Baltimore Harbor

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Alien species? That's right. And they are invading our waters, rearranging marine life in the seas as they enter ports via the ballast water of international cargo ships. Could they be a threat to marine ecosystems?

In many U.S. ports, foreign plants or animals are introduced to new homes where they flourish, hungrily gobbling up their native neighbors who are not prepared to deal with them. These "trespassers" are popping up all over the world.

Maybe you've heard of them: European Green Crabs, and other "trespassers" colonizing under the waters of the San Francisco Bay or the many alien species found in the Chesapeake Bay.

RADIO EXPEDITIONS investigates these "alien species." Take a trip by boat to test sites on the Chesapeake Bay, where new species arrive via international ships. researcher Greg Ruiz explains the nature of these new forms of marine life. NPR's Lynn Neary then follows scientists to Baltimore Harbor to examine arriving ships whose ballasts are loaded with alien passengers.

The Green Crab (Carcinus Maenas), one of the better-known invaders of the east and west coasts, was probably first introduced to the United States via Long Island Sound. The species took up residence in the ballast water of a boat coming from Europe in the late 18th century. It was a very successful invader, and has adapted well, surviving major environmental changes throughout the 20th century. The Green Crab is a voracious predator, and, if you look at its availability and its capacity to eat native species, its potential impact is quite large.

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