Assessment of environmental quality within MSFD involves chemical and biological indicators of the contaminant pressure. Embryo aberrations in amphipods (ReproIND) is a supplementary indicator for biological effects of contaminants in Baltic sediments, and much efforts are currently undertaken within HELC OM to validate this indicator. ReproIND reflects exposure to complex mixtures of individual substances with different solubility and physicochemical properties. The chemical activity integrates these properties with contaminant quantities and provides a robust approach for addressing mixture toxicity. We propose to apply the chemical activity concept to improve our understanding of the mixture effects and to develop a new approach for indicator validation. We will use chemical activity to convert site-specific contaminant levels into one currency to (i) provide a basis for comparisons of ReproIND data from different sites, (ii) test predictability of ReproIND as well as its specific components to the contaminant pressure; and (iii) facilitate indicator validation for management actions. Existing
long-term data and archival collections of amphipods and sediments as well as experiments will be used to study contaminant behavior and the mechanisms of the joint sublethal effects. The output will be used to develop a framework for validation of biological effect indicators across different basins and to promote ReproIND to the core indicator within MSFD.
