Spring micro-distribution of macroinvertebrate in relation to hydro-environmental factors in the Lijiang River, China

The study investigated the reference state of the macroinvertebrates and their relation to hydro-environmental factors for the Lijiang River, which can be served to assess the impact of flow regulations on the river ecosystem. Samples of water, sediment and benthos were taken from three reaches located in the upstream, middle stream and downstream respectively during March-April 2010. Parameters characterizing flow, chemical and biological conditions were analyzed for each sample. In total, 31 species of 6 classes were identified, including Insecta (13 species), Gastropoda (8 species), Lamellibranchiata (3 species), Crustacea (3 species), Oligochaeta (2 species) and Hirudinea (2 species). The density ranged from 20 ind./m(2) to 3780 ind./m(2) with an average of 750 ind./m(2). The macrofauna composition was Gastropoda (48.0%), Insecta (23.9%), Lamellibranchia (14.9%) and the others (13.2%). The biomass ranged from 0.9 g/m(2) to 1001.6 g/m(2) with an average of 150.8 g/m(2). The macrofauna composition was Gastropoda (70.5%), Lamellibranchia (24.7%) and the others (4.8%). Canonical correspondence analysis (CCA) revealed that species distributions were mainly governed by flow velocity, conductivity, chemical oxygen demand (COD) and total nitrogen. (C) 2012 International Association for Hydro-environment Engineering and Research, Asia Pacific Division. Published by Elsevier B.V. All rights reserved.