Biomarker applications in ecotoxicology: bridging the gap between toxicology and ecology

Biomarkers have been used increasingly to investigate the adverse impacts of pollutants on different aspects of the structure and function of the ecosystem. In this manuscript, a conceptual overview and general evaluation of the present biomarker research in the rapidly expanding area of ecotoxicological research is presented. In general, ecotoxicological studies can be divided into 2 basic approaches, largely due to the historical backgrounds and the intrinsic differences in the merging sub-disciplines, namely the "toxicological" versus the "ecological" oriented approach. At present, this discrepancy largely hampers the application of biomarker techniques in environmental risk assessments. In order to use these effect- and/or exposure-based biomarker criteria in an applied ecological context, quantitative relationships between the sub-organismal effects and effects occurring at higher levels of biological organization need to be developed. The potential of certain energy-based biomarker criteria to bridge the existing gap between both types of research is illustrated for the waterflea Daphnia magna. It is demonstrated how short term tin vitro) digestive enzyme-based effects as well as Cellular Energy Allocation measurements allow estimation of threshold concentrations which are indicative of adverse effects at the (supra) organismal level.