Preprints
https://doi.org/10.5194/bg-2022-214
https://doi.org/10.5194/bg-2022-214
09 Nov 2022
 | 09 Nov 2022
Status: a revised version of this preprint is currently under review for the journal BG.

Physical and stoichiometric controls on stream respiration in a headwater stream

Jancoba Dorley, Joel Singley, Tim Covino, Kamini Singha, Michael Gooseff, and Ricardo González-Pinzón

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: final response (author comments only)

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
    • AC1: 'Reply on RC1', Ricardo González-Pinzón, 14 Dec 2022
  • RC2: 'Comment on bg-2022-214', Anonymous Referee #2, 22 Nov 2022
    • AC2: 'Reply on RC2', Ricardo González-Pinzón, 14 Dec 2022

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.
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