The text on this site is presented as an archival version of the script of "Ocean Planet," a 1995 Smithsonian Institution traveling exhibition. The content reflects the state of knowledge at the time of the exhibition, and has not been updated.

Biological Roulette

For centuries, people have transplanted locally native marine species to new areas. In some cases the introductions are intentional: animals are imported for fish farming. Most introductions are unintentional and unfortunate. In their new homes, hitchhikers and stowaways often turn into troublemakers §.

Ballast water brings unwanted passengers aboard §. Ships take on ballast water to adjust their position in the water or to improve maneuverability and stability. When ships drain ballast water, plants and animals picked up elsewhere may survive and move into new territory.

Click on the wheel to see how some alien species were introduced, and what happened

Alexandrium catenella
To: Australia
Effect: Caused red tides, contaminated seafood
How introduced: Stowaway brought in ballast water
Illustration © Tim Phelps


Zebra mussels muscle in in the Great Lakes §

The most famous or infamous ballast-water stowaway is the zebra mussel. Originally from Europe, it now flourishes, to say the least, in the Great Lakes: 700,000 zebra mussels may occupy only 1 cubic yard. Mussel damage to industries, public utilities, navigation, boating, and sport fishing could total $5 billion by the year 2000.

Zebra mussels clog a water intake pipe, Detroit Edison's Monroe Plant
photo © Ron Peplowski, courtesy of Detroit Edison

More information:

Asian clams take the advantage in San Francisco Bay §

In 1986, just after a flood lowered populations of native San Francisco Bay clams and mussels, the Asian clam, Potamocorbula amurensis, arrived in ballast water. Within two years, there were more than 12,000 Asian clams per square meter in some areas. Now the Asian clam population, along with 150 other introduced species, could alter the bay's entire food web.

Golden Gate Bridge, San Francisco Bay
photo © David W. Hamilton/The Image Bank


Guidelines get rid of stowaways

In 1991, the International Maritime Organization (a United Nations agency) developed voluntary guidelines for ballast water. All participating major and medium-sized shipping nations will take measures to control the spread of alien species. §

Algal bloom

International Maritime Organization guidelines advise ships to avoid taking on ballast water in heavily silted areas or waters with algal blooms. §
photo © Norbert Wu

Other Resources:

Ocean Planet Exhibition Floorplan

gene carl feldman ( (301) 286-9428
Judith Gradwohl, Smithsonian Institution (Curator/Ocean Planet)