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.