THE PRESENCE AND POTENTIAL IMPACT OF GEOTHERMAL ACTIVITY ON THE 

 CHEMISTRY AND BIOLOGY OF YELLOWSTONE LAKE, WYOMING 



J. Val Klump 1 ' 2 , Charles C. Remsen 1 , and Jerry L. Kaster 1 



Center for Great Lakes Studies 



-'-Department of Biological Sciences 



^Department of Geological and Geophysical Sciences 



University of Wisconsin—Milwaukee 



Milwaukee, WI 53201 



ABSTRACT 



Yellowstone Lake, Wyoming is located in a tectonic "hot 

 spot" and lies within the Yellowstone caldera, a region with some 

 of the highest measured geothermal heat fluxes in the world. 

 Geothermal gradients within the lake bed are consequently very 

 high and hydrothermal springs and hot gas fumaroles occur within 

 the lake itself. These features are unique in limnology and 

 indications are that they may have a significant impact on the 

 chemistry, nutrient dynamics and biology of this oligotrophic 

 system. Observations to date have revealed nearshore regions 

 with widespread gas ebullition, numerous small springs or seeps, 

 and elevated (95° C) substrate temperatures. Gases are primarily 

 carbon dioxide, with traces of methane and hydrogen sulfide. 

 Hydrothermal waters reaching 70° C are anoxic and high in 

 dissolved nutrients. Enhanced biological activity surrounds 

 these vents with mats of microbial heterotrophs and photo- and 

 chemo-lithotrophs, hydroponic-like algal growth and dense 

 congregations of aquatic worms. Geophysical evidence indicates 

 that hydrothermal activity may be widespread. ROV observations 

 demonstrated directly that geothermal activity was present in 

 the deepest areas of the lake as well as in the shallow 

 nearshore zones. 



INTRODUCTION 



The Yellowstone System 



Yellowstone Lake (Fig. 1), the largest high altitude lake 

 in North America, is situated in Yellowstone National Park, one 

 of the most tectonically active regions in the world. Like the 

 Hawaiian Islands, Yellowstone represents a hot spot in the 

 earth's crust. The Yellowstone plateau, with an average 

 elevation of ~ 2000 meters, overlies magma chambers which are 

 the source of heat for the well known geothermal features in the 

 Park: geysers, hot springs, fumaroles, and mud pots. 



Over the last 2 million years, there have been 3 major 

 volcanic episodes in Yellowstone (Christiansen and Blank 1972). 



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