A short overview of molecular biomarker strategies with particular regard to recent developments in earthworms

Biomarkers are increasingly used, especially in aquatic toxicology, as sub- lethal. stress indicators for hazard assessment. The objective of the prese nt overview was to seek some patterns in this rapidly expanding field so as to facilitate progress toward a flexible framework within which earthworm biomarkers can be deployed to maximal terrestrial ecotoxicological advantag e. Three trends were evident. Trend I - the application of biomarkers seque ntially as a hierarchial series : Tier I biomarkers responding indiscrimina tely to general stress; Tier IT biomarkers responding to a family of(chemic ally) related stressors; Tier III biomarkers responding discriminately to s pecific stressors. Trend 2 - the linkage between levels, whereby limited ef forts have been made to establish relationships that are (ideally) mechanis tic rather than merely statistically correlative between low-organisational -level (i.e. molecular and cellular) responses and higher level (i.e. life- cycle parameters, population, community) alterations. Trend 3 - the derivat ion of 'value added' information from biomarker arrays or suites analysed b y multivariate techniques to yield more information than from biomarkers de ployed and interpreted individually. Trend I is useful for rapid screening of new agrochemicals, early warning of perturbations in habitats contaminat ed, with single and multiple stressors, and to quickly assess recovery afte r ameliorative or remediative interventions. Trend 2 is potentially useful for predicting the long-term L ecological consequences of toxicant release based on short-tr;nn biological effects. Trend 3 will increasingly be usefu l in comprehensive, perhaps macro-scale, environmental diagnostics.