Archaeal Biomarkers in Antarctica

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Previously thought to inhabit only extreme environments, Archaea are now known to exist throughout the oceans. These prokaryotes can contribute over 34% of marine bacterioplankton biomass, thereby representing an important functional component of biogeochemical cycling in marine ecosystems. This Small Grant for Exploratory Research will investigate the relative importance of Archaea and Eubacteria in the Southern Ocean. Water column, sediment trap and sediment core samples will be analyzed to quantify archaeal and bacterial diversity and distribution. The presence of unique biomarkers for the lipid membranes of these two groups will be compared to results from molecular analyses with rRNA probes. The data obtained will also be used to evaluate the origin of archaeal signals in the benthos. Since archaeal lipids are relatively resistant to degradation, preservation in ancient sediments might be expected; but has not been observed. Instead, the concentrations of these compounds in sediments suggest in situ production rather than deposition from the water column. This project will provide important data for evaluating the relationship between water column and sedimentary archaeal biomarkers and for determining the origin of archaeal in benthic habitats. The combination of lipid biomarker analysis with molecular ecological probing to test these questions will establish an essential information base for future archaeal biomarker work in Antarctica.