Large volumes of produced water are generated and discharged to the coastal and ocean waters worldwide from offshore oil and gas production facilities. There is concern that the chemicals in the produced water may harm marine ecosystems. This book summarizes the bioavailability and marine ecotoxicology of metal and organic contaminants that may occur in oil well produced water at concentrations significantly higher than those in ambient seawater. The contaminants of concern include arsenic, barium, cadmium, chromium, copper, lead, mercury, radium isotopes, zinc, monocyclic aromatic hydrocarbons, polycyclic aromatic hydrocarbons, phenols, and bis(2-ethylhexyl)phthalate. The first part of the book is a detailed discussion of the chemical composition of produced water from offshore oil wells worldwide and its fates following discharge to the ocean. The remaining chapters of the book summarize the current scientific literature on the sources and distributions in the ocean of each of the contaminants of concern and their bioaccumulation and toxicity to marine organisms. The book advances the concept that bioavailability evaluation must be included in all ecological risk assessments and other environmental assessments of chemical contaminants in marine and freshwater ecosystems.