Freshwater food web structure

Species traits nutrients, food web structure and energetics in freshwater ecosystems

This research programme studies key processes that affect the functioning of aquatic ecosystems, such as nutrient input and nutrient cycling between land and water. We quantify the main matter and energy flows in freshwater ecosystems and elucidate how nutrient fluxes integrate with biological and biochemical dynamics. We determine how predator-prey interactions involving top predators (i.e., fishes in reservoirs and predatory macroinvertebrates in smaller fishless waters) affect, via top-down effects, trophic cascades and potential ecological regime shifts. We follow direct and indirect impacts of anthropogenic stress on individuals, populations and communities through (i) alterations in habitat and niche use and (ii) changes in individual behaviour and physiology. Main focus is put on the measurement of functional dependencies in freshwater ecosystems by combining laboratory experiments, mesocosm arrays and in situ studies, with emphasis on ecosystems under anthropogenic stress.

Key question

How do resource flows in aquatic food webs affect the functioning of aquatic ecosystems? How do changes in resource flows alter direct and indirect species interactions? What are the key underlying mechanisms?


To gain detailed, complex understanding of the effects of abiotic stressors on biotic interactions in freshwater ecosystems, we survey food webs across the entire body size continuum from bacteria and phytoplankton to fish using mesocosm experiments and long-term monitoring of all trophic levels using methods operating on various spatial scales. Small-scale processes will be studied

at the newly built mesocosm facility at the USB, allowing for controlled conditions and joint manipulation of multiple abiotic conditions in fully factorial experimental designs. Behavioural responses to anthropogenic stressors are studied primarily in macroinvertebrates using newly acquired laboratory equipment at the USB. Large-scale interactions are studied in lakes and riverine reservoirs with naturally present environmental gradients.