Research Objectives:
Aquatic-terrestrial transition zones are crucial environments in understanding the biogeochemistry of landscapes. In temperate watersheds, these areas are generally dominated by riparian zones, which have been identified as biogeochemical “hot-spots” because of the increased microbial activity in these locations, and because of the importance of these hydrological margins in facilitating and buffering hydrologic and biogeochemical exchanges between terrestrial and aquatic ecosystems. In the antarctic Dry Valleys, terrestrial-aquatic transition zones are intriguing landscape features because of the vast importance of water in this polar desert, and because the material and energy budgets of dry valley ecosystems are linked by hydrology. Hydrological margins in aquatic-terrestrial transition zones (both lentic and lotic) will be studied to answer two overarching questions: 1) What are the major controls over hydrologic and biogeochemical exchange across aquatic-terrestrial transition zones? 2) To what extent do trends in nutrient cycling (e.g. nitrogen cycling) across these transition zones reflect differences in microbial communities or function vs. differences in the physical and chemical environment (e.g. redox potential)?
The hydrologic gradients that define these interfaces provide the opportunity to assess the relative influence of physical conditions (i.e. water availability, redox conditions), and microbial biodiversity and functioning upon biogeochemical cycling. Coordinated hydrologic, biogeochemical, and molecular microbial studies will be executed within hydrologic margins with the following research objectives:
+ Determine the role of sediment characteristics, permafrost and active layer dynamics, and topography on sub-surface water content and distribution in hydrologic margins,
+ Determine the extent to which transformations of nitrogen (N) in hydrological margins are influenced by physical conditions (i.e. moisture, redox potential and pH) or by the presence of specific microbial communities (e.g. denitrifiers), and
+ Characterize the microbial community structure and function of saturated zones.
Project team members will identify nine to ten study plots across aquatic-terrestrial transitions in the Dry Valleys, near streams and lakes. Researchers will sample each of these plots for soil water, nutrients, pH, and microbial communities to determine the diversity and hydrologic, biogeochemical, and microbial patterns in each aquatic-terrestrial transition location. They will also deploy data logging systems to acquire sub-surface soil temperature dynamics at three of these plots. Data will be collected throughout the austral winter and into the next austral spring/summer (2005).
