09 Nov 2022
09 Nov 2022
Status: this preprint is currently under review for the journal BG.

Physical and stoichiometric controls on stream respiration in a headwater stream

Jancoba Dorley1, Joel Singley2,3, Tim Covino4,5, Kamini Singha6, Michael Gooseff7,8, and Ricardo González-Pinzón1 Jancoba Dorley et al.
  • 1Civil, Construction and Environmental Engineering, University of New Mexico, Albuquerque, NM USA
  • 2Environmental Studies Program, University of Colorado, Boulder, CO USA
  • 3Biology, Marine Biology, and Environmental Science, Roger Williams University, Bristol, RI USA
  • 4Ecosystem Science and Sustainability, Colorado State University, Fort Collins, CO USA
  • 5Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, MT USA
  • 6Geology and Geological Engineering, Hydrologic Science and Engineering Program, Colorado School of Mines, Golden, CO USA
  • 7Civil, Environmental and Architectural Engineering, University of Colorado, Boulder, CO USA
  • 8Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO USA

Abstract. Many studies in ecohydrology focusing on hydrologic transport argue that longer residence times across a stream ecosystem should consistently result in higher biological uptake of carbon, nutrients, and oxygen. This consideration does not incorporate the potential for biologically mediated reactions to be limited by stoichiometric imbalances. Based on the relevance and co-dependences between hydrologic exchange, stoichiometry, and biological uptake, and acknowledging the limited amount of field studies available to determine their net effects on the retention and export of resources, we quantified how microbial respiration is controlled by the interactions and supply of essential nutrients needed (C, N, P) in a headwater stream in Colorado, USA. For this, we conducted two rounds of nutrient experiments, each consisting of four sets of continuous injections of Cl- as a conservative tracer, resazurin as a proxy for aerobic respiration, and one of the following nutrient treatments: a) N, b) N+C, c) N+P, and d) C+N+P. Nutrient treatments were considered as known system modifications to alter metabolism, and statistical tests helped identify the relationships between hydrologic transport and respiration metrics. We found that as discharge changed significantly between rounds and across stoichiometric treatments, a) transient storage mainly occurred in side pools along the main channel and was proportional to discharge, and b) microbial respiration remained similar between rounds and across stoichiometric treatments. Together, our results indicate that residence time alone could be a weak predictor of stream respiration due to the relevance of local and dynamic variations in stoichiometric conditions.

Jancoba Dorley et al.

Status: open (until 21 Dec 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on bg-2022-214', Anonymous Referee #1, 17 Nov 2022 reply
  • RC2: 'Comment on bg-2022-214', Anonymous Referee #2, 22 Nov 2022 reply

Jancoba Dorley et al.

Jancoba Dorley et al.


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Short summary
We quantified how microbial respiration is controlled by discharge and the supply of C, N, and P in a stream. We ran two rounds of experiments adding a conservative tracer, an indicator of aerobic respiration, and nutrient treatments: a) N, b) N+C, c) N+P, and d) C+N+P. Microbial respiration remained similar between rounds and across nutrient treatments, suggesting that both exposure times and nutrient composition control microbial metabolic activity in stream ecosystems.