LIFE IN FRESHWATER HYDROTHERMAL VENTS

YELLOWSTONE LAKE
YELLOWSTONE NATIONAL PARK

For decades the colorful mats of bacteria and algae surrounding bubbling vents and fumaroles at Yellowstone National Park have been a focus of both touristic and scientific interest. It is with no small wonder that people look upon the growth of microorganisms in the often very hot, often very caustic fluids. Yet the interaction of biology with geothermal and geochemical energy may be more ancient than any other ecology. Prior to the mid-1970s, many scientists favored the theory of organic matter formation in the atmosphere and surface brine pools using lightning energy as the primary catalyst.

Following the discovery of deep-sea hydrothermal geo-ecosystems in the mid-1970s, an additional hypothesis was developed, invoking organic matter formation and biological assembly in the high-temperature (to 350 °C), high-pressure (>200 atm) deep-sea vents and surroundings. During the stabilization of early Earth hydrothermal systems would have started to be present after the surface of the planet had cooled enough to sustain liquid water. Evidence that hydrothermal systems also existed early in the history of Mars raises the possibility that life may have emerged on Mars as well. Both theoretical and experimental evidence supporting each theory exists, and in fact the two concepts are not mutually exclusive. These high temperature systems may thus be relevant to understanding extreme environments on Earth as well as other planets and moons in our Solar System.

boat on Yellowstone Lake Yellowstone Lake, WY is located in the caldera (85 x 45 km) of the largest volcanic eruptions known, which occurred 1.2M and 650,000 years ago at a mid-continental hot spot. The collapsed magma chamber now holds the northern half of Yellowstone Lake, while the Yellowstone River inflow and the southern half of the lake lie outside the caldera boundary. Within the caldera, geothermally heated water percolating through the relic chamber becomes enriched in carbonate, silicate, and chloride, with some locations additionally rich in methane, iron and sulfide. The park is world-renown for its geothermal activity. This provides a significant opportunity to delineate vent geochemistry effects on microbial community structure, activity, and distribution as well as bulk water composition, because enrichment occurs far from the most significant surface inflows. The northern half of Yellowstone Lake itself is strongly influenced by underwater geothermal hot springs and gas fumaroles. These features release waters with high concentrations of silicate and bicarbonate as well as reduced materials including hydrogen sulfide, Fe[II], methane, and more rarely ammonia into the bottom waters. In this respect, while the vents of Yellowstone Lake resemble deep sea hydrothermal systems in some important respects, the nearly closed nature of the basin and the relatively small volume of receiving waters provides additional opportunities for process research. Because riverine inputs and outputs may be estimated, Yellowstone Lake geothermal and biogeochemical activities are amenable to study oriented towards a mass balance approach.

Remotely Operated Vehicle photo Yellowstone National Park is well known for its steaming geysers, shimmering thermal pools and bubbling mudpots. Not as readily visible are the hydrothermal vents submerged under Yellowstone Lake (2-120m depth). As a result, use of a Remote Operated Vehicle (ROV) is critical for general survey and sampling hydrothermal vent systems in Yellowstone Lake. The ROV designer and operator Dave Lovalvo from Eastern Oceanics is a former Alvin and Jason pilot that has produced a practical array of modular instruments for water and solid phase sampling. With the Remotely Operated Vehicle (ROV) we are able to collect ventwater, surface sediment and solid-phase samples from different regions in the lake. New developments include a vent-o-rooter flexible sampling tube for deep throat water. This will allow us to sample vent fluids that have not entrained bottom water

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