Effect of different doses of trichloroisocyanuric acid on aquaculture pond water

Understanding the bacterial dynamics in aquaculture ponds is imperative for the assessment of disinfection efficiency and regulation of subsequent pond ecosystems. In this study, the objective was to evaluate the impact of trichloroisocyanuric acid (TCCA) (0.135 mg/L, LG; 0.405 mg/L, HG) on the water quality index, heterotrophic bacteria, microbial community and ecological function. Nine separated artificial customized tanks were inserted into the pond sediment to form relatively independent pond bodies with similar environments. 16S rRNA gene amplicon sequencing was used to evaluate the dynamics of bacterial relative abundance within 192 h. Furthermore, the functional composition of the microbial community was inferred. The results indicated that both doses of TCCA had little influence on water quality. The residual chlorine was lower than the detection limit (0.03 mg/L) in the both LG and HG within 30 min. The bacterial inactivation rate was 65.04% in the HG compared with the control group within 1 h., whereas the number of heterotrophic bacteria increased to 1.26 × 105 cfu/mL at 24 h. and 4.53 × 105 cfu/mL at 48 h., 6.03 and 6.38 times higher than the CG (P < 0.05), respectively. The TCCA in the HG significantly decreased the microbial diversity and changed the relative abundance of the pond at 24 h. and 48 h. There were 28 and 35 significantly different genera between the CG and HG (P < 0.05), and the relative abundance of Bacillariophyta in the HG was significantly higher than that in the CG at 24 h. and 48 h. (P < 0.05).There were 7 and 4 significantly different functions (except other function) between the HG and CG (P < 0.05) at 24 h. and 48 h., respectively. The results indicated that the active chlorine disappeared immediately after using TCCA, 0.405 mg/L active chlorine had a strong influence on the heterotrophic bacteria, microbial community and function, and the effect lasted for 96 h., whereas 0.135 mg/L TCCA usage had little influence on the pond water.