Structure and dynamic of food webs in Andean North Patagonian freshwater systems: organic matter, light and nutrient relationships

north andean patagonian aquatic systems include a number of deep and shallow oligotrophic lakes with a profuse hydrographic net. in this contribution we present a review of the researches carried out during the last decade in the food webs of north patagonian water bodies. food webs in these systems were studied based on field surveys, combining with field and laboratory experiments. deep and shallow lakes were analyzed in relation to light, organic matter, and nutrient constraints as limiting interacting factors. in addition, we have also extended our knowledge on the structure and dynamics of stream food webs by analyzing different aspects of biotic interactions occurring both through the autotrophic and heterotrophic pathways. since andean lakes were defined as high-light low-nutrient environments, and in this scenario high c:p ratios would be expected, food webs of these lakes may be characterized by low food quality for herbivores. we analyzed how this low food quality affects the distribution of zooplankters, and the response at the cellular level. in shallow lakes, macrophytes contributed substantially to the dissolved organic matter content. also the littoral zone offers higher food availability and refuge against predation. finally, we analyzed the impact of the introduction of exotic salmonids on food webs of shallow lakes and headwater streams.