Project: A Lost City-type hydrothermal system in readily accessible, shallow water

The Strytan Hydrothermal Field (SHF; Eyjafjord, northern Iceland) exhibits alkaline (pH ~ 10), hot (up to 78 degrees C), submarine hydrothermal venting, resulting in the formation of numerous saponite towers. We performed a detailed geochemical and microbiological characterization of hydrothermal fluids and precipitates from the site. End-member calculations revealed elevated concentrations of many major and trace elements (e.g., 2.4 mM Na, 3 to 27 uM K, 40 to 120 uM Ca, 10 to 25 uM B, and overall high concentrations of trace elements). We hypothesize that recharge of meteoric water occurs in the mountains south of Eyjafjord, and low temperature alteration of plagioclase, pyroxene and olivine in basalt, and precipitation of calcite, occurs in a closed system. This explains the observed high pH, variable Ca concentrations, and low DIC. CH4, H2, and CO concentrations were all elevated relative to normal seawater (up to 1.41, 5.19, and 0.13 uM, respectively), and a range of δ13C-CH4 was measured. Weathering of pyroxene may produce H2, which combines with CO2 to form abiotic CH4. The abiotic production of H2 and CH4 in a site such as the SHF broadens the range of potential origin of life environments significantly. Intact polar lipids indicate Bacteria dominated all samples except one. Up to 50% of the lipids at this site were archaeal. Bacterial clone sequences were dominated by betaproteobacteria (Dechloromonas sp.), followed by deltaproteobacteria (Desulfovibrio sp.) Archaeal results indicate a dominance of Crenarchaeota, particularly Thermoproteales, followed by Desulfurococcales. More detailed analysis of microbial communities is currently underway.