This volume attempts to summarize the joint efforts of a group of workers who developed systems for analysing marine pollution for use with marine animals and then use these systems to monitor certain select marine populations. Approach taken is to seek pollutant-induced changes in metabolite (e.g. glutathione, ascorbate) concentrations, in hormone concentrations, in enzymes associated with pollutant metabolism (e.g. the cytochrome P-450 mixed-function oxidase system), in immunological capacity and in cellular morphology. The work reported here details the specific methods used and summarizes the results of measurement of the parameters in both pristine and exposed animals. Not all systems exhibited changes in response to the pollutants tested; these systems are also discussed here to help others avoid these potential, but insensitive, markers.