Can a Red Wood-Ant Nest Be Associated with Fault-Related CH₄ Micro-Seepage? A Case Study from Continuous Short-Term...

Area of Science:

• Geochemistry
• Environmental Science
• Ecology

Background:

• Methane (CH₄) is a potent greenhouse gas with diverse sources.
• Red wood-ant (RWA) nests are recognized as micro-ecosystems with potential for microbial activity.

Purpose of the Study:

• To investigate methane sources and isotopic signatures within RWA nests.
• To assess the role of RWA nests in methane emissions and as potential indicators of geological methane seepage.

Main Methods:

• High-resolution in-situ sampling of ambient air and RWA nest gas.
• Measurement of methane (CH₄) concentrations and stable carbon isotope ratios (δ¹³C-CH₄).

Main Results:

• Two distinct δ¹³C-CH₄ signatures were detected: -69‰ (microbial) and -37‰ (potentially fault-related).
• Methane degassing from nests was not linked to earth tides, micro-earthquakes, or RWA activity.
• The -37‰ signature suggests CH₄ from thermogenic or abiotic sources, possibly linked to local geology or magmatic activity.

Conclusions:

• RWA nests are confirmed hot-spots for microbial methane production.
• Fault-related methane seepage can infiltrate RWA nests, indicated by a unique isotopic signature.
• RWA nests should be considered in methane emission budgets and as biological indicators for abiotic methane sources.