Sterilizing That Blasted Ballast

• Mario Tamburri

In the dank bowels of the ship, a million microbes squirm and writhe. Their watery cradle — the ballast — plays a central role in balancing the weight of giant cargo ships that regularly shuttle back and forth between the world's oceans.

Invisibly ferried from port to port, the hitchhiking larvae, phytoplankton and bacteria pose a costly threat. If flushed into the wrong environment, these aliens could very well take over ecosystems.