The community structure of zoobenthos was investigated in Xiangxi Bay,Three Gorges Reservoir, from August 2003 to August 2004. Benthic invertebrate samples were sampled monthly except December 2003 with a modified Peterson grab ( grab surface area 0.0625 m(2)) The samples were passed through a sieve of mesh size 200 mu m and material retained was preserved in 10% formaldehyde for sorting of the invertebrates from the sediment. All soiled invertebrates were identified as far as possible. Benthic abundance and biomass were calculated per unit area of sediment. A total of 26 taxa were identified, among which, 2 Lamellibranchia (belonging to two families, 7.7% of the total taxa number), 13 Oligochaeta (two families, 50%,) 10 Chironomidae 2 (38.5%) and 1 other animal (3.8%). The average density and biomass were 276 ind./m(2) and 0.301 g/m(2), respectively. Oligochaetes and chironomids constituted the major groups, and Limnodrilus hoffmeisteri, Procladius sp., Branchiura sowerbyi, Tubificidae spl. and Polypedilum scalaenum, group sp. were the common taxa in this reservoir system. Among them, L. hoffmeisteri and Procladius sp. were the dominant species, and contributed to 37.0% and 28.3% of the total density, respectively. While compared with Procladius sp., L. hoffmeisteri were influenced by impoundment more evidently. The standing crop of zoobenthos in Xiangxi Bay was relative low, compared with other similar reservoirs. While the taxa was similar. Our studies demonstrated that the standing crop was increased gradually along with the time. The total density and biomass were increased 7.8 and 13.3 times as those of initial impoundment, separately. Polluted-tolerance taxa overwhelmed the system indicating that the water quality was degrading. Because oligochaetes may function as an indicator of high sediment loading and the relative abundance of oligochaetes and chironomids in Xiangxi Bay varied obviously among months, the sediment loading in Xiangxi Bay might be not serious.
Shao Mei-Ling; Xie Zhi-Cai; Ye Lin; Cai Qing-Hua (email@example.com).Monthly change of community structure of zoobenthos in Xiangxi Bay after impoundment of Three Gorges Reservoir,Acta Hydrobiologica Sinica,2006,30(1):64-69