It is important for humans to understand how ecosystems work because we depend on them for a variety of products and services. For example, rivers and streams provide fisheries, improved water quality, and recreational opportunities to many individuals. In rivers, interactions among fishes, other stream plants and animals, and the physical river environment can influence continued provision of these valuable services. However, the role played by many freshwater fishes in the provision of these services remains unknown. Additionally, it is important to identify different factors that affect the outcome of interactions involving riverine fishes. To address these issues, I evaluated how fishes influence different properties of rivers and streams, using a combined approach that summarized previous studies of fish effects on trophic structure and organic matter processing and incorporated field work in natural systems. Overall, my work demonstrated that fishes can play important roles in rivers and streams. In particular, fish spawning migrations from lakes to streams can introduce nutrients to streams. Compared with other nutrient sources for streams, nutrients delivered by fish migrations can be substantial, and they may be used by other plants and animals in the stream to increase productivity. Beyond nutrient introduction, the physical disturbance of river sediments caused by the spawning activity of large migratory fishes can influence the availability of food resources for other stream animals. Additionally, my summary of previous fish studies indicated the consistent influence of fishes on nutrient dynamics and other stream organisms. While the role of riverine fishes varies, natural resource managers and researchers should focus on understanding how these widespread organisms influence valuable ecosystem services derived from freshwater resources.

Purpose - The purpose of this thesis is to advance the understanding of risk exposure and management for different roles in business ecosystems. The following research questions have been derived to fulfill this purpose: RQ1: Which risks are different business ecosystem roles exposed to, and in what way? RQ2: How can business ecosystem actors mitigate risks? Method – A single case study has been conducted on a business ecosystem surrounding the development of autonomous cars in the EU. An abductive and qualitative approach has been applied, which allowed the combination of existing literature and new empirical findings as to the foundation for building new theory. Data was collected through 21 semi-structured interviews and analyzed through comparison between codes on risks, roles, and risk mitigation strategies. Findings – The already existing literature on business ecosystem risks was confirmed and nuanced. On top of this, two new risks were found, disintermediation risk (the risk of being fully or partially excluded from the ecosystem) and accountability risk (the risk of being responsible for other business ecosystem actors output to a third party). The findings also declare that risks vary between actors, but also due to other factors such as investment in the ecosystem and an actor's relative size to other actors. Finally, suggested risk response strategies for each risk were derived. Theoretical implications - We have contributed to the literature on risks within business ecosystems by adding two new risks: disintermediation risk and accountability risk. We have also contributed to the overall literature on business ecosystems by combining the two sub-streams risks in business ecosystems and roles in business ecosystems. In addition to the theoretical implications for the business ecosystem literature, we have contributed to the risk management literature by applying it in the new context of business ecosystemsto extend the applicability of the risk management literature. Practical implications - Our findings shed light on how risks are distributed between different roles and can therefore provide guidance in this issue. The current study also contributes to the understanding of how risks vary with respect to other factors than roles, which could be valuable knowledge for managers. Finally, practical guidance on how risks can be mitigated is presented which is valuable for any actor in a Business ecosystem.