Application of eDNA method to analyze bacterial community structures in the recirculation aquaculture systems of Litopenaeus vannamei

One of the main focuses in microbial ecology is the analysis of microbial communities in water, especially concerning bacteria. The results of the analysis related to the abundance of bacteria will be essential knowledge for the development of aquaculture, especially those relating to the dynamics of pond water quality. This study aims to analyze the total abundance of bacteria and water quality dynamics in the water of Litopenaeus vannamei aquaculture that applies a recirculation system. The study was conducted for three months on a concrete pond plot with an area of 2500 m2. Samples of bacterial abundance were taken from pond water, while water quality checks were carried out at ponds and pond outlets. Sampling was carried out at weeks 1, 3, 5, and 8 during the cultivation phase. Bacterial abundance was calculated using Environmental DNA (eDNA), which refers to DNA extracted from the environment without isolating the target organism. The water quality parameters observed were pH, conductivity, DO, turbidity, temperature, and salinity. This study suggested that the abundance of bacteria from the first to the 8th week were 15.3x107; 17.1x107; 36.6x107; and 35.4x107, respectively. Moreover, DO ranged from 3.2 ppm to 7.6 ppm; temperature ranged from 30 °C to 33.3°C; turbidity raged from 12 NTU to 57 NTU; salinity ranged from 19 ppt to 24 ppt; conductivity ranged from 2.93 s/m to 3.54 s/m, and pH ranged from 6.6 to 7.0. This study indicates that the recirculation aquaculture system in Lamongan, East Java may obtain the optimum water quality and controlling the abundance of bacteria to support the aquaculture of Litopenaeus vannamei.