Autochthonous dissolved organic matter potentially fuels methane ebullition from experimental lakes

Yongqiang Zhou; Lei Zhou; Yunlin Zhang; Javier Garcia de Souza; David C Podgorski; Robert G M Spencer; Erik Jeppesen; Thomas A Davidson

doi:10.1016/j.watres.2019.115048

Autochthonous dissolved organic matter potentially fuels methane ebullition from experimental lakes

Water Res. 2019 Dec 1:166:115048. doi: 10.1016/j.watres.2019.115048. Epub 2019 Sep 5.

Authors

Yongqiang Zhou¹, Lei Zhou², Yunlin Zhang², Javier Garcia de Souza³, David C Podgorski⁴, Robert G M Spencer⁵, Erik Jeppesen⁶, Thomas A Davidson⁷

Affiliations

¹ State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 210008, China; University of Chinese Academy of Sciences, Beijing, 100049, China. Electronic address: yqzhou@niglas.ac.cn.
² State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 210008, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
³ Instituto de Limnología 'Dr. Raúl A. Ringuelet' (ILPLA) (UNLP-CONICET), Boulevard 120 y 62, CC 712, La Plata, Provincia de Buenos Aires, Argentina.
⁴ Pontchartrain Institute for Environmental Sciences, Department of Chemistry, University of New Orleans, New Orleans, 70148, Louisiana, USA.
⁵ Department of Earth, Ocean and Atmospheric Science, Florida State University, Tallahassee, 32306, Florida, USA.
⁶ Department of Bioscience and Arctic Research Centre, Aarhus University, Vejlsøvej 25, DK-8600, Silkeborg, Denmark; Sino-Danish Centre for Education and Research, Beijing, 100190, China.
⁷ Department of Bioscience and Arctic Research Centre, Aarhus University, Vejlsøvej 25, DK-8600, Silkeborg, Denmark. Electronic address: thd@bios.au.dk.

PMID: 31518733
DOI: 10.1016/j.watres.2019.115048

Abstract

Shallow lakes are hotspots for carbon processing and important natural sources of methane (CH₄) emission. Ebullitive CH₄ flux may constitute the overwhelming majority of total CH₄ flux, but the episodic nature of ebullition events makes determining both quantity and the controlling factors challenging. Here we used the world's longest running shallow-lake mesocosm facility, where the experimental treatments are low and high nutrients crossed with three temperatures, to investigate the quantity and drivers of CH₄ ebullition. The mean CH₄ ebullition flux in the high nutrient treatment (41.5 ± 52.3 mg CH₄-C m^-2 d^-1) mesocosms was significantly larger than in the low nutrient treatment (3.6 ± 5.4 mg CH₄-C m^-2 d^-1) mesocosms, varying with temperature scenarios. Over eight weeks from June to August covered here warming resulted in a weak, but insignificant enhancement of CH₄ ebullition. We found significant positive relationships between ebullition and chlorophyll-a, dissolved organic carbon (DOC), biodegradable DOC, δ²H, δ¹⁸O and δ¹³C-DOC, autochthonous dissolved organic matter (DOM) fluorescent components, and a fraction of lipids, proteins, and lignins revealed using ultrahigh-resolution mass spectrometry, and a negative relationship between ebullitive CH₄ flux and the percentage volume inhabited of macrophytes. A 24 h laboratory bio-incubation experiment performed at room temperature (20 ± 2 °C) in the dark further revealed a rapid depletion of algal-DOM concurrent with a massive increased CH₄ production, whereas soil-derived DOM had a limited effect on CH₄ production. We conclude that eutrophication likely induced the loss of macrophytes and increase in algal biomass, and the resultant accumulation algal derived bio-labile DOM potentially drives enhanced outgassing of ebullitive CH₄ from the shallow-lake mesocosms.

Keywords: Bio-labile; Chromophoric dissolved organic matter (CDOM); Greenhouse gases; Methane (CH(4)) ebullition; Parallel factor analysis (PARAFAC); Ultrahigh resolution mass spectrometry.

MeSH terms

Carbon
Eutrophication
Lakes*
Methane*
Temperature

Substances

Carbon
Methane