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Project Progress

Field research on the freshwater bacteria of Cuatro Cienegas, Mexico (Siefert). These communities are good proxies for early earth type bacterially-dominated systems. To understand the community dynamics that lead to microbialite (general term for structures produced by microbial precipitation) the metagenomes of two microbialites, from two separate regions of the system were performed using 454 sequencing technology. Analysis of both the viral and bacterial components are well underway. An oral presentation on “Viral Metagenomics of the Stromatolites of Cuatro Ciénegas” was given at AbSciCon 2006. Currently, we are concentrating on full microscopic and isotopic description of these two microbialites that will help to better characterize the age and the dynamics of the production of the microbialite structure over time.

Coupling the land surface/ecosystem model to the VPL (Kiang, Crisp, Armstrong). To use the VPL to simulate land vegetation-atmosphere interactions of the Earth since the Carboniferous, we have set up the Community Land Model 3.0 (CLM 3.0) of the National Center for Atmospheric Research (NCAR) to couple with the VPL 1D climate and atmospheric chemistry models. CLM 3.0 simulates land surface hydrology and energy exchange, and vegetation dynamics, including short-term CO₂ and water vapor exchange from photosynthesis and transpiration, seasonal growth and soil biogeochemistry, and vegetation competition and cover change. This model coupling will allow simulation of vegetation cover, surface exchanges and spectral reflectance on an Earth-like planet’s surface.

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Modeling biogenic fluxes from microbial mats (Decker). Microbial mats serve as an example of the dominant lifeform in the Proterozoic, and for extrasolar planets at early stages of biological evolution. A new component of a microbial mat model (MBGC-Microbial BioGeoChemistry) has been added to model the flux out of the mat, through a dynamic diffusive boundary layer into the water, then across the aqueous boundary layer and into the atmosphere. This work is on-going. The diffusive boundary layer has been modified to reflect the changes in height that occur with water velocity changes. Gas flux across the aqueous boundary layer has been modeled, although some fine modifications (with regard to specific gases) are yet upcoming. The eddy-flux portion of the model as well as the fine modifications is the agenda for the upcoming year.

Modeling radiative transfer through vegetation canopies (Kiang). Capture of light for photosynthesis by plants is a function of the canopy’s 3-D spatial structure and the spectral absorption properties of leaves and photosynthetic pigments. Canopy structure determines the albedo and atmospheric energy exchange, and the rate of trace gas exchange as driven by vertical light profiles, the transmittance of radiation to the ground (determining ground temperature), and ultimately both the surface spectral reflectance and atmospheric biosignatures of photosynthesis on a planet’s surface. We are developing a simplified canopy radiative transfer model, derived from a detailed 3D geometric-optical model. A poster was presented at the NCAR CCSM Workshop in June 2006. This model will be a component of simulating coupled biosphere-atmosphere interactions for predicting the cover of different types of photosynthetic organisms over a planet’s surface, and their resultant biosignatures.

Photosynthesis on extrasolar planets (Kiang, Segura, Siefert, Tinetti, Blankenship, Cohen, Meadows). We submitted a paper (Kiang et al., 2006) showing modeled plausible absorbance spectra for photosynthetic pigments adapted to different parent star spectra and other planetary compositions. The paper also explores global productivity for vegetation around stars of different spectral type, and explored potential biosignatures for vegetation using these pigments. We found that anoxygenic photosynthesis could dominate a planet’s land surface for queiescent M stars, even without an atmospheric ozone shield.