| Nitrate (NO3-) uptake and denitrification in small headwater streams can have significant implications for downstream water quality. I measured seasonal NO3- uptake and longitudinal patterns in potential sediment denitrification in a New Hampshire agriculturally influenced stream during 2009. NO3- uptake was measured through short-term NO3- enrichments and potential denitrification was measured using the Chloramphenicol-amended acetylene-inhibition method. NO3 - was taken up in autumn but not in spring or summer. In autumn, on average 87% of the daily NO3- load was taken up and a maximum of 4% was removed via denitrification. Results suggest that, in this stream, carbon availability from leaf fall drives NO3 - uptake primarily via heterotrophic assimilation. This study helps to better characterize controls on NO3- uptake and denitrification in New England, where few such studies have been conducted on agricultural streams, and where seasons are pronounced. |
