Many previous studies and books have been dedicated to fundamental and developmental aspects of biomarkers. The purpose of this book is to provide, through various case studies, an overview of the practical use of biological markers in marine animals to evaluate the health effects of environmental contamination in marine ecosystems. More precisely, the book presents the results obtained during the development and application of biological markers as indicators of exposure/effect to toxic chemicals in marine environments, using diverse sentinel species such as fish, bivalves and crustaceans. An important aspect is also the publication of technical annexes that describe in detail the experimental procedures developed for both chemical and biochemical measurement.