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Denitrification in an Estuarine Headwater Creek within an Agricultural Watershed
Author(s) -
Thompson Suzanne P.,
Piehler Michael F.,
Paerl Hans W.
Publication year - 2000
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2000.00472425002900060026x
Subject(s) - denitrification , environmental science , culvert , surface runoff , hydrology (agriculture) , nitrification , estuary , watershed , nitrogen , ecology , chemistry , geology , biology , geotechnical engineering , organic chemistry , machine learning , computer science
Nonpoint agricultural surface water runoff has been identified as a significant contributor to watershed nitrogen (N) loading. Denitrification is thought to be a substantial sink for N inputs to estuaries. Denitrification rates and inorganic N concentrations were measured in Culvert Creek, NC for a 3‐yr period with an adaptation of the acetylene block technique using saturation kinetic incubations that provided estimated in situ and potential rates. Estimated in situ denitrification and inorganic N concentrations were elevated in portions of Culvert Creek, NC following fertilizer application at adjacent Open Grounds Farm. Statistical correlations indicated that denitrification in Culvert Creek was regulated by inorganic N, paticularly at headwater sites. Regulation was complex at estuarine sites, where dynamic hydrological conditions affected microbial processing of N through coupled nitrification‐denitrification. Potential denitrification rates were often an order of magnitude higher than estimated in situ rates. Potential denitrification showed a similar seasonal‐spatial pattern to that of nitrification at the most estuarine site, with lower rates at the mid‐creek sites where nitrification was inhibited during periods of anoxia. Annual N removal in Culvert Creek was estimated at 1.27% (in situ) or 68.70% (potential rates) of inputs. An estimated 11% of N inputs were removed via the nitrification‐denitrification pathway in Culvert Creek assuming that rates were closely coupled. Mean annual (1995–1997) creek denitrification rates of 2.17 kg N ha −1 yr −1 (in situ) and 90.52 kg N ha −1 yr −1 (potential) were within the range of rates measured in various freshwater wetland systems receiving agricultural drainage. In Culvert Creek, denitrification was a significant mediator of estuarine headwater N cycling.