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Project Progress

This project examines relationship between hydrological and biological diversity within a mesophilic, sufide-rich spring system. We are focusing on a set of springs in which the water composition, temperature and discharge are variable because of the mixing of groundwater from different sources. These springs are terrestrial analogues for late-stage groundwater discharge at the Martian surface. The site was chosen chosen based on geologic history, extant biology, and the accretion of large calcite ‘mounds’ created by spring water discharge. The mounds allow us to relate the extant biological communities to that preserved in the calcite mounds and to discern taphonomic processes affecting biosignature preservation. This allows us to identify the potential and challenge of finding a fossil record of life at spring deposits on other planets.
Even though the springs all lie within a few tens of meters of each other there is a wide range of hydrogeochemical properties and this is reflected in the biological communities that inhabit the springs. The dominant biology present at each spring is composed of sulfur-oxidizing members of both the Epsilon- and Gammaproteobacteria as revealed by 16S rRNA analysis; lipid analysis of the biomass confirms this observation. To date we have been monitoring the hydrology of these springs for four years (discharge, temperature, geochemistry, water source as identified with stable isotopes of O and H).
These measurements allowed us to develop theoretical models for the hydrogeology associated with the springs (Rowland et al., 2008) and hence to understand their evolution in time (Manga and Rowland 2009), and the origin of spatial variability, of water temperature and geochemistry. We also have biological samples from a year period. In addition to differences between individual springs, we also see seasonal variations in the biological communities at a given spring.