John Wiley & Sons, Ltd.

Response of bacteria and meiofauna to iron oxide colloids in sediments of freshwater microcosms

The use of colloidal iron oxide (FeOx) in the bioremediation of groundwater contamination implies its increasing release into the environment and requires an assessment of its ecotoxicological risk. Therefore, microcosm experiments were carried out to investigate the impact of ferrihydrite colloids (Fh‐Col) on the bacterial and meiofaunal communities of pristine freshwater sediments. The effects of Fh‐Col were compared with those of Fh macro‐aggregates to discriminate between colloid‐specific and general FeOx impacts. The influence of Fh‐Col on the toxicity of sediment‐bound fluoranthene was also considered. At high concentrations (496 mg Fe kg‐1 sediment dry weight, dw), Fh‐Col had a significant, but transient impact on bacterial and meiofaunal communities. While bacterial community composition specifically responded to Fh‐Col, a more general FeOx effect was observed for meiofauna. Bacterial activity responded most sensitively (already at 55 mg Fe kg‐1 dw) without the potential of recovery. Fh‐Col did not influence the toxicity of sediment‐bound fluoranthene. Significant correlations between bacterial activity and meiofaunal abundances were indicative of trophic interactions between bacteria and meiofauna and therefore of the contribution of indirect food‐web effects to the observed impacts. The results suggest that the application of Fh‐Col for remediation purposes in the field poses no risk for benthic communities, given that, with the exception of generic bacterial activity, any negative effects on communities were reversible. This article is protected by copyright. All rights reserved

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