Molecular underpinnings of methane emissions from unrestored industrial salt ponds
EMSL Project ID
50701
Abstract
The objective of this proposal is to elucidate the molecular mechanisms of methane production in unrestored salt ponds using metabolomic analysis. Our study site is the South San Francisco Bay, where a long-term restoration project was initiated in 2003 to restore 40,000 acres of industrial salt ponds back to tidal wetlands, to regain lost ecosystem services such as wildlife habitat and flood control. We have sampled sediment from both restored and unrestored salt ponds as well as a nearby historic tidal marsh to investigate carbon cycling and microbial community composition. Unrestored salt ponds produced surprisingly high emissions of the potent greenhouse gas methane as compared to restored salt ponds and historic wetlands, despite high concentrations of sulfate which is typically expected to suppress archaeal methanogenesis. The decrease in methane production upon salt pond restoration could indicate an unappreciated carbon sequestration benefit, and better understanding of carbon cycling in these systems could suggest strategies for mitigating methane emissions from unrestored salt ponds. DNA sequencing of 16S rRNA amplicons and shotgun metagenomes from sediment microbial communities suggests two possible mechanisms for methane generation from the unrestored salt ponds. One is the well-known archaeal methanogenesis pathway, especially the methylotrophic pathway known to be active in other hypersaline environments. The other is degradation of methylphosphonates, a metabolic pathway recently reported to generate methane as a side product in the phosphate-stressed marine environment and explaining the “methane paradox” of methanogenesis in well-oxygenated seawater. Marker gene correlations with methane emissions support both these pathways as possible contributors to salt pond methane production, but the availability of substrates for the pathways in the sediment is unknown. We request access to NMR and mass spec capabilities to determine whether key potential substrates are detectable in our samples, to assess the feasibility of a more in-depth investigation of their abundances across diverse sample types through the EMSL Science Theme call.
Project Details
Project type
Limited Scope
Start Date
2019-02-20
End Date
2019-04-22
Status
Closed
Released Data Link
Team
Principal Investigator