This open access book summarizes peer-reviewed articles and the abstracts of oral and poster presentations given during the YOUMARES 9 conference which took place in Oldenburg, Germany, in September 2018. The aims of this book are to summarize state-of-the-art knowledge in marine sciences and to inspire scientists of all career stages in the development of further research. These conferences are organized by and for young marine researchers. Qualified early-career researchers, who moderated topical sessions during the conference, contributed literature reviews on specific topics within their research field.

1. Science for the Future: The Use of Citizen Science in Marine Research and Conservation

2. A Literature Review on Stakeholder Participation in Coastal and Marine Fisheries
3. Law and Policy Dimensions of Ocean Governance
4. Status and Threats to Marine Biodiversity in the Anthropocene
5. Challenges in Marine Restoration Ecology: How Techniques, Assessment Metrics and Ecosystem Valuation can lead to Improved Restoration Success
6. Understanding how Microplastics Affect Marine Biota on the Cellular Level is Important for Assessing Ecosystem Function - A Review
7. Chemical Biodiversity and Bioactivities of Saponins in Echinodermata with an Emphasis on Sea Cucumbers (Holothuroidea)
8. Secondary Metabolites of Marine Microbes: From Natural Products Chemistry to Chemical Ecology
9. Sponges Revealed: A Synthesis of their Overlooked Ecological Functions within Aquatic Ecosystems
10. Theories, Vectors, and Computer Models - Marine Invasion Science in the Anthropocene
11. Benthos-Pelagos Interconnectivity: Antarctic Shelf Examples
12. Investigating the Land-Sea Transition Zone
13. Fisheries and Tourism: Social, Economic and Ecological Trade-offs in Coral Reef Systems
14. Progress in Microbial Ecology in Ice Covered Seas
15. Complex Interactions Between Aquatic Organisms and Their Chemical Environment Elucidated from Different Perspectives.