This PhD thesis focuses on the investigation of iron oxide nanoparticles (IONP). Due to the increasing application of iron nanomaterials (NM) in environmental remediation of contaminated sites, tons of these NM will consequently be released to the environment with unknown risks to biota. For assessing effects of IONP, Daphnia magna was used since there are several standardized test protocols available. Due to its sensitivity against most pollutants and its filter-feeding way of life Daphnia is a preferred organism for testing NM in aquatic ecotoxicology. The presented studies show the influence of coating materials and colloidal properties on the effects of IONP on Daphnia in acute and chronic tests. In a further study, the use of IONP for remediation applications and the risk/benefit for the environment from this technique was studied in combinatory exposure acute tests. Furthermore, the Daphnia acute test was critically revised and possible miniaturizations and prolongations are shown
