To explore the status of macroinvertebrate communities and the main influencing factors, an investigation was carried out at 29 sampling points (4 sections) and 40 sampling points (5 sections) in the middle reach of the Yangtze River, respectively in April and October in 2014. 34 species were identified in April (spring) and 32 species in October (autumn). Arthropods is the dominant class of macroinvertebrate in both seasons, up to 56% and 35% respectively. Spring’s species abundance, the average density as well as the biomass are the highest in two quarters, and from top to bottom in the middle reach of Yangtze River biomass reduced gradually. The results of functional feeding groups show that collector-gatherers are the main components in the middle reach of Yangtze River in spring (40.25%) and autumn (59.3%). The results of tolerance value show that semi-tolerant to pollution and pollution tolerant organisms are the main components in the middle reach of Yangtze River and Wuhan section has more pollution tolerant organism in the two quarters. The correlation analysis on 5 kinds of functional feeding groups and three kinds of biological standing crop with the 7 environmental factors show that the influence of environmental factors on macroinvertebrate is different in the spring and autumn, TP and TN as well as particle size are the main environmental factors in spring, while in autumn, the benthic animals are mainly affected by pH, dissolved oxygen and transparency. This study has a comprehensive understanding of the benthic fauna from several aspects and can provide basic information for intensive research of the Yangtze River.

Hyriopsis cumingii and corresponding sediment in five respective monitoring sections of Poyang Lake were sampled in autumn 2014, followed by the detection of rare earth elements (REEs) in the soft tissue of Hyriopsis cumingii and sediments treated by BCR sequential exaction. As results, the mean value of total REEs in the soft tissue of Hyriopsis cumingii was 15.52 mg/kg, and light REEs were more easily accumulated, indicating that the biological effect of light REEs on Hyriopsis cumingii was stronger than heavy REEs. Correspondingly, the mean value of total REEs in sediments was 285.22 mg/kg with higher light REEs, suggesting the strong terrigenous properties. The REEs concentration in the sediment treated by BCR sequential extraction ranked as: residual fraction>reducible fraction>oxidizable fraction>exchangeable fraction. The exchangeable fraction displayed the lowest REEs concentration but the largest difference in spatial distribution; however, they were all under low risk level analyzed by Risk Assessment Code. Significant and positive correlations can be observed between REEs in Hyriopsis cumingii and that in the oxidizable fraction of sediments, suggesting that the bioavailability of REEs would mainly depend on REEs bound to organic matter.