The Bering Ecosystem Study (BEST) is a multi-year, interdisciplinary program to develop an end-to-end mechanistic understanding of how climate change will affect the marine ecosystems of the eastern Bering Sea, the continued use of their resources, and the social, economic and cultural sustainability of the people who depend on them. BEST is motivated by the realization that the Bering Sea is in the midst of significant, interrelated physical and biological change that may impact the region's carrying capacity and productivity, the sustainability of fish and shellfish stocks of great economic value for the nation, and the livelihoods of Native communities and fishers. These changes involve climate forcing, physical properties and processes in the ocean, and biological responses from the level of the physiology of individual organisms to the structure and function of entire ecosystems.