Abstract: Three micro-scale controlled experiments were established to examine the ecological function of Bellamya sp. and their affecting mechanisms upon water. Due to the N and P release through the Bellamya sp. metabolism under controlled conditions, the concentrations of different N and P forms in water were obviously increased. After 430 hours incubation, the concentrations of dissolved total nitrogen (DTN) and dissolved total phosphorus (DTP) in water were increased by 0.73-2.56 times and 1.85-3.41 times, respectively. Under the high nutrient concentrations, the N and P release by Bellamya sp. was inhibited. Meanwhile, Bellamya sp. showed a positive effect on the shortterm deposition of suspended particulate matter (POM), which was related to the constituents and concentrations of POM. The sedimentation rates in both kaolin and eutrophic water with high initial turbidity showed significant positive relationship with snail density. Furthermore, Bellamya sp. greatly reduced the chlorophylla concentration in water in a short period, and the removal rate was positively correlated with snail density. However, the chlorophylla concentration was increased rapidly with increasing incubation time. The feeding activities of Bellamya sp. and the consequent nutrient release stimulated the chlorophyta instead of cyanobacteria as the dominant species.

Key words: heavy metal, chemical speciation, risk assessment code method., agricultural soil, potential ecological risk index