We are organising an hybrid scientific session at the Ocean Science Meeting, 27 Feb - 4 March 2022 on ‘The uptake of data by citizen scientists, aggregators and end-users: successes, challenges and gaps in the dataflow’ and are inviting you to submit an abstract by 29 September 2021. Please find more details of the session below. OD11 The uptake of data by citizen scientists, aggregators and end-users: successes, challenges and gaps in the dataflow Keywords: Citizen science, marine data, dataflow, interoperability, acceptance, engagement, policy, data management, validation, end user needs, sustainability, impact Organizers: Patrick Gorringe, patrick.gorringe@smhi.se, James Sprinks, jsprinks@earthwatch.org.uk, Peter Thijsse, peter@maris.nl, Emilie Breviere, emilie.breviere@smhi.se Citizen science is a particularly impactful channel to collect data and its utility has been proven on small scales, yet the groundbreaking, and absolutely necessary, potential of citizen science has yet to be realized. Over the last decade, marine citizen science projects have provided a cost-effective means to collect extensive data sets covering vast spatio-temporal scales where conventional data collection is limited in operation, such as coastal seas. However many initiatives fail to be sustainable, and fail to reach acceptance of their data by scientists and by policy makers. To be efficient and successful a project should provide data with sufficient quality, structure and availability to be used by professionals and ensure that citizen scientists realize and appreciate the impact of their contribution towards the understanding of the scientific big picture. When studying the flow of citizen science data, it follows a series of steps from the providers to the users, via data aggregators. The essential steps of this process are the acquisition, management, flow in key infrastructure, evaluation and impact analyses, use in ocean models, research and forecasting, and public visualization. The objective of the co-organizers is to provide a session during which participants will share experiences on successes and failures, needs and limitations in the data flow chain. The session wishes to be a unique niche for the numerous actors of the data flow in marine citizen science initiatives to meet and exchange. It will explore current and future collaborations, hear from invited experts about wider citizen science initiatives and discuss how marine data aggregators in its next phase can more systematically link with citizen science to not only expand the data provision from citizen science, but also find ways to encourage citizen science to work closer with data aggregators across the full value chain.