Before dredging, there were six species of Mollusca?three species of Oligochaeta and one of Hirudinea in Huangdu, and one Mollusca and four Oligochaetas in Huacao.

• 疏浚后两个断面的生物量和密度均低于疏浚前,但在疏浚后的一年内,密度呈持续上升趋势;