| Water eutrophication is a major pollution faced by the aquatic environment of shrimp cultivation,and excessive nitrogen source input is one of the main causes of water eutrophication.Therefore,how to effectively deal with the excessive nitrogen source in aquaculture water to maintain an environment with healthy water quality has become a major issue that the shrimp aquaculture industry needs to address.Microalgae and bacteria play an important role in maintaining the dynamic balance of aquaculture ecosystem,accelerating the material circulation and purifying the aquaculture water quality.For one thing,bacteria and microalgae can effectively absorb and utilize the excess dissolved nitrogen in shrimp pond,reduce the eutrophication degree of water,which conducive to maintaining a healthy water quality environment.For another,the carbon dioxide produced by bacteria degradation of organic matters can provide carbon source for algae,and the oxygen released by photosynthesis of algae can promote bacterial respiratory and metabolism,which complement each other.Nitrogen pollution in aquaculture wastewater can be effectively treated by bacteria-algae symbiotic system.Therefore,the scientific construction of bacteria-algae system may become a new strategy to improve the water quality environment of shrimp breeding and develop green and healthy farming.In this research,the absorption of NH4+-N,NO3--N and Urea-N by a combined system of Brevibacillus laterosporus and Thalassiosira weissflogii under different temperature,salinity and light levels were studied.The optimal temperature,salinity,and light conditions for absorption of NH4+-N,NO3--N and Urea-N by the bacteria-algae system were determined by orthogonal experiments.The results are as follows.?1?Effects of temperature,salinity and light on NH4+-N absorption of the bacteria-algae system.Temperature,salinity and light intensity have a significant effect on the absorption rate of NH4+-N?P<0.05?.The absorption rate of NH4+-N by the bacteria-algae system increased with the rise of temperature,and the absorption rate was higher at 25?35?,which was667.98?818.45?g·g-1·h-1.The maximum absorption rate was 400.26?g·g-1·h-1 at salinity of20.In the range of experimental light,the absorption rate of ammonia nitrogen by bacteria-algae system increased with the increase of light,and reached the maximum at 8000 lx,which was 562.15?g·g-1·h-1.According to the orthogonal experimental analysis,the best conditions for the absorption of NH4+-N by the bacteria-algae system was 25?,salinity 25,and 4 000 lx.The average absorption contribution rate of B.laterosporus and T.weissflogii to NH4+-N in combined system were 7.5%and 92.5%under the experimental temperature range,19.1%and 80.9%under the experimental salinity range,and 9.6%and 90.4%under the experimental light range respectively.T.weissflogii contributes to the absorption of NH4+-N in the bacteria-algae system.?2?Effects of temperature,salinity and light on NO3--N absorption of the bacteria-algae system.Temperature,salinity and light intensity have a significant effect on the absorption rate of NO3--N?P<0.05?.At the temperature of 35?,the maximum NO3--N absorption rate of bacteria-algae system was 143.86?g·g-1·h-1.At the salinity of 35,the maximum absorption rate of the bacteria-microalgae combination to NO3--N reached 22.95?g·g-1·h-1.The absorption rate of NO3--N by the bacteria-algae system decreased with the increase of light intensity,and the maximum absorption rate reached 7.37?g·g-1·h-1 at 500 lx.According to the orthogonal experimental analysis,the best conditions for the absorption of NO3--N by the bacteria-algae system was 30?,35 in salinity,and 500 lx.The average absorption contribution rate of B.laterosporus and T.weissflogii to NO3--N in combined system were11.2%and 88.8%under the experimental temperature range,10.8%and 89.2%ender the experimental salinity range,and 23.1%and 76.9%under the experimental light range.T.weissflogii contributes to the absorption of NO3--N in the bacteria-algae system.?3?Effects of temperature,salinity and light on Urea-N absorption of the bacteria-algae system.Temperature,salinity and light intensity have a significant effect on the absorption rate of Urea-N?P<0.05?.The rate of absorption of urea by the bacteria-algae system increased first and then decreased with the increase of temperature.The absorption rate was higher at25?35?,which was 313.81?351.68?g·g-1·h-1.The maximum absorption rate by the bacteria-algae system was 264.21?g·g-1·h-1 at salinity 25.The absorption rate of urea by the bacteria-algae system increased with the increase of light intensity,and the absorption rate was higher at 4000?8000 lx,which was 296.13?321.52?g·g-1·h-1.According to the orthogonal experimental analysis,the best conditions for the absorption of Urea-N by the bacteria-algae system was 30?,salinity 35,and 8000 lx.The average absorption contribution rate of B.laterosporus and T.weissflogii to Urea-N in combined system were2.4%and 97.6%under the experimental temperature range,14.6%and 85.4%under the experimental salinity range,and 6.4%and 93.6%under the experimental light range.T.weissflogii contributes to the absorption of Urea-N in the bacteria-algae system.In conclusion,the bacteria-algae system of laterosporus and T.weissflogii can achieve effective absorption of excess NH4+-N and Urea-N under high temperature,high salinity,and strong light environment,and achieve effective absorption of excess NO3--N under high temperature,high salinity,and low light environment.Therefore,it may have a broad application prospect in improving the water quality of shrimp culture ponds in South China. |
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