The Effect Of Bellamya Purificata On The Repair Of Nitrogen And Phosphorus In The Sediment Of Pond

Aquaculture pond ecosystems are typical artificial farming system with simple and fragile ecological structure,which is difficult to achieve self-restoration from the pollution state.Excessive accumulation of nitrogen and phosphorus is the main cause of water pollution in aquaculture pond.Previous studies have indicated that the nitrogen and phosphorus accumulated in sediments could result in serious pollution in the overlying water.Hence,the restoration of sediments is very important in avioding the water pollution.Therefore,the effect of the bioturbation derived from Bellamya purificata on the sedimentary nitrogen and phosphorus in aquaculture pond was studied in this research in order to provide feasible new ideas or methods to reduce the nitrogen and phosphorus accumulation in the sediments.In this experiment,Bellamya purificata was used as the research object to study the effect of the bioturbation on the nitrogen and phosphorus in pond sediment.This experiment included indoor simulation experiment and field experiment,treatment groups and control groups were set up in each experiment.The redox potential,nitrogen and phosphorus forms,and extracellular hydrolase activities in the sediments of each specific group were determined.The major results were as follows:(1)the bioturbation of Bellamya purificata could significantly reduce the contents of the total nitrogen,total phosphorus,organic nitrogen,and organic phosphorus in the sediment of the treatment group relative to the control group(P<0.05),and significantly increased the contents of inorganic nitrogen and inorganic phosphorus in the sediment of the treatment group compared with the control group(P<0.05).(2)The bioturbation of Bellamya purificata significantly increased the redox potential in the sediment of the treatment group relative to the control group(P<0.05);(3)The bioturbation of Bellamya purificata significantly increased the nitrate reductase activity and reduced the urease activity and alkaline phosphatase activity(P<0.05)in the sediment of the treatment group compared with the control group(P<0.05),while no significant differences were observed in peroxidase activity between the treatment group and control group(P>0.05).The results showed that:(1)Bellamya purificata can effectively inhibit the excessive accumulation of organic nitrogen and organic phosphorus in the sediment through bioturbation such as feeding,crawling,and excavation;(2)Bellamya purificata has a significant promoting,effect on nitrate reductase activity.It has significant inhibitory effect on urease and alkaline phosphatase activity,and has no significant effect on peroxidase activity.(3)The decrease in organic nitrogen and phosphorus might be due to the bioturbation,which can significantly increase the redox potential of the sediment and promote the degradation and transformation of organic nitrogen and phosphorus.Therefore,we can try to use the bioturbation of Bellamya purificata to control the content of organic matter in the pond to a certain extent through reasonable stocking and harvesting,in order to achieve the purpose of prevent the accumulation of nitrogen and phosphorus in the sediment.