Community characteristics of aquatic insects and bioassessment for water quality in lower order streams in Liangshui and Maoershan watersheds,Heilongjiang,China
Abstract:Aquatic insects in lower order streams under landscapes with different vegetations in Liangshui National Natural Rserve and Maoershan Experimental Forest Farm were collected and identified to analyze the community composition, seasonal dominant concentration and foundational feeding group, in May、August and October,2006. The stream water quality was assessed by biological indicator using Shannon-Weiner diversity index, community similarity index and biotic index. Totally 4907 aquatic insect individuals were collected and identified to 38 families, 8 orders. Trichoptera, Ephemeroptera, Plecoptera and Diptera were dominant groups, accounting for 91.13% of all the aquatic insects collected. Most aquatic insects were found in old growth forest streams in Liangshui, accounting for 58.98% of the total, much more than that found in second growth forest streams in Maoershan, and the least were found in farmland streams in Maoershan. The aquatic species diversity in second growth streams was greater than that in the old growth and farmland streams, and the percentages of foundational feeding group in second growth streams were more balanced. The species in Odontoceridae, Neoephemeridae and Capniidae were selected as biological indicators for high stream water quality. There was relationship between seasonal dominant concentration of aquatic insects and the assessment results for water quality with Shannon-Weiner diversity index, the species diversity reduced gradually with the increasing of water pollution level. Community similarity index indicated that the composition of aquatic insect community was not influenced by water quality in old growth and second growth streams , but moderate influence was found in farmland streams. The results of biotic index analysis suggested that water quality of all streams surveyed was good at anytime except for farmland stream which was slightly polluted in October.