Offshore wind farm development is a is a highly complex process. The societal and political pressure to implement is high while environmental responses and future developments in the global energy network are uncertain. Moreover, many interests in maritime space are at stake. The dependency on knowledge for decision-making is high, but the capacity to use knowledge is limited. In this paper we investigate the role of ecosystem knowledge in offshore wind farm planning and management. We have identified 4 types of research arenas: (1) government driven (e.g., monitoring programs) (2) subsidized research (national or EU), (3) industrial or PPS (Public-private partnerships), and (4) research by universities. This study considers the way in which knowledge from different arenas is or could be taken up and used in policy. We identify that particularly government-driven research (monitoring) is used in policymaking. The analysis of policy documents, in-depth expert interviews and focus groups reveals that the distance between knowledge developers and knowledge users may differentiate from purely transactional relations to co-production-relations. However, co-production is rare beyond the monitoring programs directly initiated by the government agencies.