Drivers of nitrogen transfer in stream food webs across continents

Authors

B. C. Norman, Michigan State UniversityFollow
M. R. Whiles, Southern Illinois University
S. M. Collins, University of Wisconsin-Madison
A. S. Flecker, Cornell University
S. K. Hamilton, Michigan State University
S. L. Johnson, USDA Forest Service
E. J. Rosi-Marshall, Cary Institute of Ecosystem Studies
L. R. Ashkenas, Oregon State University
W. B. Bowden, University of Vermont
C. L. Crenshaw, University of New Mexico
T. Crowl, Florida International University
W. K. Dodds, Kansas State University
R. O. Hall, University of Wyoming
R. El-Sabaawi, University of Victoria
N. A. Griffiths, Climate Change Science Institute & Environmental Sciences Division
E. Marti, Centre d’Estudis Avançats de Blanes
W. H. McDowell, University of New Hampshire
S. D. Peterson, Murray State University
H. M. Rantala, Division of Fish & Wildlife
T. Riis, Aarhus University
K. S. Simon, University of AucklandFollow
J. L. Tank, University of Notre Dame
S. A. Thomas, University of Nebraska-LincolnFollow
D. von Schiller, University of the Basque Country
J. R. Webster, Virginia Polytechnic Institute and State University

Document Type

Article

Date of this Version

2017

Citation

doi: 10.1002/ecy.2009.

Comments

U.S. government work.

Abstract

Studies of trophic-level material and energy transfers are central to ecology. The use of isotopic tracers has now made it possible to measure trophic transfer efficiencies of important nutrients and to better understand how these materials move through food webs. We analyzed data from thirteen ¹⁵N-ammonium tracer addition experiments to quantify N transfer from basal resources to animals in headwater streams with varying physical, chemical, and biological features. N transfer efficiencies from primary uptake compartments (PUCs; heterotrophic microorganisms and primary producers) to primary consumers was lower (mean: 11.5%, range:100%). Total N transferred (as a rate) was greater in streams with open compared to closed canopies and overall N transfer efficiency generally followed a similar pattern, although was not statistically significant. We used principal component analysis to condense a suite of site characteristics into two environmental components. Total N uptake rates among trophic levels were best predicted by the component that was correlated with latitude, DIN:SRP, GPP:ER, and % canopy cover. N transfer efficiency did not respond consistently to environmental variables. Our results suggest that canopy cover influences N movement through stream food webs because light availability and primary production facilitate N transfer to higher trophic levels.