Analysis of Microbial Community Structure in the Coastal Waters of Island Cities: Based on High-Throughput Sequencing...

Coastal water microbial communities are highly diverse and often undergo changes with variations in environmental conditions. This study focuses on the seawater around Pingtan, utilizing Illumina MiSeq sequencing (San Diego, California, United States) and bacterial cultivation techniques to analyze the abundance and relative composition of planktonic bacterial communities.

On May 26, 2023, seawater samples were collected at Liushui Port, Guanyin'ao Port, and Qianbian'ao Port in Pingtan County. At each sampling point, random samples were taken at 500 meters, 1000 meters, and 1500 meters, and relevant physicochemical factors were measured. Samples were processed using a suction filtration system to obtain nine filters, grouped into O1, O2, and O3 based on the offshore distance of the sampling points. Subsequently, total seawater bacterial sequencing was conducted. The remaining seawater samples were centrifuged for bacterial cultivation and identification. Alpha-diversity indices, including species coverage, species diversity indices (Shannon-Wiener and Simpson indices), richness estimates (Chao1), and abundance-based richness estimates (ACE), were calculated to assess the diversity of planktonic bacteria in seawater. Beta-diversity was employed to evaluate differences between samples. Statistical analysis was performed using the R software (R Foundation for Statistical Computing, Vienna, Austria).

The mean α-diversity indices for the O1 group were 345 OTUs, Chao 420, Ace 403.12, Shannon index 3.34, and Simpson index 0.11. In the O2 group, the values were 451 OTUs, Chao 494.08, Ace 491.46, Shannon index 3.34, and Simpson index 0.07. The O3 group exhibited values of 430 OTUs, Chao 467.99, Ace 465.40, Shannon index 3.51, and Simpson index 0.09. At the phylum level, in all groups, Proteobacteria were the most abundant phylum (55.32-77.74%). In the O1, O2, and O3 groups, the dominant genus was Vibrio, constituting 16.64%, 8.12%, and 13.77%, respectively. A total of 15 different bacterial species, comprising 57 strains, were successfully cultured from seawater bacterial cultivation. The findings suggest significant differences between the bacterial communities of O1 and O2 in ocean bacterioplankton.

The marine bacterial community exhibits a high abundance of bacterial taxa, including Proteobacteria, Cyanobacteria, and Bacteroidetes. The most prevalent genera are Vibrio, Pseudoalteromonas, and Candidatus_Pelagibacter. Importantly, the composition of bacteria varies with different nearshore distances.