Changes in fish isotopic signals: linking land use and reservoir food webs

Project no: 15-01625S

Principal investigator: Mgr. Mojmír Vašek, Ph.D.

Financial support: Czech Science Foundation

Duration: 2015–2017

This project aims to evaluate the impacts of anthropogenic nutrient subsidies on food web structure and functioning in reservoir ecosystems. Carbon and nitrogen isotope signals of key fish species will be measured in a representative sample of Czech reservoirs. The isotopic compositions of top consumers, combined with environmental monitoring data, will allow us to explore how the intensity of catchment land use affects food web dynamics, trophic interactions and energy flows in recipient reservoirs. Specifically, in this project a unique set of archived fish scales will be analysed for isotopic composition and the obtained results will be used to track historical changes in reservoir productivity and nutrient loading. We expect that changes in anthropogenic nutrient inputs can affect carbon cycling at the base of reservoir food webs and, consequently, these changes in carbon cycling are transferred to the top of food webs and reflected in isotope values of fish scales. Further, we intend to use a broad set of contemporary spatial data to examine whether reservoir fish community structure and fish scale isotope values reflect the intensity of catchment land use. We will compare reservoir catchments contrastingly influenced by human activities and we expect that the extent of human activities in catchments should significantly affect both community structure and isotopic composition of reservoir fishes. Finally, using both stable isotopes and traditional gut content analyses, we want to explore how trophic position and resource utilisation in reservoir fishes are influenced by anthropogenic nutrient subsidies and reservoir morphology. We expect that both anthropogenic nutrient inputs and reservoir morphology may have strong impacts on trophic niche differentiation in reservoir fishes. The project will provide novel results that improve our knowledge of functional links between aquatic ecosystems and surrounding landscapes, and can also help to formulate sound protection and management plans for freshwater catchments.