caa a22 4500 60551738X CHVBK 20210128100719.0 cr unu---uuuuu 210128e20151101xx s 000 0 eng 10.1007/s10533-015-0153-9 doi (NATIONALLICENCE)springer-10.1007/s10533-015-0153-9 Direct response of dissolved organic nitrogen to nitrate availability in headwater streams [Elektronische Daten] [Adam Wymore, Bianca Rodríguez-Cardona, William McDowell] Despite decades of research documenting the quantitative significance of dissolved organic nitrogen (DON) across ecosystems, the drivers controlling its production and consumption are not well understood. As an organic nutrient DON may serve as either an energy or nitrogen source. One hypothesized control on DON concentration in streams is nitrate (NO3 −) availability. Synoptic surveys of DON and NO3 −, however, have yielded inconsistent spatial and temporal patterns. Using a nutrient pulse method we experimentally manipulated stream NO3 − and measured the response of both the manipulated solute and ambient concentrations of DON in three New Hampshire headwater streams. This direct experimental addition of NO3 − often altered ambient DON concentrations in situ, with both increases and decreases observed. The overall relationship between NO3 − and DON suggests that DON is primarily used as a nutrient source in these streams, as evidenced by net DON accumulation with added NO3 −. However, strong underlying seasonal patterns in the response to NO3 − addition are also discernable, indicating that the role of DON can switch between serving as a nutrient source to an energy source (as evidenced by net DON reduction with added NO3 −). We also observed differences in the NO3 −—DON relationship (net DON accumulation vs. net DON reduction) in two streams less than five miles apart when experiments were conducted within the same month. Based on these results, we expect the role of DON within ecosystems to vary among watersheds and throughout the growing season, alternating between serving as a nutrient and energy source depending on environmental conditions. With the incorporation of a new field-based method we demonstrate that the ambient DON pool can be manipulated in situ. This approach has the potential for furthering our understanding of DON across ecosystems. Springer International Publishing Switzerland, 2015 Dissolved organic nitrogen nationallicence Nitrate nationallicence Organic matter nationallicence Stream ecosystems nationallicence Nitrogen cycling nationallicence Wymore Adam Department of Natural Resources and the Environment, University of New Hampshire, 114 James Hall, 56 College Road, 03824, Durham, NH, USA aut Rodríguez-Cardona Bianca Department of Natural Resources and the Environment, University of New Hampshire, 114 James Hall, 56 College Road, 03824, Durham, NH, USA aut McDowell William Department of Natural Resources and the Environment, University of New Hampshire, 114 James Hall, 56 College Road, 03824, Durham, NH, USA aut Biogeochemistry Springer International Publishing 126/1-2(2015-11-01), 1-10 0168-2563 126:1-2<1 2015 126 10533 https://doi.org/10.1007/s10533-015-0153-9 text/html Onlinezugriff via DOI BK010053 XK010053 XK010000 Metadata rights reserved Springer special CC-BY-NC licence nationallicence 1 review-article jats NATIONALLICENCE NATIONALLICENCE NL-springer NATIONALLICENCE 856 40 https://doi.org/10.1007/s10533-015-0153-9 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Wymore Adam Department of Natural Resources and the Environment, University of New Hampshire, 114 James Hall, 56 College Road, 03824, Durham, NH, USA aut NATIONALLICENCE 700 1- Rodríguez-Cardona Bianca Department of Natural Resources and the Environment, University of New Hampshire, 114 James Hall, 56 College Road, 03824, Durham, NH, USA aut NATIONALLICENCE 700 1- McDowell William Department of Natural Resources and the Environment, University of New Hampshire, 114 James Hall, 56 College Road, 03824, Durham, NH, USA aut NATIONALLICENCE 773 0- Biogeochemistry Springer International Publishing 126/1-2(2015-11-01), 1-10 0168-2563 126:1-2<1 2015 126 10533