An international research project known as Biological Investigations of Marine Antarctic Systems and Stocks or BIOMASS was a unique, 15-year, international research program established to investigate the ecology of the Southern Ocean. This volume summarizes the results of this monumental research effort and provides a succinct, state-of-the-art account of the ecology of the Southern Ocean, covering the physical marine environment, marine stocks (phytoplankton, zooplankton, krill, fish, and birds), marine systems, and future research endeavors.