Faculty of Biology
Aquatic Ecology
Universitätsstrasse 5
D-45141 Essen

PhD thesis: Delineating multiple stressor-response relationships at the individual level:
A mechanistic modelling approach

The goal of my PhD thesis is to model the causal chain of effects from multiple stressors to environmental variables to organisms in stream ecosystems. The model will be mechanistic and operates on the individual level. It is part of the DFG-funded collaborative research center CRC 1439 “Multilevel response to stressor increase and release in stream ecosystems” (RESIST).

The model will simulate binary combinations of the stressors temperature increase, salinisation, and hydromorphological modifications. These stressors influence environmental variables like dissolved oxygen (DO), dissolved organic carbon (DOC) and electrical conductivity (EC) as well as organisms (microorganisms, microphytobenthos, parasites, invertebrates, and fish). The environmental variables also interact with each other and affect the organisms. The stressors can affect the organisms directly or indirectly through the environmental variables. The organisms are classified by body size and environmental effects on them are calculated in relation to these size classes. Depending on the size we expect direct or indirect effects of the stressors to be more prevalent.

The model will increase the understanding of stressor-response mechanisms and help predict responses of organisms in streams to multiple stressors. In further steps biotic interactions can be added to elevate the model from the individual level to the community level.