The marine food web is at the centre of both the climate-related CO2 cycle and food production in the marine environment. It plays a key role in regulating the climate system and is highly sensitive to climate change and other stressors. OCEAN-CERTAIN will investigate the impact of climatic and non climatic stressors on the food web and the connected biological pump, and the important feedback mechanisms. OCEAN-CERTAIN will identify and quantify multi-stressor impacts and feedbacks and how these alter the functionality and structure of the food web and efficiency of the biological pump in different bio-geographical regions. This will be done by utilizing existing ecosystem models employing existing data, in addition to mesocosm, lab-scale experiments and field study. The resulting knowledge will then be used to assess socio-economic vulnerabilities and adaptive capacity by using indicators of food-web functions as responses to particular changes by way of stressor combinations. OCEAN-CERTAIN will then address socio-economic policy and management issues by using highly interactive participatory stakeholder workshops to create models of user group resilience and adaptability. These will show how potential climate-driven physical, chemical and biological changes may affect relevant economic activities and human welfare and help to identify adaptation pathways. This information and knowledge will reduce of epistemic uncertainty and help policy makers chose among management options, which in turn will be treated as additional feedbacks to the food web. The stressors, key feedback mechanisms and indicators, form the basis for the design of an integrated Decision Support System (DSS).