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Abstract The CO2flux () from lakes to the atmosphere is a large component of the global carbon cycle and depends on the air–water CO2concentration gradient (ΔCO2) and the gas transfer velocity (k). Both ΔCO2andkcan vary on multiple timescales and understanding their contributions to is important for explaining variability in fluxes and developing optimal sampling designs. We measured and ΔCO2and derivedkfor one full ice‐free period in 18 lakes using floating chambers and estimated the contributions of ΔCO2andkto variability. Generally,kcontributed more than ΔCO2to short‐term (1–9 d) variability. With increased temporal period, the contribution ofkto variability decreased, and in some lakes resulted in ΔCO2contributing more thankto variability over the full ice‐free period. Increased contribution of ΔCO2to variability over time occurred across all lakes but was most apparent in large‐volume southern‐boreal lakes and in deeper (> 2 m) parts of lakes, whereaskwas linked to variability in shallow waters. Accordingly, knowing the variability of bothkand ΔCO2over time and space is needed for accurate modeling of from these variables. We conclude that priority in assessments should be given to direct measurements of at multiple sites when possible, or otherwise from spatially distributed measurements of ΔCO2combined withk‐models that incorporate spatial variability of lake thermal structure and meteorology.
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Diel variation in CO2 flux is substantial in many lakes
Abstract Lakes play a significant role in the global carbon cycle, acting as sources and sinks of carbon dioxide (CO2). In situ measurements of CO2flux (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 FCO2across lakes. We sampled 21 lakes over 41 campaigns and measured FCO2at 4‐h intervals over a full diel cycle. Rates of FCO2ranged from −3.16 to 4.39 mmol m−2 h−1. Integrated over a day, FCO2ranged from −381.68 to 878.49 mg C m−2d−1(mean = 76.54) across campaigns. We identified three characteristic diel patterns in FCO2related 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.
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- Award ID(s):
- 2327030
- PAR ID:
- 10648227
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Limnology and Oceanography Letters
- Volume:
- 10
- Issue:
- 6
- ISSN:
- 2378-2242
- Format(s):
- Medium: X Size: p. 977-989
- Size(s):
- p. 977-989
- Sponsoring Org:
- National Science Foundation
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