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Mono Lake Microbial Observatory Study Area

Mono Lake is a closed-basin, alkaline, hypersaline lake located at the western edge of the Great Basin in eastern California. Saline lakes and similar alkaline, hypersaline environments are widespread today and have been important features of the hydrosphere since the earliest stages of the formation of the Earth's oceans (Kempe, 1985).

Map of Mono Lake showing Microbial Observatory sampling stations
(Depths are relative to a lake surface elevation of 1946 m)

Mono Lake sampling stations

Solar heating causes thermal stratification, leading to seasonal bottom water anoxia. Saline lakes are prone to longer periods of anoxia resulting from salinity stratification driven by interannual variation in local hydrology that prevents complete overturn and ventilation of the water column during winter, allowing reduced species, especially sulfide, ammonia and methane, to accumulate to high concentrations (Jellison, 1993). Mono Lake last mixed completely in 1995, but mixed partially last winter and is likely to mix completely this fall, completely oxygenating the bottom water and surficial sediments in the deepest parts of the lake for the first time in 8 years (see report).

Mono Lake's chemistry and ecology are similar to numerous other saline lakes in the Western US, including lakes that are undergoing salinization as a result of freshwater withdrawal to support agriculture (for example Pyramid and Walker Lakes in Nevada, but there are numerous examples world-wide, one of the more spectacular being the former Aral Sea (Micklin, 1988). Wetlands or reservoirs that receive agricultural drainage water (for example Kesterson National Wildlife Refuge in California or the Carson Sink in Nevada) also have similar chemical and microbiological characteristics (Presser, 1984; Presser, 1985; Oremland, 1989; de Souza, 2001).

References Cited

de Souza, M.P., Amini, A., Dojka, M.A., Pickering, I.J., Dawson, S.C., Pace, N.R., and Terry, N. (2001) Identification and characterization of bacteria in a selenium contaminated hypersaline evaporation pond. Applied and Environmental
Microbiology 67: 3785-3794.

Jellison, R., and Melack, J.M. (1993b) Meromixis in hypersaline Mono Lake, California. 1. Stratification and vertical mixing during the onset, persistence, and breakdown of meromixis. Limnology and Oceanography 38: 1008-1019.

Kempe, S., and Degens, E.T. (1985) An early soda ocean? Chemical Geology 53: 95-108.

Micklin, P.P. (1988) Desiccation of the Aral Sea: a water management disaster in the Soviet Union. Science 241: 1170-1176.

Oremland, R.S., Hollibaugh, J.T., Maest, A.L., Presser, T.S., Miller, L.G., and Culbertson, C.W. (1989) Selenate reduction to elemental selenium by anaerobic bacteria in sediments and in culture: biogeochemical significance of a novel, sulfate-
independent respiration. Applied and Environmental Microbiology 55: 2333-2343.

Presser, T.C., and Barnes, I. (1984) Selenium concentrations in waters tributary to and in the vicinity of the Kesterson National Wildlife Refuge, Fresno and Merced counties, California. In. Menlo Park, CA: U.S. Geological Survey, p. 45.

Presser, T.C., and Barnes, I. (1985) Dissolved constituents including selenium in waters in the vicinity of Kesterson National Wildlife Refuge and the west grassland, Fresno and Merced counties, California. In. Menlo Park, CA: U.S. Geological Survey, p. 89.


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	This material is based upon work supported by the National Science Foundation under grants MCB 99-77886, MCB 99-77892, and MCB 99-77901. Any opinions, findings, conclusions, or recommendations expressed in the material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.