The predator-prey interaction in freshwater ecosystems is a crucial area in the ecological study field and one of example to find such interaction is to investigate stomach contents. However, traditional method through visual inspection often induce misidentification, as it depends critically on intactness of physically visible data. In this study, we utilized Next-Generations Sequencing (NGS) technology to test the applicability stomach content analysis and overcome such limitation. NGS was applied to analyze the stomach contents of the Hemibarbus labeo, Tachysurus fulvidraco, and Plecoglossus altivelis collected in the lower part of Nakdong River. As a result, T. fulvidraco had a higher number of Animalia operational taxonomic units (OTUs) intake rate than H. labeo. At the same time, P. altivelis had higher number of Plantae OTUs intake rate than T. fulvidraco and higher Protozoa OTUs intake rate than H. labeo respectively. Therefore, NGS technology application enable to overcome traditional method’s limitation and discover hidden interspecific interaction which can further be used in appropriate habitat assessment.

E171, a mixture of titanium dioxide, has been widely used as a food additive due to its whitening effect and low toxicity. However, it has been proven that E171 is no longer safe for public health. So far, there are insufficient studies on the toxic effects of E171 on organisms especially using standardized test methods. In this study, toxicity assessments of E171 to two aquatic species, water flea (Daphnia magna) and zebrafish (Danio rerio), were performed using modified standardized test methods based on the physicochemical properties of E171. The hydrodynamic diameter, polydispersity index, and turbiscan stability index (TSI) were measured to ensure the dispersion stability of E171 in exposure media during the test period. The EC50 for immobilization of water flea was 141.7 mg L-1 while zebrafish was not affected until 100 mg L-1 of E171. Measurements of reactive oxygen species (ROS) and antioxidant enzyme activities confirmed that E171 induced oxidative stress, leading to the activation of superoxide dismutase and catalase in both water flea and zebrafish, although the expression of antioxidant enzyme genes differed between species. These results suggested the potential risk of E171 to aquatic organisms and provided toxicological insights into the impacts of E171 on the environment.