Every minute of every day, what ecologist James Carlton calls a global "conveyor belt" redistributes ocean organisms. It’s a planet wide biological disruption that scientists have barely begun to understand.
Dr. Carlton—an oceanographer at Williams College in Williamstown, Mass. —explains that, at any given moment, "there are several thousand [marine] species [traveling].., in the ballast water of ships. " These creatures move from coastal waters where they fit into the local web of life to places where some of them could tear that web apart. This is the larger dimension of the infamous invasion of fish destroying, pipe-clogging zebra mussels.
Such voracious invaders at least make their presence known. What concerns Carlton and his fellow marine ecologists is the lack of knowledge about the hundreds of alien invaders that quietly enter coastal waters around the world every day. Many of them probably just die out. Some benignly
A. being moved to new environments
B. destroying the planet
C. succumbing to the zebra mussel
D. developing alien characteristics
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