Qipei Shangguan, Robert A. Payn, Robert O. Hall Jr, Fischer L. Young, H. Maurice Valett, Michael D. DeGrandpre
{"title":"Divergent metabolism estimates from dissolved oxygen and inorganic carbon: Implications for river carbon cycling","authors":"Qipei Shangguan, Robert A. Payn, Robert O. Hall Jr, Fischer L. Young, H. Maurice Valett, Michael D. DeGrandpre","doi":"10.1002/lno.12666","DOIUrl":null,"url":null,"abstract":"<p>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 (CO<sub>2</sub>) 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 (PQ<sub>E</sub> and RQ<sub>E</sub>). We observed that metabolism estimates from DIC varied more between single- and two-station approaches than estimates from DO. Due to carbonate buffering, CO<sub>2</sub> is slower to equilibrate with the atmosphere compared to DO, likely incorporating a longer distance of upstream heterogeneity. Reach-averaged PQ<sub>E</sub> ranged from 1.5 to 2.0, while RQ<sub>E</sub> ranged from 0.8 to 1.5. Gross primary production from DO was larger than that from DIC, as was net ecosystem production by <span></span><math>\n <mrow>\n <mn>100</mn>\n <mspace></mspace>\n <mtext>mmol</mtext>\n <mspace></mspace>\n <msup>\n <mi>m</mi>\n <mrow>\n <mo>−</mo>\n <mn>2</mn>\n </mrow>\n </msup>\n <mspace></mspace>\n <msup>\n <mi>d</mi>\n <mrow>\n <mo>−</mo>\n <mn>1</mn>\n </mrow>\n </msup>\n </mrow></math>. The river was autotrophic based on DO but heterotrophic based on DIC, complicating our understanding of how metabolism regulated CO<sub>2</sub> production. We suggest future studies simultaneously model metabolism from DO and DIC to understand carbon processing in rivers.</p>","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"69 9","pages":"2211-2228"},"PeriodicalIF":3.8000,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/lno.12666","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Limnology and Oceanography","FirstCategoryId":"89","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1002/lno.12666","RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"LIMNOLOGY","Score":null,"Total":0}
引用次数: 0
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 (PQE and RQE). We observed that metabolism estimates from DIC varied more between single- and two-station approaches than estimates from DO. Due to carbonate buffering, CO2 is slower to equilibrate with the atmosphere compared to DO, likely incorporating a longer distance of upstream heterogeneity. Reach-averaged PQE ranged from 1.5 to 2.0, while RQE ranged 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 CO2 production. We suggest future studies simultaneously model metabolism from DO and DIC to understand carbon processing in rivers.
期刊介绍:
Limnology and Oceanography (L&O; print ISSN 0024-3590, online ISSN 1939-5590) publishes original articles, including scholarly reviews, about all aspects of limnology and oceanography. The journal''s unifying theme is the understanding of aquatic systems. Submissions are judged on the originality of their data, interpretations, and ideas, and on the degree to which they can be generalized beyond the particular aquatic system examined. Laboratory and modeling studies must demonstrate relevance to field environments; typically this means that they are bolstered by substantial "real-world" data. Few purely theoretical or purely empirical papers are accepted for review.