances in channels and riparian areas
Author(s) -
Tomasek Abigail,
Kozarek Jessica L.,
Hondzo Miki,
Lurndahl Nicole,
Sadowsky Michael J.,
Wang Ping,
Staley Christopher
Publication year - 2017
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1002/2016wr019566
Subject(s) - denitrification , denitrifying bacteria , riparian zone , environmental science , abundance (ecology) , hydrology (agriculture) , ecology , environmental chemistry , nitrogen , biology , chemistry , habitat , geology , geotechnical engineering , organic chemistry
Intensive agriculture in the Midwestern United States contributes to excess nitrogen in surface water and groundwater, negatively affecting human health and aquatic ecosystems. Complete denitrification removes reactive nitrogen from aquatic environments and releases inert dinitrogen gas. We examined denitrification rates and the abundances of denitrifying genes and total bacteria at three sites in an agricultural watershed and in an experimental stream in Minnesota. Sampling was conducted along transects with a gradient from always inundated (in‐channel), to periodically inundated, to noninundated conditions to determine how denitrification rates and gene abundances varied from channels to riparian areas with different inundation histories. Results indicate a coupling between environmental parameters, gene abundances, and denitrification rates at the in‐channel locations, and limited to no coupling at the periodically inundated and noninundated locations, respectively. Nutrient‐amended potential denitrification rates for the in‐channel locations were significantly correlated ( α = 0.05) with five of six measured denitrifying gene abundances, whereas the periodically inundated and noninundated locations were each only significantly correlated with the abundance of one denitrifying gene. These results suggest that DNA‐based analysis of denitrifying gene abundances alone cannot predict functional responses (denitrification potential), especially in studies with varying hydrologic regimes. A scaling analysis was performed to develop a predictive functional relationship relating environmental parameters to denitrification rates for in‐channel locations. This method could be applied to other geographic and climatic regions to predict the occurrence of denitrification hot spots.