Analysis and prediction of the spatial distribution of EPT (Ephemeroptera, Plecoptera, and Trichoptera) assemblages in the Han River watershed in Korea

Understanding the relationships between environmental factors and aquatic communities at the large scale is important for conserving freshwater biodiversity and sustaining ecological integrity. In this study, we evaluated the ecological status of the Han River watershed in Korea with the predictive distribution maps for EPT (Ephemeroptera, Plecoptera, and Trichoptera) taxa. From large-scale surveys, environmental and biological data for 360 sites in 189 streams and rivers in the Han River watershed in 2012 and 2013 were analyzed. Based on correlation analysis and stepwise multiple regression analysis, the factors influencing EPT richness were altitude, percent of coarse substrate, biochemical oxygen demand (BOD), and total phosphorus (TP). DPI (distribution prediction index), indicating the distribution probability of EPT assemblages, was calculated by using a frequency ratio model. This index was high in the mountainous area where altitude and percent of coarse substrate were high, but low in the urbanized area where BOD and TP were high. Verification of the model indicated high reliability of DPIs as demonstrated by the low root-mean-square-error (RMSE) values between the predicted and observed values. This study provides a basis for the sustainable management of stream ecosystems as well as paves the way for future studies such as those on environmental assessment techniques using aquatic insect communities.