A Study On Exploring Feasibility Of Freshwater Bivalves As Ecological Tools Of Restoring Aquatic Environment

Oxygen consumption rates and filtration rates of Corbicula fluminea,Uniodou glasiae,Arconaia lanceolata,Anodonta woodianawoodiana,Lamprotula bazine and Hyriopsis cumingii were studied in this thesis.Results showed that oxgen consumption rates of Corbicula fluminea,Uniodou glasiae,Arconaia lanceolata,Anodonta woodianawoodiana,Lamprotula bazine and Hyriopsis cumingii by using an eotic obturator were 3.57 mg/kg·h, 3.62 mg/kg·h,2.92 mg/kg·h,2.70 mg/kg·h,1.79 mg/kg·h and 2.39 mg/kg·h respectively when the water temperature was 18±0.5℃,the original concentration of oxygen was 7.8±1.1mg/L, and filtration rates of Corbicula fluminea,Anodonta woodiana,Hyriopsiscumingii,Uniodouglasiae,Lamprotu la bazini, Arconaia lanceolata by mean of stagnant water were 6.42±1.53L/kg·min, 2.10±0.72L/kg·min,1.67±0.43L/kg·min,1.12±0.51L/kg·min,0.74±0.25L/kg·min and 0.93±0.42L/kg·min respectively when the water temperature was 18±0.5℃and original concentration of algae was 1.45×10⁴ind/L.We concluded oxygen consumption rates of bivalves had positive linear correlation with original concentration of oxygen,as the original concentration of oxygen decreased,oxygen consumption rates of six kinds of freshwater bivalves decreased to some extent.Effects of Cristaria plicata Leach,Hyriopsis cumingii and Corbicula fluminea on eliminating algaes in 24 hours were studied in laboratory.Results showed that elimination rates of Cristaria plicata, Hyriopsis cumingii and Corbicula fluminea at the 24th hour were 74.3±2.9%,75.6±2.1%,88.4±3.1% respectively, the effects of three kinds of bivalves on eliminating algaes were significant.T-test indicated that the elimination rate, elimination quantity of algaes in 24h by Corbicula fluminea were significantly higher than that by Cristaria plicata and Hyriopsis cumingii(P<0.05).0-4h Ki of Corbicula fluminea significantly outweighed that of Cristaria plicata and Hyriopsis cumingii(P<0.05).Elimination quantity of algaes by Hyriopsis cumingii increased as the density of Hyriopsis cumingii increased, Hyriopsis cumingii groups at 80g/L had the best effect of eliminating algaes,density of bivalves had insignificant effect of Hyriopsis cumingii on eliminating algaes.Effects of Cristaria plicata and Corbicula fluminea on eliminating algaes were restricted by densities of bivalves, elimination quantity of algaes by Cristaria plicata groups at 80g/L increased slowly after 12h, the density of the best effect of eliminating algaes by Cristaria plicata was 40g/L,elimination quantity of algaes of Corbicula fluminea groups at 20g/L was the biggest after 12h compared with other Corbicula fluminea groups.Effects of Cristaria plicata, Hyriopsis cumingii and Corbicula fluminea on restoring aquatic environment were studied.Results showed that the effects of Cristaria plicata, Hyriopsis cumingii on restoring aquatic environment were relevant with the densities of bivalves.For the Cristaria plicata and Hyriopsis cumingi groups at high density(1866.6g/m²) couldn't reduce concentrations of algaes and nutrients in water,nevertheless increased concentrations of algaes and nutrients,biodisturbance of Cristaria plicata and Hyriopsis cumingi increased the quantity of resuspended sediments and intensified the release of internal nutrients and increased nitrogen and phosphorus contents of sediments. Cristaria plicata and Hyriopsis cumingi groups at low density(466.6g/m²) had better effects on restoring aquatic environment,which significantly reduced concentrations of algaes and nutrients,effects on resuspending sediments and releasing internal nutrients weren't significant, concentrations of Chl a and TN,TP,NH₃ were significantly lower than the control groups(P<0.05).Effects of Corbicula fluminea groups at three kinds of densities on restoring aquatic environment were significant,concentrations of Chl-a and nutrients of water body of Corbicula fluminea groups with three kinds of densties were significantly lower than the control groups(P<0.05),the deposition rates and TN,TP contents of sediment were significantly lower than the control groups(P<0.05),among these, Corbicula fluminea groups at high density(1866.6g/m²)had the best effects of eliminating algaes,nutrients of water body and nutrients contents of sediments.Experimental studies in this thesis showed that Corbicula fluminea had a stronger ability of filtrating algae comparing with other kinds of freshwater bivalves,effects of Corbicula fluminea on eliminating algaes and nutrients were best compared with Cristaria plicata and Hyriopsis cumingii,the degree of biodisturbance by Corbicula fluminea were weaker than Cristaria plicata and Hyriopsis cumingii, the effects of releasing nutrients of substrates were subtle, we concluded that Corbicula fluminea was the suitable species of restoring the ecological environment of aquatic ecosystem.