Effects of Circulation Rate on Water Quality and Bacterial Community Composition in a Recirculating Aquaculture System for Litopenaeus vannamei
In order to investigate effects of circulation rates on water quality and bacterial commu-nity structure of a recirculating aquaculture system for Litopenaeus vannamei,three different water circulation rates,LC(daily circulation rate of 10),MC(daily circulation rate of 15)and HC(daily circulation rate of 20),were set and run for 33 days.The changes of shrimp growth performance,water quality and bacterial community composition were analyzed during the study period.The results showed that the highest concentrations of LC,MC,and HC were 2.48,2.07,and 1.89 mg·L-1,respectively,during shrimp recirculating water aquaculture.The stud-y demonstrated that the removal efficiency of the system for nitrite concentration was accelerated with the increase of the water recirculation rate.The diversity of biofilm microorganisms de-creased with the increase of water circulation rate.The survival rates of shrimp in LC,MC and HC groups were 61%,73.6%and 79%,respectively.Proteobacteria and Bacteroidetes were the two dominant phylum in the experimental systems,and the relative abundance of Proteobacteria in LC,MC,and HC groups was 32.34%,36.91%,and 38.44%,respectively.The proportion of Proteobacteria and Bacteroidetes increased with the increase of circulation rate.The nitrifying bacteria were mainly Nitrosomonas,Nitrococcus,and Nitrospira.A high recirculation rate wa-ter recirculation system was better for water quality and shrimp survival.
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