MICROBES HITCH RIDES IN BALLAST WATER
WebPosted Thu Nov  2 11:52:13 2000

WASHINGTON, D.C.--Large volumes of bacteria and viruses are being 
discharged into ports around the world. Researchers have found microbial 
organisms are travelling the globe floating in shipboard ballast water. 

 Scientists from the Smithsonian, the University of Maryland, and Old 
Dominion University are reporting in Thursday's Nature , ballast water 
discharges by the world's ocean-going ships, "create a long-distance 
dispersal mechanism for human pathogens." 

 They also say these waters may play an important role in the worldwide 
distribution of microorganisms as well as the epidemiology of waterborne 
diseases affecting plants and animals. 

 Scientists, governments and shippers alike have long known such 
discharges have unintentionally spread plankton, shellfish and fish from 
one body of water to another, sometimes with major impacts to the 
receiving ecosystem. 

 Researchers traced the invasion of zebra mussels in Canadian lakes to 
discharges of ballast water. 

 Lead researcher Gregory Ruiz, from the Smithsonian says though there is 
no reported evidence of outbreaks of human diseases from non-indigenous 
microbes in ballast water, the team's findings indicate the need for 
much greater concern than has been shown to this point. 

 The team wrote, "We know of no published estimates of microbial genetic 
diversity in ballast water, and the fate of microorganisms discharged 
from ballast tanks remains unknown." 

 Ruiz and his colleagues say the magnitude of the ongoing transfer, and 
the potential consequences for ecological and disease processes, merits 
attention from both invasion biologists and epidemiologists. 

 One example given in the study is that of vibrio cholerae , the 
bacterium that causes human epidemic cholera. It was detected in all 
ships tested. 

 The team said that while this organism and other potential pathogens are 
normal constituents of coastal waters in the United States, they do not 
ordinarily occur in high enough concentrations to cause human health 
problems. 

 But, they warn, with expanding world trade and increasingly larger 
vessels moving among international ports, the impact of non-indigenous 
microorganisms could be profound. 

 The study authors write that laboratory observations have, "revealed 
that some bacteria are viable upon arrival, and that their release 
creates an opportunity for the colonization of coastal ecosystems." 

 Ruiz says management efforts are underway to limit the risk of 
non-indigenous species in such discharges. These include exchange of 
ballast water at sea, the installation of filtration systems, and heat 
and chemical treatments. 

 But the transfer of microorganisms may be especially difficult to 
control with such options because of their small size, their tolerance 
to high temperatures and their ability to form resting stages. 

 
Copyright © 2000 CBC All Rights Reserved