Construction And Function Of The Integrated Ecosystem Of Reservoir,Aquaculture Pond And Paddy Field(IERAP)

Based on the principle of ecological engineering,this study constructed a water source fish pond paddy field composite ecosystem.By studying the dynamic changes in water quality in aquaculture ponds,the water purification efficiency of the rice field ditch system and each unit,and the production performance of the composite ecosystem pond and rice field,the functions of each unit in the water source fish pond rice field composite ecosystem are analyzed.The nitrogen and phosphorus utilization efficiency of the system is evaluated through nitrogen and phosphorus budget.The main research findings are as follows:（1）Based on the principles of ecological engineering,a water source fish pond paddy field composite ecosystem was constructed.The aquaculture tail water is lifted by a water pump and enters the paddy field.After being purified by the surface flow of the paddy field,it flows into the agricultural ditch,and then returns to the water source through the strengthened ditch.The water source collects the purified aquaculture tail water and provides aquaculture water for fish farming.（2）During the aquaculture period,the composite ecosystem can effectively maintain stable levels of dissolved oxygen（DO）,p H,ammonia nitrogen（TAN）,and nitrite nitrogen（NO₂^--N）in ponds.The composite ecosystem has a significant regulatory effect on indicators such as total nitrogen（TN）,nitrate nitrogen（NO₃^--N）,permanganate index(COD_Mn),and chlorophyll a（Chl a）in the circulating pond..After the operation of the composite ecosystem,the relative density of blue-green algae decreased by 30.38%,the relative density of green algae increased by 28.86%,and diatoms also showed a slight increase.The Margalef richness index in the circulating pond was significantly higher than that in the control pond.A composite ecosystem can increase the diversity of phytoplankton in ponds,increase community complexity,and maintain a relatively stable pond environment.（3）By exploring the purification effect of rice fields under different hydraulic loads,the optimal hydraulic load was determined to be 0.03 m³/（m²·d）.Under this hydraulic load,the rice field ditch collaborative purification system can effectively intercept pollutants in the aquaculture tail water.The average values of TN,TAN,NO₃^--N,TP,COD_Mn,and TSS in the system’s effluent are 1.33,0.28,0.11,0.19,6.61,and 12.00 mg/L,respectively,with an average removal rate of 86.73%,65.95%,72.94%,89.26,85.77%,and 93.68%.The variation of TN,TP,and COD_Mn along the process in the rice field ditch collaborative purification system follows a linear reduction model.The comprehensive water quality of the pond aquaculture tail water has been significantly improved after being treated by the rice field ditch collaborative purification system.The relevant water quality meets the first level discharge requirements of the"Freshwater Pond Aquaculture Water Discharge Requirements"（SC/T 9010-2007）,and the water quality indicators of the water source meet the "Fishery Water Quality Standards"（GB 11607-1989）.The rice field ditch water source system can be used for the standard discharge or reuse of pond aquaculture tail water.（4）The feed coefficient of the control pond was 1.88±0.11,and the feed coefficient of the circulating pond was 1.45±0.11.The composite ecosystem significantly reduced the feed coefficient of the aquaculture pond.The rice yield under high-intensity irrigation and drainage treatment in the paddy field was 10477 kg/hm2,and the nitrogen and phosphorus content of the paddy soil was increased after tail water irrigation and drainage.The study on nitrogen and phosphorus balance shows that the composite ecosystem improves the efficiency of nitrogen and phosphorus utilization,and the relative utilization efficiency of nitrogen and phosphorus in the circulating pond is higher than that in the control pond,respectively...