Alien stowaways

US Coast Guard officials plan to test the ballast water in all ships entering
US waters in an attempt to discover whether they are introducing alien marine
species into coastal ecosystems. Before approaching the US, ships are asked to
flush their ballast tanks with water from the relatively lifeless open ocean, to
remove stowaway organisms. But no one knows how many vessels are following these
voluntary guidelines. “We want to identify patterns to see if there is a glaring
need to make it mandatory,” says Chris Friese of the US Coast Guard’s Office of
Response in Washington DC.