Global ETD Search

1	Importance of fish community structure, nutrients and browning for shallow lake ecosystem dynamics : A modelling perspective Karlberg, Ylva January 2019 (has links) 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. biological modelling bowning food webs trophic interactions top-down and bottom-up control nutrients light shallow lake biologisk modellering brunifiering födovävar trofiska interaktioner näring ljus grund sjö Ecology Ekologi
2	The influence of northern pike on the diet of Eurasian perch Ylva, Karlberg January 2017 (has links) Top predators in aquatic ecosystems often have strong top-down effects on the ecosystem. Northern pike (Esox lucius) has been documented to cause whitefish (Coregonus lavaretus) populations to diverge into different ecomorphs. This can facilitate piscivory in other predators as a novel resource becomes available to them in the form of dwarf whitefish. The aim of this study is to examine whether the presence of pike causes Eurasian perch (Perca fluviatilis) to shift their diet from insectivory to piscivory, and whether this is directly driven by whitefish polymorphism. Stomach contents of 147 perch from lakes with and without pikes were analyzed. The results show that the presence of pike has a clear influence on the diet of the perch. In lakes without pike, perch are mostly insectivorous, and in lakes with pike, they are mostly piscivorous. This diet shift appears to be driven by whitefish availability, as a majority of the diet of perch in pike lakes consisted of whitefish, while none of the fish eaten by perch in non-pike lakes was whitefish. In addition, the results showed that perch undergo the diet shift from insectivory to piscivory at a smaller size when coexisting with pike. This study can be added to the growing body of evidence for the ecological significance of pike. Perca fluviatilis Esox lucius Coregonus lavaretus trophic interactions facilitation Eurasian perch northern pike whitefish Perca fluviatilis Esox lucius Coregonus lavaretus trofiska interaktioner facilitering abborre gädda sik Ecology Ekologi

Search results

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

The influence of northern pike on the diet of Eurasian perch