Isotopic Composition of Methane and Inferred Methanogenic Substrates Along a Salinity Gradient in a Hypersaline Microbial Mat System

The importance of hypersaline environments over geological time, the discovery of similar habitats on Mars, and the importance of methane as a biosignature gas combine to compel an understanding of the factors important in controlling methane released from hypersaline microbial mat environments. To further this understanding, changes in stable carbon isotopes of methane and possible methanogenic substrates in microbial mat communities were investigated as a function of salinity here on Earth. Microbial mats were sampled from four different field sites located within salterns in Baja California Sur, Mexico. Salinities ranged from 50 to 106 parts per thousand (ppt).

Pore water and microbial mat samples were analyzed for the carbon isotopic composition of dissolved methane, dissolved inorganic carbon (DIC), and mat material (particulate organic carbon or POC). The POC