Microbial transport in volcanic tuff Rainier Mesa, Nevada test site
Water flowing along fractures may affect the mobilization of microorganisms in volcanic tuff and impose conditions that are different from those in the rock matrix away from water flow paths. To address the potential for bacterial transport with water in deep fractured tuffs, flow water and six rock samples were taken progressively farther from a deep subsurface fracture flow system for microbiological and geological comparisons. Differences in the composition of microbiota among sites appeared to be the result of proximity to flow water. The microbiota in the vicinity of the fracture water flow path, in contrast to that in rock farthest away, consisted of greater morphological and physiological diversity suggesting a more complex community structure; Bacterial transport was tested, in water-saturated tuff cores of differing lithology. Bacterial transport occurred in cores permeable to water and was impeded in impermeable tuffs. Bacterial transport routes in permeable cores was determined by bacterial breakthrough patterns. Bacteria appeared to be transported through connected macropores or fractures in tuff cores. Laboratory and field results demonstrated that bacteria were transported with water predominantly along preferred water flow paths in rock.