Bacterial Diversity in Ships’ Ballast Water, Ballast-Water Exchange, and Implications for Ship-Mediated Dispersal of Microorganisms

Using next-generation DNA sequencing of the 16S rRNA gene, we analyzed the composition and diversity of bacterial assemblages in ballast water from tanks of 17 commercial ships arriving to Hampton Roads, Virginia (USA) following voyages in the North Atlantic Ocean. Amplicon sequencing analysis showed the heterogeneous assemblages were (1) dominated by Alpha- and Gammaproteobacteria, Bacteroidetes, and unclassified Bacteria; (2) temporally distinct (June vs August/September); and (3) highly fidelitous among replicate samples. Whether tanks were exchanged at sea or not, their bacterial assemblages differed from those of local, coastal water. Compositional data suggested at-sea exchange did not fully flush coastal Bacteria from all tanks; there were several instances of a genetic geographic signal. Quantitative PCR yielded no <i>Escherichia coli</i> and few instances of <i>Vibrio</i> species. Salinity, but not ballast-water age or temperature, contributed significantly to bacterial diversity. Whether anthropogenic mixing of marine Bacteria restructures their biogeography remains to be tested

R script for data analysis

The code associated with the manuscript analysis is contained in `DataAnalysis.R’. This file contains the maximum likelihood analysis and produces the plots in the main text and supplement

complete data

All data used for analysis is contained in 'completedata.csv'. This file consists of 3 columns. The first 'x' is the natural log transformed value of the inoculum density. The second, 'y', is the binary score of population establishment (1- established; 0- failed to establish). The last column, 'treat', identifies the environmental treatment (1- high carbon, 2- low carbon, 3- low carbon with predation)