2002 Annual Science Report
NASA Ames Research Center Reporting | JUL 2001 – JUN 2002
Ecosystem to Biosphere Modeling
We constructed a model to simulate C, O, and S cycles, and growth of cyanobacteria and sulfur bacteria in a stratified hypersaline mat. The aim was to simulate microbial effects on the atmospheric chemistry of early Earth. Inputs to the mat system include photosynthetically active radiation (PAR), near infrared radiation (NIR), and temperature. Attenuation of PAR with each layer is modeled, and NIR attenuation depends on the abundance of bacteriochlorophyll a. The bacterial groups whose metabolism and growth are simulated include cyanobacteria (CYA), purple sulfur bacteria (PSB), colorless sulfur bacteria (CSB), and sulfur reducing bacteria (SRB). Growth of CYA occurs by either oxygenic or anoxygenic photosynthesis (AP), depending on the available substrate (O2 or H2S). PSB growth occurs by AP using NIR and H2S or by chemosynthesis (CH), using O2 and H2S. Growth of CSB occurs via CH, also using O2 and H2S. SRB growth occurs via anaerobic CH utilizing SO4 2- and creating H2S in the process. The model consists of 10 layers (1 mm each), and gains density as biomass increases. Gas diffusion occurs between successive layers. The model was constructed in a Stellatm environment, and will be updated to include methanogens and decomposition before being programmed into an environment that is compatible with atmospheric simulations of early Earth.
PROJECT MEMBERS:Christopher Potter
RELATED OBJECTIVES:Objective 5.0
Describe the sequences of causes and effects associated with the development of Earth's early biosphere and the global environment.
Define how ecophysiological processes structure microbial communities, influence their adaptation and evolution, and affect their detection on other planets.
Determine the resilience of local and global ecosystems through their response to natural and human-induced disturbances.
Model the future habitability of Earth by examining the interactions between the biosphere and the chemistry and radiation balance of the atmosphere.