Lake ecosystems in temperate zones are influenced both by seasonally-varying external forces and by internal biogeochemical cycling; however, hydrologic mixing and dilution may obscure the importance of some biogeochemical processes. In contrast, lakes in the Dry Valleys of Antarctica are influenced by a seasonality that is simple in the extreme, are stabilized by a permanent ice cover, and receive proportionately minor annual inputs of chemical constituents, including organic material and nutrients, from glacial meltwater streams. Therefore, these lakes are uniquely suited for the study of processes involved in the internal production and degradation of organic material. This study will focus on the chemical and biological changes occurring during the austral winter (constant darkness) and the austral summer (constant daylight) and on the interaction or feedback mechanisms between processes occurring in major zone of these lakes. The study will be accomplished by measuring key autotrophic and heterotrophic processes and related chemical parameters, by quantifying lake hydrology and by deploying sampling devices to operate during the winter. Knowledge of these lake ecosystems will enhance our understanding of internal biogeochemical cycling in other lakes.
