Chiang Mai Journal of Science

     Aquatic insects ar e among the most frequently used macroinvertebrates in freshwater monitoring and assessment worldwide. However, little attention has been paid to the inclusion of aquatic insects in the biological assessment of water quality and health, especially in Vietnam. In the current study, we altitudinally investigated the diversity of aquatic insects as well as their relationships with physico-chemical parameters in Thac Bac stream, Tam Dao national park, in which high-altitude sites highly experience human disturbance while low-altitude sites are conservative areas. A total of 122 species belonging to 111 genera, 56 families and 9 orders of aquatic insects were identified in the current study. Further, we found altitudinal changes, both in the biodiversity of aquatic insects and water quality parameters. The biodiversity of aquatic insects was higher in the low-altitude sites ranging from H’=3.31 in site St5 to H’=4.09 in site St6 compared to that of high-altitude stream sites ranging from H’=1.43 in site St1 to H’=2.29 in site St3. Moreover, a strong correlation between the aquatic insect biodiversity and several water quality parameters was found, in which dissolved oxygen and air temperature were positively correlated with the biodiversity index while altitude and electrical conductivity were negatively correlated with the biodiversity index. The results of this study provide a useful basis for appropriate water management using aquatic insects as bioindicators to assess human impacts on stream systems in Vietnam.