The principal objective of the proposed research is to describe and explain how community composition and nutrient limitation of aquatic primary producers (especially algae) are influenced by land use and ecotonal complexity in the Andean Altiplano. The four large-scale nutrient flux treatments to be compared are: ancient raised fields currently under rehabilitation vs. flat pastures and fields (now more common), and complex littoral ecotones (shallow slopes) vs. simple ecotones (steeply sloping shorelines). Several hypotheses derived from the "big perturbation" of anthropogenic land-use changes are constructed as tests. Field sampling and measurements will take place in stream surface water between agricultural fields and the lake, and in nearshore zones of several drainage systems. Analyses will be primarily for the major forms of nitrogen and phosphorus, bioassay studies of nutrient limitation, and aquatic biological responses. Thus, nutrient-algal relations will be tested with both large-scale landscape treatments and more controlled bioassay experiments. These studies will be coordinated with ongoing field investigations by other scientists of: nutrient dynamics in agricultural fields, remote sensing and GIS-based modeling of land-water interactions, and archeological and paleolimnological studies of land use history.
