Changes in the Benthic Macroinvertebrates in Xiangxi Bay Following Dam Closure to Form the Three Gorges Reservoir

Benthic macroinvertebrates were assessed monthly in Xiangxi Bay of the Three Gorges Reservoir for two years after the initial closure of the dam. Mean total density of macroinvertebrates varied from 275 ind./m2 during the first year to 5,094 ind./m2 during the second year, and the community of 50 taxa was overwhelmingly dominated by oligochaetes and chironomids (44 and 48% of the total taxa, respectively). As sediment accumulated in the substrate of the bay, the species composition changed dramatically, with oligochaetes comprising 91.3–99.3% of the total abundance during the second year. The dominant oligochaetes were Limnodrilus hoffmeisteri and Nais inflate. The chironomids Procladius sp., and Polypedilum scalaenum group sp. were similarly abundant in both years.