P182-TU MOLECULAR CHARACTERISTICS OF MICROBIAL MATS FROM WARNER VALLEY, OREGON: FORMATION OF WAX ESTERS DURING DESSICATION

caused by seasonal- to decadal-scale droughts. They are fed by springs of varied temperature (9- 71°C) and pH (6.5-8.3), typically originating from fractures within Oligocene basalt, are HCO3- dominated, and support microbial mats. From late spring through summer the lake waters are concentrated by evaporation, which produces wide variations in their chemistry and thermal structure from the interplay of supply/evaporation. Water chemistries range from moderately to highly alkaline to sulfate-chloride dominated, and vary widely in pH (8.3-10.5) and total dissolved solids (TDS; 25-300,000 ppm). Throughout the system, microbial mats in the lakes, playas, and springs are controlled by temperature (psychrophiles, mesophiles, thermophiles, and hyperthermophiles) and chemistry (alkalophiles and halophiles), and are augmented by seasonally dynamic microbial populations that respond to profound shifts in temperature, pH and ion and metal concentrations. The production and abundance of wax esters is enhanced in microbial mats undergoing desiccation compared to equivalent hydrated mats. Wax esters are markedly lower in abundance (~18 g/g C) among the lipids from live mats in alkaline waters (average alkalinity = 122 mg/l as total CaCO3, pH = 9.1-10.5, TDS = 237 ppm; temperature = 19.6°C)