caa a22 4500 467885974 CHVBK 20180406152734.0 cr unu---uuuuu 170328e20060801xx s 000 0 eng 10.1007/s10021-006-0005-5 doi (NATIONALLICENCE)springer-10.1007/s10021-006-0005-5 Coupling Nutrient Uptake and Energy Flow in Headwater Streams [Elektronische Daten] [C. Fellows, H. Valett, C. Dahm, P. Mulholland, S. Thomas] Nutrient cycling and energy flow in ecosystems are tightly linked through the metabolic processes of organisms. Greater uptake of inorganic nutrients is expected to be associated with higher rates of metabolism [gross primary production (GPP) and respiration (R)], due to assimilatory demand of both autotrophs and heterotrophs. However, relationships between uptake and metabolism should vary with the relative contribution of autochthonous and allochthonous sources of organic matter. To investigate the relationship between metabolism and nutrient uptake, we used whole-stream and benthic chamber methods to measure rates of nitrate-nitrogen (NO3-N) uptake and metabolism in four headwater streams chosen to span a range of light availability and therefore differing rates of GPP and contributions of autochthonous carbon. We coupled whole-stream metabolism with measures of NO3-N uptake conducted repeatedly over the same stream reach during both day and night, as well as incubating benthic sediments under both light and dark conditions. NO3-N uptake was generally greater in daylight compared to dark conditions, and although day-night differences in whole-stream uptake were not significant, light-dark differences in benthic chambers were significant at three of the four sites. Estimates of N demand indicated that assimilation by photoautotrophs could account for the majority of NO3-N uptake at the two sites with relatively open canopies. Contrary to expectations, photoautotrophs contributed substantially to NO3-N uptake even at the two closed-canopy sites, which had low values of GPP/R and relied heavily on allochthonous carbon to fuel R. Springer Science+Business Media, Inc., 2006 metabolism nationallicence nitrogen nationallicence carbon nationallicence primary production nationallicence respiration nationallicence autotroph nationallicence heterotroph nationallicence autochthonous nationallicence allochthonous nationallicence Fellows C. Centre for Riverine Landscapes, Faculty of Environmental Sciences, Griffith University, 4111, Nathan, Queensland, Australia aut Valett H. Department of Biology, Virginia Polytechnic Institute and State University, 24061, Blacksburg, Virginia, USA aut Dahm C. Department of Biology, University of New Mexico, 87131, Albuquerque, New Mexico, USA aut Mulholland P. Environmental Sciences Division, Oak Ridge National Laboratories, 37831-6036, Oak Ridge, Tennessee, USA aut Thomas S. Department of Ecology and Evolutionary Biology, Cornell University, Corson Hall, 14853-2701, Ithaca, New York, USA aut Ecosystems Springer-Verlag; www.springer-ny.com 9/5(2006-08-01), 788-804 1432-9840 9:5<788 2006 9 10021 https://doi.org/10.1007/s10021-006-0005-5 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s10021-006-0005-5 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Fellows C. Centre for Riverine Landscapes, Faculty of Environmental Sciences, Griffith University, 4111, Nathan, Queensland, Australia aut NATIONALLICENCE 700 1- Valett H. Department of Biology, Virginia Polytechnic Institute and State University, 24061, Blacksburg, Virginia, USA aut NATIONALLICENCE 700 1- Dahm C. Department of Biology, University of New Mexico, 87131, Albuquerque, New Mexico, USA aut NATIONALLICENCE 700 1- Mulholland P. Environmental Sciences Division, Oak Ridge National Laboratories, 37831-6036, Oak Ridge, Tennessee, USA aut NATIONALLICENCE 700 1- Thomas S. Department of Ecology and Evolutionary Biology, Cornell University, Corson Hall, 14853-2701, Ithaca, New York, USA aut NATIONALLICENCE 773 0- Ecosystems Springer-Verlag; www.springer-ny.com 9/5(2006-08-01), 788-804 1432-9840 9:5<788 2006 9 10021 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer