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Project Progress

We have begun investigating the microbial biogeochemistry in lava caves in Halemaumau Crater, part of the active Kilauea volcano in Hawaii Volcanoes National Park. Conditions here of temperature, pH and nutrient availability may be analogous to those that prevailed on much of early Earth. Much of our initial effort has focused on a microbial mat in the entrance of one cave. We have analyzed nutrient concentrations in groundwater in order elucidate the composition and scale of potential inputs to the system. Photosynthetic available radiation levels at the mat’s surface are very low due to the entrance’s orientation. Hobo dataloggers and a weather station now in the caves record temperature, relative humidity, and rainfall. Observations thus far suggest a significant fraction of available water in the caves comprises condensation from heated groundwater. The Bacterial community is not only extremely diverse, but it also contains a high degree of novelty. This diversity indicates the presence within the mat of complex microbial interactions (Ley et al., 2006). We have thus far identified over 54 Bacteria phylotypes from only 105 full length 16S rRNA gene sequences with 88% of these sharing <97% sequence identity with sequences (>1250 base pairs in length) in the public domain, a generally accepted indication of species level relationships. Furthermore 42% of these full length sequences share <95% identity, and 26% share <90% identity with any GenBank entry. In addition to the Bacterial lineages we have identified the presence of several highly divergent clades of nitrogen fixation genes homologues and Eucaryotic 18S rRNA gene sequences. Comparison to communities identified on surface lava from the caldera indicates subsets of the mat community are involved in interactions with the basalt substrates, whilst similarities to groups identified in the Guerrero Negro hypersaline microbial mat (Ley et. al. 2006) may indicate a natural community structure exists for cyanobacterial microbial mats.