This thesis deals with the effects of ZnCl2 and ZnO nanoparticles (ZnO NPs) on Pseudokirchneriella subcapitata (as a single species toxicity test) and aquatic microbial communities (as a community-level toxicity test). The effects of metal ions like Zn2+ on different organisms can be highly variable and there are some studies about the side effects of this metal ion on species occurring in aquatic microbial communities like bacteria, algae and diatoms; however, the effects of metal ions on single species is probably not enough accurate to base risk assessment decisions on. In order to obtain...