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Project Progress

We have developed a simulation model called MBGC (Microbial BioGeoChemistry) to infer effects of major environmental controllers on microbial community structure and function (Decker and Potter, 2002). Microbial growth, metabolic reaction rates, and mass flows are represented within and between vertical sediment layers of a microbial mat in the hypersaline environment (Figure 1). In addition, diel cycles are simulated to capture natural variation in environmental boundary conditions, such as light and temperature. The fundamental structure of our MBGC simulation model follows that of a previous model (de Wit et al., 1995) of population dynamics and biogeochemistry within benthic mats containing cyanobacteria (CYN), purple sulfur bacteria (PSB) and colorless sulfur bacteria (CSB). Specific additions were incorporated recently into our MBGC model in order to (1) represent CYN photosynthesis metabolism operating as a light-driven quantum efficiency function, (2) complete the microbial sulfur cycle, and (3) enable a comparison of the model predictions to hourly field-measured biogeochemical fluxes. More specifically, we have added sulfate-reducing bacteria (SRB) to MBGC, which can consume organic carbon and produce the H₂S oxidized by PSB and CSB. In addition, molecular hydrogen (H₂), decomposition of dead organic matter (DOM), CO₂ fluxes, and realistic (time-varying) temperature and light controls on major metabolic pathways are included in MBGC as extensions of the original de Wit model structure.

Decker K.L.M. and C. Potter, 2002. Mathematical model of a marine microbial mat ecosystem. Abstracts of the Second Annual Astrobiology Conference. Moffett Field, CA.

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