Study On The Removal Of Different Algae By Bellamya Aeruginosa

Global warming and eutrophication facilitate the occurrence and development of harmful algae blooms.Cyanobacterial blooms and its severe effects on the aquatic ecosystems have been becoming the focus in the field of water environment.Generally,there are three ways to control algae blooms:physical method,chemical method and biological method.Currently,biological controls are getting more and more attentions due to the economically and environment-friendly characteristics.In this study,Bellamya aeruginosa,which has a wide distribution and the highest yield in the freshwater of China,was chosen as the biological control organism.A series of laboratory tests were conducted to study the removal effect of two axenic Microcystis aeruginosa strains(a toxic one called FACHB-905 and a non-toxic one called FACHB-526),coupled with an axenic Chlorella vulgaris strain(FACHB-8)and an axenic Scenedesmus obliquus strain(FACHB-416),by Bellamya aeruginosa.Furthermore,the removal ability of Bellamya aeruginosa with various number or weight under different algae supplements were compared.The effective removal limits of Bellamya aeruginosa on different algae were also analyzed.The main contributions of this study are as follows:(1)In all treatments,Bellamya aeruginosa could remove lots of algae rapidly.The removal rates of the toxic Microcystis aeruginosa,non-toxic Microcystis aeruginosa,Chlorella vulgaris and Scenedesmus obliquus were 73.60%,73.21%,64.18%and 51.13%,respectively.At the end of this study,Chlorella vulgaris was almost completely removed by Bellamya aeruginosa,while the other strains were partially removed.Due to the size of whole body and feeding organ,Bellamya aeruginosa presented a better removal effect on Chlorella vulgaris and Microcystis aeruginosa,than Scenedesmus obliquus.Additionally,the removal rate of non-toxic Microcystis aeruginosa was higher than the toxic one,for the reason that toxic Microcystis aeruginosa produced a large number of microcystins and accumulated in Bellamya aeruginosa at the end of the study.(2)In 600 mL algae cultivations with an initial cell density of 5×106 cells mL’1,the algae could be removed effectively when there were 10 or 15 Bellamya aeruginosa individuals in the cultivation.For 5 Bellamya aeruginosa individuals treatment,the control organisms was not enough for removing all the algae cells,while 20 individuals caused interspecific competition of Bellamya aeruginosa.Additionally,the removal effect of algae cells by Bellamya aeruginosa with a weight of 3 g was better than the ones with weights of 2 g and 1 g.Thus,the heavier Bellamya aeruginosa individuals were more suitable for removing algae blooms in the natural freshwaters.(3)In 600 mL algae cultivations,the removal effect of algae cells by the 10 Bellamya aeruginosa individuals differed with the initial algae cell density.The algae cells could be completely removed when the cell density was less than 1×106 cells mL-1 for Chlorella vulgaris and Microcystis aeruginosa,and less than 2×105 cells mL-1 for Scenedesmus obliquus.For all algae strains,Bellamya aeruginosa could only partially remove the algae cells when cell density was more than 5×106 cells mL-1.This study verified the feasibility of Bellamya aeruginosa used to control algae blooms as a non-traditional bio-manipulation organisms,and revealed the effective limits between Bellamya aeruginosa individuals and algae cell density.