Bacterial community composition and diversity in the ballast water of container ships arriving at Yangshan Port, Shanghai, China.

Ballast water is a major vector of invasion by protozoans and metazoans. Bacterial invasion is less-well understood. We surveyed the bacterial diversity of ballast water from 26 container ships arriving at the Yangshan Deepwater Port, Shanghai, China during 2015-2016. We characterized the ballast microbiome using high-throughput sequencing (HTS) based on V4-V5 region of 16S rRNA genes. We simultaneously monitored physicochemical parameters of the ballast water, including temperature, pH, dissolved oxygen (DO), salinity, turbidity, total suspended solid (TSS), particulate organic carbon (POC), NO2, NH4, PO4. Proteobacteria was the dominant phylum, comprising more than 50% of the OTUs of almost all vessels, followed by Bacteroidetes (12.08%), Actinobacteria (4.86%) Planctomycetes (3.24%) and Cyanobacteria (1.95%). The relative abundance of Cyanobacteria differed among vessels. It was negatively correlated with temperature, NO3, pH, TSS, PO4, and turbidity and positively correlated with NH4, POC. The genus Synechococcus was the most common Cyanobacteria in our results. Escherichia coli were relatively rare; they are indicator-species of D-2 standards published by the IMO. The relative abundance of the genus Vibrio ranged from 0.003% to 24.88% among different vessels. Our results showed that HTS was able to profile the bacterial communities in ballast-waters, even when the approach was restricted by technical and other obstacles.

Effects of holding time on the diversity and composition of potential pathogenic bacteria in ship ballast water.

Ballast water is a common vector for the transport of invasive species to new marine and aquatic environments. We used a metagenomics approach to examine the diversity and composition of potential pathogens communities in ballast water from ships in the route of China- Southeast Asia (CSEA). 16 kinds of potential pathogenic genus were detected in the ballast water. Interestingly, the ballast holding time had an important effect on the distribution of potential pathogens in ballast water. The abundance of Pseudoalteromonas in the longer ballast water holding time was less than the shorter ballast water holding time. Bacteroides had completely disappeared in the long ballast holding time samples. Moreover, The Shannon index of samples with longer ballast water holding time (1.80 ± 0.07) was higher than those with shorter ballast water holding time (0.83 ± 0.13). The potential pathogenic genus (Arcobacter, Aeromonas, Enterobacter and so on) lived in the long ballast holding time vessels had more diversity. Besides, the total suspended solids (TSS), total organic carbon (TOC) and particulate organic carbon (POC) had a strong positive correlation with most potential pathogens in the ballast water, while the dissolved oxygen (DO) had a clear negative correlation with the potential pathogens in the longer ballast holding time samples. In conclusion, these results provide detailed descriptions of the characteristics of the potential pathogens present in ballast water, document significant potential pathogens diversity, and indicate the importance of ballast holding time for potential pathogens lived in ballast water.