Marine polar ecosystems are often claimed being sensitive and having low tolerance toward external stress. In the Norwegian sector of the Barents Sea, this assumption has caused the implementation of a zero physical discharge policy. This policy is preventing an empirical definition of tolerance limits in relation to petroleum activities and the application of tailored and effective mitigation measures. Eni E&P, its subsidiary Eni Norge, TOTAL E&P and its subsidiary TOTAL E&P NORGE, have launched the BIOSEA JIP in cooperation with IRIS-Biomiljø. The aim of the project was to build a scientific platform for risk based environmental management of Arctic E&P offshore activities. The BIOSEA initiative, developed over a 6 years period, aimed at establishing a suitable set of tools for environmental monitoring in offshore areas, and at adding knowledge on the sensitivity of Arctic species to dispersed crude oil and produced water. The project finished in December 2009 and the main achievements are presented in this paper. Controlled laboratory exposure experiments and on site field surveys clearly demonstrated the relevance of typical oil exposure parameters (biomarkers) as valuable tools for oil exposure monitoring in different Arctic species. The monitoring toolbox was refined based on sensitivity and response patterns of individual biomarkers. Biomarker field reference levels were also established for the same species, as some biomarkers may be influenced by environmental and seasonal conditions. Based on data obtained from laboratory exposure experiments and field baseline monitoring, biomarker threshold levels were estimated. By establishing such biomarker threshold levels, BIOSEA has significantly contributed to the definition of assessment criteria to be used for monitoring of the environmental quality in the marine environment, as required by the Integrated Management Plan for the Barents Sea and Lofoten areas.