Biosignature reservoirs in the Rozel Point tar seeps at Great Salt Lake, Utah

On the north shore of Great Salt Lake, Utah, USA, naturally occurring tar seeps at Rozel Point provide an opportunity to study a petroleum-rich environment adjacent to a hypersaline desert ecosystem. Currently, this terminal lake is shrinking, and the Rozel tar spreads along the surface of the dry lakebed, forming seeps that are numerous and variable in size. These seeps result from high molecular weight hydrocarbons migrating up through cracks and fissures along faulted basalt and limestone. Our gas analysis in the seeps revealed emissions of methane and carbon dioxide, suggesting microbial activities such as petroleum degradation and methanogenesis. To probe the microbial diversity, we collected Rozel petroleum samples from three distinctive seeps and extracted DNA then probed the taxonomic diversity with specific primers (16S rRNA genes of bacteria and archaea; 18S rRNA genes of eukaryotes; Internal Transcribed Spacers 1 and 2 for fungi). Sequencing and a phylogenetic analysis demonstrated a robust microbial community in the tar including halophilic species originating from the nearby lake water and sediment as well as species that may degrade the petroleum. However, most of the bacterial signals were indicative of animal-related microbiota, likely introduced by the tar-entrapped fauna or from the surrounding ranchland. A large portion of the fungal biosignatures were related to plant-associated species from the local steppe. Taken together, the Rozel tar seeps capture a unique snapshot of the biology in the area, which may be a compelling rationale for studying tar seeps on Earth as biosignature traps. Also, we share astrobiology insights for considering potential life on other space bodies: this hydrocarbon reservoir may serve as an analog for studies of similar biosignature-collecting asphalt seeps.