Other
Scientific paper
Dec 2004
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004agufmos42a..05k&link_type=abstract
American Geophysical Union, Fall Meeting 2004, abstract #OS42A-05
Other
4832 Hydrothermal Systems, 4200 Oceanography: General, 4294 Instruments And Techniques
Scientific paper
Determining the maximum conditions under which life thrives, survives, and expires is critical to understanding how and where life might have evolved on our planet and for investigation of life in extraterrestrial environments. Submarine black smoker systems are optimal sites to study such questions because thermal gradients are extreme and accessible within the chimney walls under high-pressure conditions. Intact cells containing DNA and ribosomes have been observed even within the most extreme environments of sulfide structure walls bounded by 300\deg C fluids. Membrane lipids from archaea have been detected in sulfide flanges and chimneys where temperatures are believed to be 200-300\deg C. However, a balanced inquiry into the limits of life must focus on characterization of the actual conditions in a given system that favor reactions necessary to initiate and/or sustain life. At present, in-situ instrumentation of sulfide deposits is the only effective way to gain direct access to these natural high-temperature environments for documentation and experimentation. With this goal in mind, three prototype microbial incubators were developed with funding from the NSF, University of Washington, and the W.M. Keck Foundation. The incubators were deployed in 2003 in the walls of active black smoker chimneys in the Mothra Hydrothermal Field, Endeavour Segment of the Juan de Fuca Ridge. All instruments were successfully recovered in 2004, and one was redeployed for a short time-series experiment. Each 53-cm-long titanium assembly houses 27 temperature sensors that record temperatures from 0 to 500\deg C within three discrete incubation chambers. Data are logged in a separate housing and inductively coupled links provide access to the data loggers without removal of the instruments. During the initial deployment, data were collected from 189 to 245 days, with up to ˜478° K temperature measurements completed for an individual instrument. Temperatures within the chimney walls ranged from near ambient conditions to ˜280° C. Distinct thermal gradients were delineated extremely well in each of the three discrete environmental chambers in all instruments. In one instrument numerous perturbations were recorded simultaneously on all 27 probes showing temperature increases of up to ˜30° C. Smaller-scale fluctuations resulting from tidal perturbations were ubiquitous in all instruments. Tidal pumping that mixes oxygenated seawater and reduced, volatile-rich hydrothermal fluids may be critical for development of dense and diverse microbial communities within the outer chimney walls. Preliminary examination of some sterile mineral surfaces emplaced within the chambers shows extensive biofilm development. Culturing experiments are ongoing and DNA has been successfully extracted from many of the chambers for genetic characterization. This experiment is a component of the W.M. Keck Foundation-funded proto-NEPTUNE Observatory and Ridge R2K program at Endeavour.
Baross John
Delaney Jeremy
Girguis P.
Kelley Dan
Schrenk Matthew
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