Abstract


NITROGEN FIXATION AMPLIFIES THE TEMPERATURE-DEPENDENCE OF PRIMARY PRODUCTION IN STREAMS

Variation in resource supply can cause large divergence between observed and expected temperature dependencies of metabolic processes (e.g., photosynthesis and respiration); yet, few studies have assessed the effects of temperature-nutrient interactions on metabolic processes, including cases where the supply of limiting nutrients exhibits temperature-dependence. We investigated the responses of GPP, R, and N2-fixation to warming (thermal treatments = 3, 6, 11, 16, 21, and 28 °C) during biofilm community development in a streamside channel experiment. GPP, R, AFDM, and N2-fixation scaled positively with temperature, and GPP exhibited a 500x increase across the temperature gradient. N2-fixation displayed an activation energy of 1.84 eV - a value similar to that reported for the nitrogenase reaction. In contrast, GPP and R had activation energies (1.33 and 1.36 eV, respectively) that far exceeded expected values (0.3 and 0.65 eV, respectively) based on enzyme kinetics alone. Our results suggest that the temperature-dependence of nitrogen fixation may lead to amplified thermal scaling of GPP in stream ecosystems. Efforts to incorporate temperature-resource interactions into metabolic models are needed to help predict ecosystem responses to warming.

Authors

Welter, J. R., St. Catherine University, USA, jrwelter@stkate.edu

Williamson, T. J., Montana State University, USA, tanner.williamson@gmail.com

Cross, W. F., Montana State University, USA, wyatt.cross@montana.edu

Hood, J. M., Montana State University, USA, hoodx008@umn.edu

Benstead, J. P., University of Alabama, USA, jbenstead@as.ua.edu

Huryn, A. D., University of Alabama, USA, huryn@bama.ua.edu

Johnson, P. W., University of Alabama, USA, Pjohnson@eng.ua.edu

Ahles, A. M., St. Catherine University, USA, amahles@stkate.edu

Goldschmidt, J. B., St. Catherine University, USA, jbgoldschmidt@stkate.edu

Details

Oral presentation

Session #:024
Date: 5/22/2014
Time: 14:15
Location: E 145 - 146

Presentation is given by student: No