Collaborative Research: Evolution Of Environments Within Black Smoker Chimney Walls: Microbial Colonization As Functions Of Temperature, Chemistry, And Time

Portland State University, Portland OR

Investigators

Abstract

The researchers will investigate the interaction of microorganisms with their geochernical environment in chimney deposits that are actively forming in the Guaymas Basin hydrothermal system. The specific objectives of this study are twofold. First, they will trace the evolution of the thermal/chemical/physical environment within newly formed chimney walls over time-scales of minutes to months and determine the distribution of microorganisms within this temporal/chemical/thermal/spatiaI framework. Second, they will assess subsurface geochemical processes responsible for the delivery of organic and inorganic metabolic energy sources and nutrients from deep-seated reaction zones to near seafloor environments. These goals will be attained by identifying microbial populations that inhabit well-constrained temperature and compositional domains within the walls of newly formed and existing chimneys through a collaborative and interdisciplinary study with Drs. Debra Stakes (MBARI), Randy Koski (USGS), and Geoff Wheat (University of Alaska Fairbanks-MBARI campus), using the MBARI RN Western Flyer and ROV Tiburon. Temperature within the walls of newly formed chimneys will be monitored using thermocouple arrays that are enveloped during chimney growth. The new chimneys will subsequently be recovered and the solid material in the immediate vicinity of each thermocouple used for enrichment cultures, molecular phylogenetic approaches, and fluorescent in situ hybridization with 16S rRNA-specific probes, while splits of the same material will be fully characterized with respect to their mineralogic, chemical, and isotopic composition. Vent fluids delivering nutrients and chemical energy from deep-seated subsurface reaction zones to the seafloor will be analyzed using a comprehensive analytical plan that involves quantitative determination of the abundance of aqueous organic, inorganic, and gaseous species. Compositional data for fluids and solids will be used to constrain thermodynamic and diffusive-advective models that allow estimation of fluid composition and temperature within chimney walls, information that will facilitate calculation of the amounts and sources of chemical energy available for metabolic activity. Mineralogical, chemical, and isotopic analyses of chimney minerals will provide key information on conditions present as the chimneys have evolved that can be compared to the thermal history as recorded by the thermocouples, and to the results of model calculations. The resultant understanding of the time dependent colonization of chimney environments in which the P-T-X conditions are known will address important questions about how microorganisms grow in these extreme environments, and what the geochemical constraints are on microbial diversity and succession. The methods the investigators will use have all been applied successfully at other vent sites. What makes this research unique is the combination of these technologies and interdisciplinary expertise to assess biogeochemical processes within vent environments.