Importance of fish community structure, nutrients and browning for shallow lake ecosystem dynamics : A modelling perspective

Sammanfattning: In a changing climate, it is increasingly important to be able to model environmental effects on food webs, and to do that, one must have appropriate dynamic models. I present a shallow lake ecosystem model where producers, grazers, carnivores, piscivores, and detritivores are coupled through resource (light, nutrients and detritus) fluxes between the benthic and pelagic habitats and through carnivore life history events (ontogenetic habitat and diet shifts). The two habitats each contain primary producers, grazers, carnivores and detritivores. Within the habitats, there is strong top-down regulation, but across habitat boundaries, bottom-up interactions drive production. In the absence of piscivores, stage-structured carnivores cause intriguing patters of alternative stable states. Notably, the model predicts a lesser dependence on benthic production with detritus presence. Model predictions are largely in agreement with empirical studies. The results have implications for management of freshwater, and for the interpretation of previous models.