Epsilon Open Archive

Abstract

This thesis focuses on the assessment of spatial and temporal patterns of freshwater communities in relation to spatial variability and changes of the abiotic environment (i.e. water chemistry). The importance of geographic position, regional- and local-scale factors as drivers of the natural variability of lake and stream water chemistry was quantified and compared by variance partitioning using partial redundancy analysis. A major part of surface water chemistry was explained by interactions between geographic, regional and local factors. Streams and lakes were similar in their response, indicating that idiosyncrasies of both systems might be suppressed by effects of large-scale factors, in particular, if human-induced catchment variation generates a high amount of environmental noise. Regional processes are also important in structuring the composition of local communities. The relationship between local and regional diversity across three spatial scales and the importance of regional and local factors on macroinvertebrate diversity patterns was determined using the additive partitioning concept. Local processes (i.e. habitat heterogeneity) were an important factor contributing to species coexistence resulting in saturating patterns of the communities. On the other hand, local variability may confound the ability to detect perturbation or recovery. A multihabitat analysis of the rates and trajectories of recovery of acidified lakes as well as persistence of pelagic and benthic communities of acidified and reference lakes showed that recovery is a complex and challenging process, influenced by multiple spatial and temporal factors. For instance, climate-induced changes in surface runoff patterns may introduce significant variability in surface water chemistry confounding recovery and influencing the persistence and stability of freshwater communities. As focus is shifting from single-site to regional management of freshwater ecosystems, it is important that policy makers and managers are aware of which factors on which scale are most influencing water quality and biodiversity. The results of this thesis show that a holistic, multiscale analysis, involving several habitats and biotic indicators, is needed to understand ecosystem response to large-scale, regional stressors so as to best protect the world’s most precious and vital resource - freshwater.