By Janet Raloff
While in port, shipping vessels often suck huge quantities of water into their ballast tanks to replace the stabilizing weight of cargo they’ve off-loaded. Along with this water comes abundant aquatic life, such as mussels and crabs, which journey with the ships—often crossing entire oceans—until the ballast is dumped in preparation for loading new goods.
Largely ignored in this lively exchange are microbes. A new study finds that releases of ballast water dump huge quantities of bacteria and viruses into ports around the globe.