Liming has been used extensively in Sweden, but the management success has been only partial, mostly mitigating the impact of acidification rather than restoring the ecological communities to a self-maintaining pre-acidified state. Rather than a sound restoration tool, liming is a form of command-and-control management that comprises a significant disturbance in the system, which manifests in the form of profound alterations of biophysical settings of lakes. This thesis aims to assess biological responses to liming with a special focus on resilience by looking at the cross-scale interaction aspects of littoral invertebrate communities in limed lakes within the framework of panarchy theory. The thesis is based on multivariate time series modeling (AEM-RDA) to extract hierarchical temporal fluctuations patterns (temporal scales) in littoral invertebrate communities. This analysis tested for the premise of panarchy theory that complex systems are hierarchically structured. Time series analyses were followed by Spearman rank correlation analysis to test another premise of panarchy theory; namely, that “information” (e.g., management interventions) flows between these hierarchical scales. Specifically, Ca:Mg ratios were used as a surrogate of liming, and correlated with each temporal pattern identified by the AEM-RDA. The result showed the distinct temporal scales in littoral invertebrate communities in limed lakes, fitting the premises of panarchy theory and agreeing with previous studies that found hierarchical temporal organizations in other lake communities. The correlation analyses indicated weak cross-scale manifestation of Ca:Mg ratios in the littoral invertebrate communities, suggesting a weak information flow of liming in managed lakes. This “dilution” of management may provide one mechanism that could explain why liming is not effective in creating a self-organizing, resilient system. The results of this study allow shedding further light on liming as a coerced regime (degraded complex systems forced into a state of desired conditions (e.g., ecosystem service provisioning) through constant management). Most research has so far focused on the evaluation of traditional metrics of biodiversity, which have shown that community structure is substantially altered in limed lakes, deviating from those in circumneutral reference lakes and degraded acidified lakes. This thesis, therefore, concludes that integration of traditional ecological approaches and complexity studies may provide complementary insight into the organization of ecosystems and sustainable resource management.

Cross-boundary movements of energy and material are ubiquitous. Freshwater ecosystems receive nutrients, dissolved, and particulate organic matter from adjacent terrestrial ecosystems, whereas terrestrial ecosystems mainly receive prey organisms and detritus deposited by physical processes such as floods from freshwater ecosystems. Within lakes, fish are considered as integrators between habitats due to their high mobility, although they often occupy either near-shore littoral or open-water pelagic habitats and develop habitat-specific morphologies. Such intra-population divergence in morphological traits might limit the use of multiple habitats. In this thesis, I first focused on quantity and quality of reciprocal fluxes of particulate organic matter between freshwater and terrestrial ecosystems and responses of recipient consumers. Freshwater ecosystems generally received higher amounts of externally-produced resources than terrestrial ecosystems. Despite this discrepancy, aquatic and terrestrial consumer responses were similar, likely due to the differences in resource quality. Second, I investigated the potential of particulate organic carbon (POC) supporting benthic food webs in lakes; a pathway that has largely been neglected in previous studies. I found that POC can substantially subsidize the benthic food web and that the effects on the benthic food web were transferred to the pelagic habitat, thus emphasizing the importance of benthic pathways for pelagic production. Third, I examined how water transparency can affect intra-population divergence in perch (Perca fluviatilis). I observed that increased water transparency can considerably increase morphological divergence between littoral and pelagic populations likely due to its effects on foraging. Finally, I investigated the effects of such intra-population divergence on littoral-pelagic food web coupling. I found that low morphological divergence corresponded with high overlap in resource use, whereas strong morphological divergence resulted in low overlap in resource use. Here littoral populations mainly utilized littoral resources and pelagic populations primarily utilized pelagic resources, indicating that habitat coupling might be strongly limited when intra-population divergence is high. In conclusion, although different ecosystems seem separated by distinct physical boundaries, these boundaries are often crossed. However, the development of habitat-specific adaptive traits might limit movement between apparently contiguous habitats.