48 



well-known In Europe and North Aaerlca. 



However, aany other variables in addition to teq>erature mediate the 

 survival of newly-released organisas. Even when and where tea|>eratures 

 are slailar between the ballast water and receiving waters, salinity, 

 oxygen, light, food, and aany other biological and ecological factors 

 ■ay be inhospitable or limiting. A very small number of all species 

 released over a given period of time (for example, over several years) 

 by most transport mechanisms (including ballast water) actually become 

 established in new regions. As demonstrated by the zebra mussel and 

 many other important invaders, however, only one successful invader is 

 required to dramatically alter the environment and impact human society. 

 Sediment (clay, mud, and fine sand) be taken aboard with water. These 

 materials then settle In ballasted cargo holds and in ballast tanks. In 

 tanks these sediments may accumulate as a mud layer, while in holds such 

 materials may be combined with residual cargo, such as woodchip fibers 

 and fragments, to form a bottom "sludge". In ballast tanks sediments 

 may accumulate as a mud layer. Australian studies report the presence 

 of shrimps, crabs, worms and many other marine organisms in these 

 sediments, and further report that over 65 percent of cargo vessels may 

 carry significant amounts of sediments in their ballast systems. These 

 sediments may also contain the abundant resting stages (cysts) of 

 microscopic toxic marine plants (dinoflagellates, members of the 

 phytoplankton) that can cause harmful algal blooms such as red tides. 

 Host vessels keep some tjrpe of record of ballasting operations, but 

 there is no uniform industry standard. 



Based upon NABISS estimates of both acknowledged and unacknowledged 

 water an estimate of the amount of ballast water arriving in the O.S. in 

 vessels from foreign ports (based upon 1991 data) is as follows: 

 There are 226 U.S. ports that receive vessel traffic from foreign ports; 

 we examined in detail 21 of the largest of these ports. The amount of 



