Abstract
Lakes play a significant role in the global carbon cycle, acting as sources and sinks of carbon dioxide (CO2). In situ measurements of CO2 flux (FCO2) from lakes have generally been collected during daylight, despite indications of significant diel variability. This introduces bias when scaling up to whole-lake annual aquatic carbon budgets. We conducted an international sampling program to ascertain the extent of diel variation in FCO2 across lakes. We sampled 21 lakes over 41 campaigns and measured FCO2 at 4-h intervals over a full diel cycle. Rates of FCO2 ranged from −3.16 to 4.39 mmol m−2 h−1. Integrated over a day, FCO2 ranged from −381.68 to 878.49 mg C m−2 d−1 (mean = 76.54) across campaigns. We identified three characteristic diel patterns in FCO2 related to trophic status and show that for half of the campaigns, daily flux estimates were biased by > 50% if based on a single (daytime) measurement.
| Original language | English |
|---|---|
| Pages (from-to) | 977-989 |
| Number of pages | 13 |
| Journal | Limnology and Oceanography Letters |
| Volume | 10 |
| Issue number | 6 |
| DOIs | |
| State | Published - Dec 2025 |
Funding
This work is the result of an international team science effort facilitated by the Global Lake Ecological Observatory Network. In addition to the listed co-authors, many of the GLEON Lake Ecological Observatory Network community contributed to earlier stages of the DC-FLUX project, and we thank them for their input. Daniel Mercado provided the CO2 atmospheric data and Seán Kelly provided analysis assistance to Elvira de Eyto. Robyn L. Smyth, Ankur R. Desai, Angela Baldocchi, Cayelan C. Carey, and David Reed acknowledge support from U.S. National Science Foundation from DEB-1754271, DEB-2025982, DEB-1440297, DEB-2327030, and the AGS Postdoctoral Fellowship award to David Reed. Robyn L. Smyth completed this work while serving at U.S. National Science Foundation. Any opinion, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the U.S. National Science Foundation or U.S. Federal government. Long-term funding from the Norwegian Environment Agency supported climate monitoring at Langtjern (Contract No. 22047069) and Eivind Ekholt Andersen assisted with this sampling. Data collection from Estonian lakes was supported by the Estonian Research Council grants (PSG32, PRG1167, PRG709, PUT1598, and IUT21-2). Anna Lupon was supported by the project FLUPRINT (EUR2023-143456), MICIU/AEI/FEDER UE, and Next Generation funding. Biel Obrador and Rafael Marcé acknowledge funding for the data collection at Sau reservoir from Project PID2020-114024GB-C31 and PID2020-114024GB-C32, funded by MCIN/AEI/10.13039/501100011033/. Work by David Bastviken and David Rudberg were funded by the Knut and Alice Wallenberg Foundation (Grant 2016.0083), the European Research Council H2020 (Grant 725546), the Swedish Research Council (Grant 2016-04829), and FORMAS (Grant 2018-01794). The teams associated with these projects are acknowledged for valuable assistance. Gesa A. Weyhenmeyer received financial support from the Swedish Research Council (VR Grant No. 2020-03222 and FORMAS Grant No. 2020-01091). R. Iestyn Woolway was supported by a UKRI Natural Environment Research Council Independent Research Fellowship (NE/T011246/1). José Fernandes Bezerra-Neto and Ludmila S. Brighenti acknowledge support from Long-Term Ecological Research Project (PELD—Rio Doce, Process No. 441481/2016-7—Conselho Nacional de Desenvolvimento Científico e Tecnológico). Sari Juutinen was funded by the Research Council of Finland (RCF) (Grant numbers 334509 and 347662). Lauri Heiskanen, Valtteri Hyöky, Md Shamsuzzaman, Hanna Salomaa and Lauha Jämsä are acknowledged for their help with the field work at FMI lakes Kaamanen and Pallasjärvi. The work on Pallasjärvi was funded by the ICOS Finland and the ACCC Flagship funding by RCF (Grant No. 337552). James A. Rusak thanks Nevan Baus for assistance in the field and acknowledges support from a Natural Science and Engineering Council of Canada Discovery Grant (RGPIN/05199-2018) and the Ontario Ministry of the Environment. Sarian Kosten’s contribution was supported by NWO-TTW Project No. 18661 and NWO-VIDI 203.098. Rachel M. Pilla was supported by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Water Power Technologies Office, and Environmental Sciences Division at Oak Ridge National Laboratory. Oak Ridge National Laboratory is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725. We used artificial intelligence (ChatGPT) to assist with debugging code and generation of figs. Artificial intelligence was not used for any text generation or editing. We thank the associate editor and two anonymous reviewers for their helpful comments on an earlier draft. This work is the result of an international team science effort facilitated by the Global Lake Ecological Observatory Network. In addition to the listed co‐authors, many of the GLEON Lake Ecological Observatory Network community contributed to earlier stages of the DC‐FLUX project, and we thank them for their input. Daniel Mercado provided the CO atmospheric data and Seán Kelly provided analysis assistance to Elvira de Eyto. Robyn L. Smyth, Ankur R. Desai, Angela Baldocchi, Cayelan C. Carey, and David Reed acknowledge support from U.S. National Science Foundation from DEB‐1754271, DEB‐2025982, DEB‐1440297, DEB‐2327030, and the AGS Postdoctoral Fellowship award to David Reed. Robyn L. Smyth completed this work while serving at U.S. National Science Foundation. Any opinion, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the U.S. National Science Foundation or U.S. Federal government. Long‐term funding from the Norwegian Environment Agency supported climate monitoring at Langtjern (Contract No. 22047069) and Eivind Ekholt Andersen assisted with this sampling. Data collection from Estonian lakes was supported by the Estonian Research Council grants (PSG32, PRG1167, PRG709, PUT1598, and IUT21‐2). Anna Lupon was supported by the project FLUPRINT (EUR2023‐143456), MICIU/AEI/FEDER UE, and Next Generation funding. Biel Obrador and Rafael Marcé acknowledge funding for the data collection at Sau reservoir from Project PID2020‐114024GB‐C31 and PID2020‐114024GB‐C32, funded by MCIN/AEI/ 10.13039/501100011033 /. Work by David Bastviken and David Rudberg were funded by the Knut and Alice Wallenberg Foundation (Grant 2016.0083), the European Research Council H2020 (Grant 725546), the Swedish Research Council (Grant 2016‐04829), and FORMAS (Grant 2018‐01794). The teams associated with these projects are acknowledged for valuable assistance. Gesa A. Weyhenmeyer received financial support from the Swedish Research Council (VR Grant No. 2020‐03222 and FORMAS Grant No. 2020‐01091). R. Iestyn Woolway was supported by a UKRI Natural Environment Research Council Independent Research Fellowship (NE/T011246/1). José Fernandes Bezerra‐Neto and Ludmila S. Brighenti acknowledge support from Long‐Term Ecological Research Project (PELD—Rio Doce, Process No. 441481/2016‐7—Conselho Nacional de Desenvolvimento Científico e Tecnológico). Sari Juutinen was funded by the Research Council of Finland (RCF) (Grant numbers 334509 and 347662). Lauri Heiskanen, Valtteri Hyöky, Md Shamsuzzaman, Hanna Salomaa and Lauha Jämsä are acknowledged for their help with the field work at FMI lakes Kaamanen and Pallasjärvi. The work on Pallasjärvi was funded by the ICOS Finland and the ACCC Flagship funding by RCF (Grant No. 337552). James A. Rusak thanks Nevan Baus for assistance in the field and acknowledges support from a Natural Science and Engineering Council of Canada Discovery Grant (RGPIN/05199‐2018) and the Ontario Ministry of the Environment. Sarian Kosten’s contribution was supported by NWO‐TTW Project No. 18661 and NWO‐VIDI 203.098. Rachel M. Pilla was supported by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Water Power Technologies Office, and Environmental Sciences Division at Oak Ridge National Laboratory. Oak Ridge National Laboratory is managed by UT‐Battelle, LLC, for the U.S. Department of Energy under contract DE‐AC05‐00OR22725. We used artificial intelligence (ChatGPT) to assist with debugging code and generation of figs. Artificial intelligence was not used for any text generation or editing. We thank the associate editor and two anonymous reviewers for their helpful comments on an earlier draft. 2