Macroinvertebrate community succession in the Three-Gorges Reservoir ten years after impoundment

The Three-Gorges Reservoir (TGR) is one of the world's largest reservoirs, whose ecological effects have attracted much attention. Focusing on the macroinvertebrate community dynamics and its relationship with hydrological factors ten years after impoundment, we provide an overview of the macroinvertebrate community succession in the TGR including determining factors. Pioneer species in the TGR was Polypedilum scalaenum while Nais inflata became dominant during non-flooding seasons commencing the second impounding year with extremely high relative abundance (up to 97%). An increase of water-level fluctuation range in the third impoundment stage did not significantly alter the steady seasonal pattern of macroinvertebrate community which formed following the second impounding year. MRPP (Multi-response Permutation Procedure) analysis showed significant differences between-season (A<0.3, P < 0.01) except between summer and autumn (A = −0.0165, P = 0.773). Macroinvertebrate assemblages were evidently correlated with inflow discharge during flood seasons and water retention time during non-flood seasons. Macroinvertebrate density showed severe reduction in summer following high velocity inflow current, and disappeared in autumn following vast sedimentation. The macroinvertebrate community gradually became reestablished following reduction of inflow discharge and sedimentation and increase of water retention time in winter and spring. Our analyses suggest that macroinvertebrate community in the TGR is regulated by the subtropical monsoon climate, commencing with seasonal cycles of destruction followed by reestablishment.