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Title: Divergent metabolism estimates from dissolved oxygen and inorganic carbon: Implications for river carbon cycling
Abstract Rivers efficiently collect, process, and transport terrestrial‐derived carbon. River ecosystem metabolism is the primary mechanism for processing carbon. Diel cycles of dissolved oxygen (DO) have been used for decades to infer river ecosystem metabolic rates, which are routinely used to predict metabolism of carbon dioxide (CO2) with uncertainties of the assumed stoichiometry ranging by a factor of 4. Dissolved inorganic carbon (DIC) has been less used to directly infer metabolism because it is more difficult to quantify, involves the complexity of inorganic carbon speciation, and as shown in this study, likely requires a two‐station approach. Here, we developed DIC metabolism models using single‐ and two‐station approaches. We compared metabolism estimates based on simultaneous DO and DIC monitoring in the Upper Clark Fork River (USA), which also allowed us to estimate ecosystem‐level photosynthetic and respiratory quotients (PQEand RQE). We observed that metabolism estimates from DIC varied more between single‐ and two‐station approaches than estimates from DO. Due to carbonate buffering, CO2is slower to equilibrate with the atmosphere compared to DO, likely incorporating a longer distance of upstream heterogeneity. Reach‐averaged PQEranged from 1.5 to 2.0, while RQEranged from 0.8 to 1.5. Gross primary production from DO was larger than that from DIC, as was net ecosystem production by . The river was autotrophic based on DO but heterotrophic based on DIC, complicating our understanding of how metabolism regulated CO2production. We suggest future studies simultaneously model metabolism from DO and DIC to understand carbon processing in rivers.  more » « less
Award ID(s):
2324877 2324878 2428705
PAR ID:
10635904
Author(s) / Creator(s):
; ; ; ; ;
Publisher / Repository:
Associated Sciences of Limnology and Oceanography
Date Published:
Journal Name:
Limnology and Oceanography
Volume:
69
Issue:
9
ISSN:
0024-3590
Page Range / eLocation ID:
2211 to 2228
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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