Tuesday, 25 February 2014
New evidence in aerobiology challenges the assumption that geographical isolation is an effective barrier to microbial transport. However, given the uncertainty with which aerobiological organisms are recruited into existing communities, the ultimate impact of microbial dispersal is difficult to assess. Here we use molecular genetic approaches to examine microbial communities inhabiting fumarolic soils on Mt. Erebus, the southernmost geothermal site on Earth, to evaluate the ecological significance of global-scale microbial dispersal. There, hot, fumarolic soils provide an effective environmental filter to test the viability of organisms that have been distributed via aeolian transport over geological time. We find that cosmopolitan thermophiles dominate the surface, whereas endemic Archaea and members of poorly understood Bacterial candidate divisions dominate the immediate subsurface. These results imply that aeolian processes readily disperse viable organisms globally, where they are incorporated into pre-existing complex communities of endemic and cosmopolitan taxa. more...
Wednesday, 26 February 2014
Deserts are the most abundant and persistent terrestrial biome. Environmental stress limits higher plants and animals and so microbial communities dominate in soils and rock surfaces. These form the critical zone of biological interaction in deserts and they perform the majority of ecosystem functions. These communities are critical to stabilization of the desert mineral substrate, and their disturbance can contribute to massive destabilization and mobilization of dust. This results in dust storms that are transported across inter-continental distances. Dust mobilization impacts local biotic interactions and land use, but also leads to problems that manifest at regional scales, such as altered hydrological regimes, changes to oceanic nitrogen fixation, coral reef senescence and increasingly as a threat to human health. more...