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The natural flow regime is confirmed to be the main driving factor in maintaining diverse species and abundant production of river floodplains. However, disturbance of human activities have affected natural hydro-geomorphical process, reduced habitat heterogeneity, and weakened ecological service functions. Thus, it is necessary to assess ecological water requirements and furthermore provide a quantitative operational basis for restoring natural flow regime. Macroinvertebrates are considered as good indicators of hydrological regime changes due to their confinement to the bottom, limited abilities of movement, and low tolerance. This paper deals with systematic ecological investigations in the Wuhan branch of the Yangtze River during 2007–2008. Altogether, 32 taxa of macroinvertebrates belonging to 13 families and 27 genera were identified. The density and biomass of total macroinvertebrates were 181 ind m −2 and 0.29 g dry mass m −2 , respectively. Canonical Correspondence Analysis (CCA) revealed that the important environmental factors influencing macroinvertebrate abundance were flow velocity (U), water depth (Z), and total nitrogen (TN). The relation between habitat weighted usable area and water discharge was analyzed on basis of creating suitability curves. Weighted usable area of habitat showed unimodal changes with increasing water discharge, i.e., first increased and then decreased, and weighted usable area of habitat reached the maximum when flow discharge was 21,000 m 3 s −1 . [ABSTRACT FROM AUTHOR]

The Chinese mitten crab ( Eriocheir sinensis (H. Milne Edwards, 1854)), is a highly invasive species and poses a great threat to endemic species and infrastructure in Europe and North America. Although it is partly herbivorous and prefers to live in lakes with abundant submersed macrophytes, little is known about its effect on macrophytes. We used its native range, the mid-lower Yangtze Basin where the species has been cultured intensively for decades, as our study site to test the hypotheses that (1) high crab densities weaken the positive feedback between macrophytes and water transparency, and that (2) the effects of crabs become apparent only on decadal timescales and (3) are density dependent. We used correlative analyses based on 12 years of monitoring and multi-lake comparisons among 20 sub-areas in 4 lakes. High crab densities were found to cause negative effects on submersed macrophytes and transparency, and to weaken the positive relation between macrophytes and transparency. High densities of macrophytes showed resilience to disturbance from crabs. This resilience, however, reduced with continuous presence of high crab densities. Crab densities were strongly positively related with total phosphorus and negatively with transparency and total nitrogen. Phosphorus concentrations and transparency were not related with phytoplankton chlorophyll a , suggesting that crab’s bioturbation strongly influences water quality. The apparent resilience of the dense macrophyte stands should however, not delay attempts to eradicate the crab where it is invasive as this becomes more difficult once they have become established. When macrophyte abundance is already low at the time of invasion, immediate loss of macrophytes may occur. [ABSTRACT FROM AUTHOR]