51 



8 



8Y8te« and the New Orleans region. 



Biological Invasions In aquatic envlronaents frequently have profound 

 ecological, econoalc, and social consequences. Not all Invasions have 

 striking negative effects: aome Invasions have had strong positive 

 economic inpacts (such as the edible Japanese llttleneck clan Venerupls 

 philippinarum . Introduced accidentally with comercial oysters in the 

 Pacific Northwest). However, the number of nonindigenous species that 

 have become predators and competitors, the number of Invading plankton 

 species that cause toxic algal blooms, and the number of invaders that 

 are parasites, pathogens, and other disease-causing agents of fish, 

 shellfish, and humans, set a striking stage for the need to manage the 

 means by which exotic species gain access to the United States. 

 A striking series of dramatic global ballast-mediated invasions have 

 occurred in the 19808 and continue steadily into the 1990s. The Great 

 Lakes have been invaded by the zebra mussel Dreissena and five other 

 species of European freshwater organisms; the New Jersey and 

 Massachusetts coasts have now been invaded by the Japanese crab 

 Hemigrapsus sanguineus : and California, Oregon, and Washington estuaries 

 have been Invaded by many species of Chinese and Japanese marine 

 organisms, including crustaceans, the Asian clam Potamocorbula 

 amurensis . In 1993 alone carnivorous Russian Jellyfish and carnivorous 

 New Zealand sea slugs were discovered in San Francisco Bay. Australia 

 was invaded by Japanese dinoflagellates and has now been Invaded by 

 devastating waves of the Japanese seastar (starfish) Asterias amurensis 

 (a species that can be transported to America in ballast water), and the 

 Black and Azov Seas were invaded by American comb Jellyfish Hnemiopsie 

 leidvl. leading to the virtual collapse of the anchovy fishery in the 

 Azov Sea. A global epidemic of phytoplankton blooas is now occurring and 

 ballast water has played a clear role in some of these events. Scores of 

 other invasions in the 1980s have been reported as well. Many of these 



