Hydrologie and biotic influences on nitrate removal in a subtropical spring-fed river
dc.contributor.author | Heffernan, JB | |
dc.contributor.author | Cohen, MJ | |
dc.contributor.author | Frazer, TK | |
dc.contributor.author | Thomas, RG | |
dc.contributor.author | Rayfield, TJ | |
dc.contributor.author | Gulley, J | |
dc.contributor.author | Martin, JB | |
dc.contributor.author | Delfmo, JJ | |
dc.contributor.author | Graham, WD | |
dc.date.accessioned | 2014-02-06T18:38:50Z | |
dc.date.issued | 2010-01-01 | |
dc.description.abstract | We use a long-term chemical and hydrologic record in combination with longitudinal sampling and highfrequency nitrate (NO3-) measurements from in situ sensors to describe temporal and spatial patterns of nitrogen (N) inputs and removal in the spring-fed Ichetucknee River (Columbia County, Florida) and to determine the hydrological, geomorphic, and biological factors that influence those dynamics. Over a 20-yr period of record, NO 3-N removal averaged 118 kg N d-1 (0.77 g N m-2 d-1 ) over the upper 5 km of the Ichetucknee River. Three independent estimates of gross autotrophic N assimilation (from gross primary production, diel NO3- variation, and standing biomass) agreed closely but accounted for less than 20% of observed N removal. Longitudinal surveys indicate negligible or negative dissolved organic nitrogen and ammonium (NH4+) production, suggesting that denitrification is the predominant mechanism of N removal in this river. A positive relationship between discharge and the magnitude of NO3-N removal shows that interactions with the surrounding floodplain exert considerable influence at high flows, and longitudinal NO3- patterns indicate that N removal may be influenced by channel morphology. These results suggest a greater role for dissimilatory processes and hydrologic connectivity with hyporheic and floodplain sediments than has been previously recognized in highly productive spring-fed rivers of north Florida. While hydrologic variation is the primary determinant of variation in NO 3- removal within the Ichetucknee River, comparison across systems indicates that biotic characteristics can cause significant deviation from predictions based on purely physical models of relationships between river size and N removal. © 2010 by the American Society of Limnology and Oceanography, Inc. | |
dc.identifier.issn | 0024-3590 | |
dc.identifier.uri | ||
dc.publisher | Wiley | |
dc.relation.ispartof | Limnology and Oceanography | |
dc.title | Hydrologie and biotic influences on nitrate removal in a subtropical spring-fed river | |
dc.type | Journal article | |
duke.contributor.orcid | Heffernan, JB|0000-0001-7641-9949 | |
pubs.begin-page | 249 | |
pubs.end-page | 263 | |
pubs.issue | 1 | |
pubs.organisational-group | Duke | |
pubs.organisational-group | Environmental Sciences and Policy | |
pubs.organisational-group | Nicholas School of the Environment | |
pubs.publication-status | Published | |
pubs.volume | 55 |
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