Diel variation of CH₄ and CO₂ dynamics in two contrasting temperate lakes

ABSTRACT

The concurrent short-term fluctuations of methane (CH₄) and carbon dioxide (CO₂) concentrations and emissions in lakes are not well studied. Quantifying the differences in daytime versus nighttime dynamics may provide information about the controls over greenhouse gas production and may have relevance to lake carbon budgets. In this study, the diel variation of CH₄ and CO₂ emissions and concentration patterns were determined along the water column of 2 temperate lakes with different trophic states during July 2015. The results showed that the shallow eutrophic lake had significantly higher CH₄ and CO₂ releases than the deep oligo-mesotrophic lake. No significant diel fluctuations were observed in atmospheric CH₄ emissions from either lake or in CO₂ emission from the oligo-mesotrophic lake, but significantly higher CO₂ emission from the eutrophic lake occurred during the daytime compared to nighttime. Based on a diffusion–reaction model, it was possible to estimate the diel variation of the sources and sinks of dissolved CH₄ throughout the water column, suggesting lateral transport is a potential source of CH₄ in oxygenated water layers in the oligo-mesotrophic lake. Sources and sinks throughout the water column should be considered in future studies for a better understanding of CH₄ dynamics within the lakes.

KEYWORDS:

• carbon metabolism
• diffusion–reaction model
• greenhouse gases
• trophic state

Acknowledgements

We thank Gonzalo Idoate Santaolalla, Michael Sachtleben, Sonia Herrero Ortega, and Lars Ganzert for field assistance, and Carola Kasprzak and Ute Beyer for lab assistance.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by Comisión Nacional de Investigación Científica y Tecnológica, Chile (Fondecyt Grant Number 11160391); Consejo Nacional de Ciencia y Tecnología, Mexico (Grant Numbers 233369 and 232083). Leibniz-Gemeinschaft: [Grant Number SAW-2011-IGB-2]; Leibniz-Gemeinschaft: [Grant Number SAW-2012-IGB 4167].