A communication in Nature for November 2 by a group of investigators from Maryland
and Virginia describes the possible risk from pathogenic micro-organisms distributed
into harbours by the discharge of ballast water by commercial vessels. Ships
have used water as a stabilising ballast since the 19th century and have been
in the habit of discharging it both in ports of call and en route at sea.
Samples of ballast water taken from vessels arriving in Chesapeake Bay were
examined for their content of bacteria, virus-like particles and, in particular,
cholera vibrios. Plankton samples from all the ships examined contained significant
concentrations of Vibrio cholerae serotypes 01 and 0139, with a preponderance
of the 01 strain. The distribution of cholera vibrios by ballast is an important
factor in the colonisation of coastal ecosystems by the organism, and if a novel
genotype should arrive in a port local conditions may encourage its firm establishment.
Many micro-organisms have the ability to tolerate a wide range of temperatures
and salinities, and might constitute a threat to health. Although concern has
been aroused by the possible effects of invertebrates brought in by shipping
on local conditions, little attention has been paid hitherto to the parallel
role of pathological micro-organisms. Further research is deemed advisable.