57 



Ecological Roulette: The Global Transport of 

 Nonlndlgenous Marine Organisms 



James T. Carlton and Jonathan B. Geller 



Ocean-going ships cany, as ballast, seawater that is taken on in port and released at 

 subsequent ports of call. Plankton sannples from Japanese ballast water released in 

 Oregon contained 367 taxa. Most taxa with a pleinktonic phase in their life cycle were found 

 in bjillast water, as were all major marine habitat and trophic groups. Transport of entire 

 coastal planktonic assemblages across oceanic Ijarhers to similar habitats renders bays, 

 estuaries, and inland waters among ttie most threatened ecosystems in the world. Pres- 

 ence of teixonomically difficult or inconspicuous taxa in these samples suggests that ballast 

 water invasions are already pervasive. 



Biological invasions are a great threat to 

 the integrity o( rutural communities of 

 plants and animals and to the preservation 

 of endangered species (1). Most invasion 

 studies have focused on terrestrial and 

 freshwater systems in which one or a few 

 successful invaders have had a catastrophic 

 impact on native species (2) . Island ecosys- 

 tems, such as New Zealand and the Hawai- 



J T Cartton, Maritime Studies Prograni, Wrtiiams 

 College. Mystic Seapon. Mysnc, CT 06355. and De- 

 partment ol Biology. Williams College, Wiliiamstown. 

 MA 01267 



J B Geller. Department of Biological Saerx»s. Uni- 

 versity ol Nortti Carolina at Wilmington. Wilmington. 

 NC 28403. 



ian Islands, have in particular been devas- 

 tated by the invasion of nonindigenous 

 species (l-i). Invasions in manne systems 

 have been less studied (4) . but are of such 

 magnitude that marine invasions may be 

 leading to profound ecological changes in 

 the ocean. 



Any mechanism for rapidly transport- 

 ing large volumes of water containing 

 plankton from shallow, coastal waters 

 across natural oceanic barriers has the 

 potential to facilitate massive invasions of 

 entire assemblages of neritic marine orga- 

 nisms. Such a mechanism exists in the 

 transport of ballast water and plankton by 

 ocean-going ships (5), a dispenal mecha- 



SCIENCE 



VOL. 261 • 2 JULY 1993 



