Introduction

In the marine environment a widely used definition of pollution is the ‘introduction by man, directly or indirectly, of substances or energy into the marine environment (including estuaries) resulting in deleterious effects such as harm to living resources, hazards to human health, hindrance of marine activities, including fishing, impairing quality for use of sea-water and reduction of amenities’ (GESAMP 1982 – my emphasis). The increasing sophistication of analytical chemical methods means that we can detect contamination by a wide range of chemicals in almost any aquatic environment (see Chapter 5). But the rational regulation of direct contaminant discharges to the environment and the setting of priorities for dealing with contaminants arising from diffuse sources requires us to be able to identify the subset of cases of contamination where deleterious effects are, or may be, occurring. There has been considerable recent improvement in methods for prospective risk assessment – methods that allow an assessment of whether particular concentrations of a substance might cause ecological effects in the field. For example, the development of species sensitivity distributions has given greatly improved information on whether the sensitivity of standard laboratory test organisms reflects the sensitivity of the much wider range of organisms that occur in the field (see, e.g., Maltby et al. 2005), and there is discussion of risk assessment methods elsewhere in this volume (Chapters 5 and 9). However, determining whether an individual substance actually is having deleterious effects on the ecology at any particular location remains a major challenge for ecotoxicology.