A distinction between contamination and pollution is useful when we wish to consider what strategies to adopt in researching the impact of anthropogenic activities on the marine environment. Contamination strictly refers to the chemical burden imposed on the system and is evaluated in terms of the concentrations of chemical compounds in various abiotic (e. g water, suspended particulate matter, sediments) and biotic (plant and animal, pelagic and benthic) components. The concept of pollution, on the other hand, infers an assessment of biological response to the measured levels of contamination. This response may be measured at various levels of biological organisation, from molecular events within the cell to changes in such ecosystem properties as nutrient flux and biological productivity. Such measures of biological response need not infer any value judgements regarding putative damage or disturbance to the natural systems, although the biologist will usually have in mind a reference point of normality with which to compare the measured response; departure from this "normality" may then provide a quantitiative index of disturbance. The challenge to scientists engaged in research into marine contamination and pollution is to weld the chemical and biological elements together (always with reference also to the physical features of the environment) so as to provide a coherent framework for the quantitative evaluation of environmental response.