# Lipid biomarkers reveal dominance of aerobic methanotrophy in a continental serpentinizing system

## TL;DR

This study used lipid biomarkers to show that methane at a serpentinizing site is mainly consumed by aerobic bacteria, not produced by other microbes.

## Contribution

The study provides novel evidence for the dominance of aerobic methanotrophy over methanogenesis in a serpentinizing system.

## Key findings

- Aerobic methanotrophs were the dominant microbial group in methane cycling.
- No evidence of anaerobic methanotrophy or methanogenesis was found.
- Microbial activity may act as a significant methane sink at the site.

## Abstract

Sources and sinks of methane within an advanced serpentinization-influenced system were investigated at the Coast Range Ophiolite Microbial Observatory (CROMO) in Lower Lake, California. Subsurface water-rock reactions at CROMO contribute to unique, high pH groundwaters and substantial methane emissions. We performed lipid analysis on biomass and measured radiocarbon and stable carbon isotopic composition of groundwater to trace the origins and fate of methane. Specific groups of microorganisms involved in methane cycling were identified through analysis of membrane lipid components. Aerobic methanotrophs dominated the samples, with evidence of heterotrophic bacteria but no detection of anaerobic methanotrophy or methanogens. Following these data, microbial activity may be a significant sink but not a major source of methane at this site.