The aim of the EU water framwork directive (EU WFD) is to achieve a good chemical and ecological status for European water bodies (till 2015). However, to choose the appropriate actions to improve the ecological status, the cause for the poor status has to be identified. For this purpose, tools, such as weight-of-evidence (WoE) approaches, are required that are able to detect chemical induced effects in a multi-stress situation, which is common in anthropogenically modified water bodies. Indices that consider chemical induced changes in in situ communities are important components of WoE approaches (Fig. 1).
In fine, cohasive sediments (often hotspots of chemical pollution) common macroinvertebrate based indices (e.g. SPEAR[%]-Index; Saprobic Index) can rarely be used, as only few macrobenthic species occur in these habitats. Here, meiobenthic invertebrates, such as nematodes, should be used for bioindication. For this purpose, the NemaSPEAR[%]-Index was developed, that uses the percentage of nematode species at risk (NemaSPEAR), that had shown to occur mainly in lowly contaminated (Fig. 2), and rarely in contaminated freshwater sediments. The NemaSPEAR[%]-index has shown to be a suitable measure to assess chemical induced changes in benthic invertebrate communities (Höss et al. 2011; Wolfram et al. 2012).