Study On The Purification Of Aquaculture Wastewater By Myrmecia Incisa And The Improvement Of The Growth Of Brachionus Calyciflorus

As a large aquaculture country,China’s freshwater aquaculture output value accounts for more than half of the national fishery output value.With pond and reservoir aquaculture as the main aquaculture methods,China produces aquaculture wastewater containing a large amount of nitrogen and phosphorus every year,posing a significant threat to the ecological environment of the surrounding water bodies of aquaculture sites.However,nitrogen and phosphorus in aquaculture wastewater are also essential nutrients for the growth of microalgae and other organisms.Therefore,if the aquaculture wastewater is properly utilized,the biological transformation of the aquaculture tail water can be achieved.Compared with common aquatic organisms used to treat aquaculture wastewater,the growth cycle of microalgae is shorter,which allows us to screen microalgae with good adaptability to aquaculture tail water in a shorter time.At the same time,microalgae can also produce diverse high-value products during the growth process,such as carotenoids,arachidonic acid(Ar A),and so on.Microalgae,as a botanical source of these high value products,have higher safety compared to common animal sources.In the current research results,Chlorella sp.and Scenedesmus sp.have been used to treat urban domestic sewage and livestock and poultry farm sewage.In this study,Ar A-rich Myrmecia incisa with high nitrogen utilization efficiency were selected to treat aquaculture wastewater,and the harvested algal liquid was used to feed Brachionus calyciflorus.Brachionus calyciflorus is a high-quality feed for aquatic animal seedlings,and there is a strong correlation between its growth and reproduction and its feed.However,there are problems with low peak population density and short duration in culture.The Ar A rich content in Myrmecia incisa has similar physiological effects to EPA.which is commonly used to improve the growth of rotifers.However,both the biomass and the Ar A content in cells of Myrmecia incisa are higher than those of Nannochloropsis oceanica and its EPA content.Therefore,it is feasible to select Myrmecia incisa to replace Nannochloropsis oceanica as the feed for Brachionus calyciflorus,which not only purifies the aquaculture wastewater,but also improves the growth status of high-quality aquatic bait.The main content of this study was to explore the adaptability of Myrmecia incisa on aquaculture wastewater and the purification effect of aquaculture wastewater,and to detect the content of Ar A in Myrmecia incisa after treatment.To investigate the effect of harvested green algae on the growth of Brachionus calyciflorus who was fed on it.The main conclusions are as follows:(1)This study proved that Myrmecia incisa with a good adaptability and purification effect on aquaculture wastewater.The aquaculture wastewater had the ability to fully support the growth of Myrmecia incisa without hindering the accumulation effect of cell density of Myrmecia incisa.The removal rates of total nitrogen and total phosphorus from aquaculture wastewater by Myrmecia incisa may reach 99.94% and 97.47% respectively,and nitrogen elements were removed from aquaculture wastewater at a faster rate during the growth period,leaving some newly added algae cells in a low nitrogen environment,contributing to the accumulation of Ar A,improving the production and yield of Ar A,and increasing the content of Ar A in Myrmecia incisa TFA by 13.31% to 26.45%.(2)This study demonstrated that Myrmecia incisa can significantly promote the reproduction of Brachionus calyciflorus,increasing the upper limit of population density,the upper limit of daily net growth rate of population density,and the upper limit of daily net growth rate of number of eggs carried by Brachionus calyciflorus to 163.67 ind/m L,86.40%,23.67 ind/m L,and 408.33%,respectively,with an improvement effect of 2.4,3.28,6.62,and 0.7 times that of Nannochloropsis oceanica.Increased the stability of highdensity Brachionus calyciflorus production.To sum up,this study combines the purification of aquaculture wastewater with the high-density and stable production of Brachionus calyciflorus.By treating the aquaculture wastewater with Myrmecia incisa,nitrogen and phosphorus in the aquaculture wastewater are ultimately purified,and a high Ar A content of Myrmecia incisa was obtained.Therefore,aquaculture wastewater may be used as a new type of culture medium for Myrmecia incisa,while maintaining the ecological environment of the water around the aquaculture site,it may also promote the production of high-quality aquatic bait through Myrmecia incisa with high Ar A content,thereby assisting the development of the aquatic industry and providing a technical route for future green production in the aquatic industry.