Methane ebullition fluxes and temperature sensitivity in a shallow lake

Area of Science:

• Environmental Science
• Geochemistry
• Limnology

Background:

• Inland waters are significant sources of atmospheric methane (CH4).
• Methane ebullition is a key CH4 emission pathway from aquatic ecosystems.
• Data on CH4 ebullition flux (eFCH4) and temperature sensitivity (Q10) in shallow lakes are limited, causing uncertainties in climate change impact assessments.

Purpose of the Study:

• To quantify the magnitude and drivers of CH4 ebullition and diffusion fluxes in subtropical Lake Chaohu.
• To assess the spatial and seasonal variations of eFCH4.
• To determine the temperature sensitivity (Q10) of eFCH4 and identify its ecosystem-level drivers.

Main Methods:

• Utilized a real-time portable greenhouse gas (GHG) analyzer with a floating chamber method.
• Conducted measurements at 18 sites across four seasons in Lake Chaohu.
• Employed whole-lake mass balance calculations and meta-analysis for broader comparisons.

Main Results:

• Methane ebullition flux (eFCH4) was the dominant CH4 emission pathway (73.0%) in Lake Chaohu.
• Higher eFCH4 was observed in western and eastern lake zones, and nearshore areas compared to middle and pelagic zones.
• eFCH4 exhibited significant seasonal variation, peaking in summer, and showed strong temperature dependence.
• Sediment total organic carbon (STOC) was identified as a key driver of ecosystem-level Q10 for eFCH4.

Conclusions:

• Methane ebullition is a critical pathway for CH4 release from shallow lakes, significantly influenced by spatial, seasonal, and temperature factors.
• Sediment total organic carbon and latitude are important ecosystem-level regulators of eFCH4 temperature sensitivity.
• Increasing climate change and human activities may enhance eFCH4 in shallow lake ecosystems, particularly in high-latitude regions.