Bacterial community structure diversity and environmental factors in the coastal shellfish culture area of Huangdao

Shellfish farming is an important part of China's aquaculture industry. With the continuous expansion of the scale of aquaculture, the unreasonable operation of the aquaculture industry has caused a greater burden on the environment, caused the change of microbial community structure in aquaculture water, and caused certain harm to the health of shellfish aquaculture. Meanwhile, it has also caused huge economic losses to the shellfish aquaculture industry, which seriously affected the sustainable development of the shellfish industry. In order to study the open aquaculture waters of offshore shellfish, the distribution of bacterial populations, the response of microbial community diversity to environmental factors and its relationship with the incidence of diseases in aquatic animals, we collected sea water samples from different locations in an open aquaculture water area in Huangdao from July to November 2019 to analyze different water quality factors (water temperature, salinity, pH, dissolved oxygen, chlorophyll a, ammonia nitrogen, phosphates, nitrates and nitrites), used high-throughput sequencing methods to analyze the differences in the microbial community structure and diversity of water samples and Chlamys farreri tissue samples in different months, and discussed the correlation between environmental factors and microbial community structure. The results showed that 42 phyla and 94 classes were detected in the bacterial community structure of water samples. It is composed of Proteobacteria, Bacteroides, Cyanobacteria, Actinomycetes, Firmicutes, etc. Among them, Proteobacteria is the dominant phyla, mainly including γ-Proteobacteria and α-Proteobacteria. The results of the diversity analysis of bacterial OTU levels in different months were November>September>July>October>August; the diversity analysis of Vibrio OTU level showed that the diversity of Vibrio increased first and then decreased, and the trend was consistent with the change of water temperature. The diversity of the culture area in August was higher than that of the control area. RDA analysis showed that the chlorophyll content (μg/L) and nitrite (mg/L) concentration had a significant impact on the species composition and community structure at the phylum level. Phosphate content (mg/L) and DO (mg/L) have a significant impact on the community structure of Vibrio. A total of 45 phyla were detected in the bacterial community structure of tissue samples, and the Tenericutes is the dominant phyla, mainly including Mycoplasma, which has a significant positive correlation with the phosphate content (mg/L). The results of the isolation and identification of the dominant bacteria of Vibrio showed that the dominant Vibrio in the culture environment from July to November were V. alginolyticus and V. harveyi. Studies have shown that aquaculture activities have a certain impact on the microbial community structure in the water by changing the content of chlorophyll and nitrite in the water. At the same time, changes in phosphate and DO have a certain impact on the community structure of the Vibrio genus. The results of this study can provide certain theoretical support for the occurrence of shellfish diseases.