Reducing Carbon Input Improved the Diversity of Bacterial Community in Large-Scale Biofloc Shrimp Culture Facilities

In this study, a group of large-scale biofloc shrimp culturing facilities were designed. The bioflocs were domesticated by continuously reducing the ratio of carbon to feed. The bacterial community diversity on the 20th, 40th, 60th, and 80th days was analyzed by high-throughput sequencing technology. The results showed that the biofloc content (0 similar to 16.8 +/- 4.3) mL/L, TSS concentration (0 similar to 247.46 +/- 27.3) mL/L, total ammonia nitrogen concentration (0 similar to 0.28 +/- 0.052) mg/L, nitrite nitrogen concentration (0 similar to 4.13 +/- 1.42) mg/L, nitrate nitrogen concentration (108.57 +/- 19.6) mg/L were all within the safe concentration range of Litopenaeus vannamei. With the progress of reducing carbon input, the Chao1 index, the number of operational taxonomic units, and the Shannon index increased significantly. The number of OTUs of B80 (572.36 +/- 13.26) was significantly higher than that of B60 (489.69 +/- 12.97), B40 (423.35 +/- 18.46) and B20 (407.67 +/- 15.65) (p < 0.05). The Chao1 index of B80 (768.58 +/- 36.96) was significantly higher than that of B60 (646.8 +/- 52.53), B40 (569.7 +/- 46.53) and B20 (516.3 +/- 21.35) (p < 0.05). The Shannon index of B80 (5.63 +/- 0.16) was higher than that of B60 (4.85 +/- 0.13), B40 (4.68 +/- 0.21) and B20 (3.65 +/- 0.22), with significant difference (p < 0.05). At the end of the experiment, the domestication formed a micro-ecosystem with Proteobacteria as the carrier (46.98 +/- 15.82%), Chloroflexi as the skeleton (2.2 +/- 0.36%), Nitrospirae (1.35 +/- 0.26%) as the main water treatment functional bacteria, and other bacteria as auxiliary nitrogen and phosphorus removal; At the genus level, unclassified_f_Rhodobacteracea (22.97 +/- 3.82%), Ruegeria (10.35 +/- 1.26%), Muricauda (5.73 +/- 0.61%), Algoriphagus (3.75% +/- 0.85%) and Nitrospira (1.56 +/- 0.56%) are the dominant bacteria. Under the synergistic effect of the above bacteria, the biofloc system remains relatively stable. The survival rate and unit yield of shrimp were (65.32 +/- 6.85)% and (4.15 +/- 1.58) kg/m(3), respectively.

Automated summary

In this study, a group of large-scale biofloc shrimp culturing facilities were designed, and the bioflocs were domesticated by continuously reducing the ratio of carbon to feed. The results showed that with the progress of reducing carbon input, the bacterial diversity of the biofloc system increased significantly. The domestication formed a relatively stable micro-ecosystem, resulting in a high survival rate and unit yield of shrimp.