Study On Nitrogen And Phosphorus Budget Of Micropterus Salmoides In In-pond Raceway Aquaculture Systems Versus Usual Pond Aquaculture Systems

With the increasing demand for aquatic products,the aquaculture industry has developed rapidly.However,with the continuous development of society and economy and the increasing awareness of environmental protection in recent years,UPA mode have faced many problems such as excessive breeding density,low survival rate,frequent disease,and breeding pollution,which hindered the green and healthy sustainable development of aquaculture.Therefore,it is urgent to optimize the existing pond culture mode,improving the quality of aquaculture water,ensuring the quality and safety of aquatic products,and reducing the discharge of aquaculture wastewater.In-pond Raceway Aquaculture?IPRA?can collecte fish excrement and build purified water pond,improve the efficiency of water recycling and reduce the use of antibiotics and other drugs,it is a revolutionary change to usual pond aquaculture.This study took Micropterus salmoides as the research object,and compared the changes of environmental factors and nitrogen and phosphorus budget between IPRA mode and UPA mode,so as to provide theoretical basis and reference for the reasonable evaluation of the ecological benefits of this new mode.Monitoring the water quality of the two breeding modes throughout the breeding cycle found that the dissolved oxygen content of the IPRA mode was 6.78±0.08mg/L,and the UPA mode was 6.55±0.11 mg/L.There was a significant difference between August and October?P<0.05?.There was no significant difference in water temperature and p H change between the two modes?P>0.05?.In the UPA mode,total nitrogen was significantly different between August and September?P<0.05?,and total phosphorus was significantly different between September and October?P<0.05?.The content of nitrite and COD_Mnin IPRA mode was not significantly different from that in UPA mode?P>0.05?.The ammonia nitrogen content in the IPRA mode during the cultivation period was always lower than that in the UPA mode,and the ammonia nitrogen content in the ponds in the IPRA mode was significantly lower than that in the UPA mode in August and September?P<0.05?.The water consumption per unit area and drainage per unit yield during the IPRA cultivation process were lower than the UPA mode.Compared with UPA mode,IPRA mode has the characteristics of concentrated pollution collection.The sediments such as feces are mainly deposited at 1-6m after the pollution collection area.The area between 1 and 6m after the pollution collection area accounts for 1%of the pond area,but the sediment of 1 and 6m after the pollution collection area accounts for 3.4%of the total pond sediment,accounting for 4.35%of the total nitrogen output and 4.75%of the total phosphorus output.In the IPRA mode,after removing the aquaculture tank area,the sediment produced by per unit fish yield per unit area was 0.064m3/kg/ha lower than that of the UPA mode?0.075m3/kg/ha?.Therefore,the sediment deposition of IPRA model is more concentrated,and it is more convenient to clean up,the sediment produced by per unit fish yield per unit area of IPRA model is less,which has good ecological benefits.In order to reveal the biodiversity of phytoplankton community and bacterial community in IPRA mode and UPA mode,phytoplankton community and microbial community were monitored.The results show that the IPRA mode were identified 64species of phytoplankton?including 17 species undefined?,UPA mode were identified49 species of phytoplankton?including 16 species undefined?.The average density of phytoplankton in IPRA mode?42.65-72.80×106ind/L?was lower than that in UPA mode?71.15-101.12×106ind/L?.The density and biomass of phytoplankton in UPA mode from July to September were significantly higher than those of IPRA mode.Among them,the density and biomass of cyanophyta in UPA mode were significantly higher than those of IPRA mode.In October to November,the Shannon-Wiener diversity index,Margalef index,and Pielou index of the IPRA mode were significantly higher than those of the UPA mode.Therefore,the IPRA model had higher phytoplankton diversity,more stable community structure,and less impact of cyanobacteria on water quality.Canonical Correspondence Analysis?CCA?results show that the main driving factors of phytoplankton in the IPRA mode are water temperature,permanganate index,total nitrogen and total phosphorus,while the main driving factors of phytoplankton in UPA mode are total nitrogen,total phosphorus,ammonia nitrogen,and nitrite nitrogen.The dominant phylum of microbial communities in the two mode was proteobacteria.In IPRA mode,The Chao1 index and ACE index?1524.74 and 1607.31?of microbial community were lower than that of UPA mode?2635.61 and 2723.95?,Shannon diversity index?5.22?was lower than that of UPA mode?6.30?,and Simpson index?0.02?was higher than that of UPA mode?0.01?.The low content of vibrio,aeromonas and other common pathogens in aquaculture in the core microorganisms of the two models indicated that the IPRA model did not increase the risk of bacterial disease outbreak in the case of increasing the density of Micropterus salmoides in the aquaculture tank.The water quality factors affecting the microbial community in IPRA mode were permanganate index,nitrite nitrogen and total ammonia nitrogen,while the water quality factors affecting the microbial community in UPA mode were permanganate index,total organic carbon and nitrite nitrogen.The body length of Micropterus salmoides in UPA mode was significantly faster than that in IPRA mode during 120 to 150 days?P<0.05?.After 150 days of aquaculture,the weight gain rate in UPA mode was significantly higher than that in IPRA mode?P<0.05?.There was no significant difference in the specific growth rate of Micropterus salmoides in the two modes.The survival rate of IPRA mode was significantly higher than that of UPA mode?P<0.05?,and there was no significant difference in feed conversion ratio.The results of the input and output of nitrogen and phosphorus of Micropterus salmoidesin IPRA and UPA mode showed that the feed was the main source of nitrogen and phosphorus in aquaculture,and the nitrogen input of the feed accounted for 94.58%of IPRA mode,which was less than that of UPA mode?94.75%?.Phosphorus input of the feed accounted for 89.19%in IPRA mode,lower than 91.81%in UPA mode.In the two modes,sediment deposition and fish harvesting are the main ways of the output of nitrogen and phosphorus.Sediment deposition accounts for 51.44%and 51.71%of the output of nitrogen and phosphorus in IPRA mode,and 53.98%and 59.57%of the output of nitrogen and phosphorus in UPA mode.Fish harvesting of IPRA mode accounted for 37.73%of the total output nitrogen,which was higher than that of UPA mode?35.07%?.Fish harvesting accounted for 25.50%of total phosphorus output more than UPA mode?20.78%?.In addition,the proportion of phosphorus expenditure in the water at the end of IPRA model cultivation is smaller than that of UPA model,which can reduce the pollution of the discharged water to the surrounding environment and has the characteristics of ecology,green and ecology.