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Invasive Species Transport !01178_lr.jpg|width=477,height=403!Sediment in a ballast tank; this sediment can host aquatic invasives. Source: NOAA
For international ships, the current wisdom is that the country should require that in order to come into port, the ballast water must be exchanged at sea, past the continental shelf. The idea behind this is that the a species can only establish itself if its biological needs are met and changes in salinity and water temperature as found between fresh or estuarine waters and open ocean are great enough to kill most potential invasives.(Portland State University, 2006)
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