Abstract
Pelagic food web ecology has long been the major paradigm in the study of whole lake ecosystem dynamics. However, pelagic food webs might be highly influenced by benthic subsidies in which mobile fish may play a key role. The aim with this proposal is to examine the role of fish for coupling food web dynamics across habitats by focusing on the interaction between habitat productivity of resources and top-down control by piscivorous predators. We will do this using two different environmental gradients reflecting two types of disturbances in the environment: anthropogenic (total phosphorus) and climatic (dissolved organic carbon expected to increase in a warmer and wetter climate). We suggest a combined field study, experimental and modelling approach. 1) In the field we will first characterize habitat and habitat specific food web structure. Second, we will test the contribution of benthic secondary production for subsidizing top-down piscivorous predator control by using stabile isotope analyses. 2) We will then test an important mechanism for transferring of energy across habitats: the foraging rate of benthivorous predators in relation to turbidity and light. 3) Finally, we will use a simulation model to predict the importance of benthic subsidies for piscivorous foraging along the two gradients (tot-P and DOC). The results will be important for understanding how environmental disturbances will affect food web dynamics in lake ecosystems.
Sweden