Project SYMBIOSES delivers a fully operational modeling system that performs combined ecological and ecotoxicology simulations of the marine ecosystem. The project aim is to provide more quantitative information on the risks and benefits of petroleum de velopment in a given region. Our test area will be for the Barents Sea/Lofoten region with initial focus on the simultaneous effects of fisheries and petroleum activities on fish and plankton communities. This is an area where sufficient baseline data and scientific knowledge exists. In principle, this integrated modeling framework may be adapted for use in other marine areas. The model system proposed here will add more value to ecological risk assessment by allowing exploration of possible outcomes of a range of risk scenarios. This integrated modeling system further provides a framework to synthesize and organise knowledge acquisition activities and thereby improve the identification of knowledge gaps requiring future financing. The main features of the modeling system are:- An integrated modeling framework located on the Norwegian national supercomputer facility - Individual models connected to the framework: adult fish, fish eggs & juveniles, phyto- and zoo- plankton, chemical fate and ecotoxicol ogy- Realistic predictions with quantification of uncertainty - A management tool for spatial/temporal planning and risk reduction - An impact and risk calculation tool to support go/no-go decisionsThis new modeling system is expected to become an es sential aid to ecosystem-based management, decision-making and stakeholder communication for spatially managed areas.