Environmental Engineering Reference
In-Depth Information
UNEP. Most soon die off, and most of the rest are harmless. But the risk of a new zebra mussel or
Mne-
miopsis
jellyfish or disease infestation continues.
An effective invasion is most likely to occur if the journey is not so long that the alien dies en route
and not so short that it may already be present locally. Invasions are also more likely if the starting point
is in warm water, which usually contains more species, and if the water at both ports is of similar tem-
perature and salinity. That entails busy tropical ports handling long-distance cargo, says Bernd Blasius
of the University of Oldenburg in Germany. After mapping more than three million ship journeys and
assessing the species migration possibility presented by each, he calculated that twenty major ports carry
39 percent of the total risk of invasions. These include San Francisco Bay, New York City, Los Angeles,
Hong Kong, Singapore, and Durban, along with the Suez and Panama Canals. The journeys most likely
to deliver aliens are those of between five thousand and seven thousand miles—roughly the distance
between busy Asian ports such as Shanghai and Singapore and the west coast of the United States.
6
The
prediction matches data from ports that have known problems, such as San Francisco Bay, where the
majority of inhabitants are alien species, whose names often tell their own story. Scoop water from the
bay and you may find Chinese mitten crabs, New Zealand sea slugs, or Japanese gobies—all brought by
ballast water.
So, many ask, why the delay in addressing the threat? It is a good question. A treaty agreed on at
the UN's International Maritime Organization (IMO) in 2004 required most international cargo ships
and tankers to install disinfection kits to kill off biological stowaways.
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But, as of late 2014, it had not
been ratified by sufficient nations to come into force. The technology is available. The IMO has certified
more than twenty commercial treatment systems, involving various combinations of filtration, irradi-
ation, ozone dosing, heat, electrolysis, and biocides. The holdup seems to be the cost. At up to $500,000
of equipment for each of the biggest vessels, we are talking about a billion dollars or more.
But there should be another concern, says one prominent marine biologist, speaking on condition of
anonymity. Some methods of cleaning up ballast water could actually increase the risks—in particular
from bacteria. The warm and quiet conditions inside ballast tanks can act as incubators for colonies of
bacteria, and some treatment systems could make matters worse by killing off the things that eat the bac-
teria, like copepods, while leaving the bacteria unscathed. Moreover, the dead plankton floating around
in the tanks after the treatment could provide a valuable source of food for the bacteria.
“You could end up with ten or one hundred times more bacteria, as a result of the wrong sort of
treatment,” he told me. Sitting in the tanks at higher concentrations, the bacteria would also be more
likely to turn into new strains through genetic exchanges. “You could be creating new diseases,” he said,
especially if you treat at the start of a voyage but not again before discharge. With no present IMO re-
quirements to measure bacteria in the tanks during or at the end of a voyage, it is a disaster waiting to
happen, he believes.
It may not be so bad. Billions of bacteria and viruses already travel the world in ballast water. Most
of these microbes may be present so widely in the oceans that moving them around makes little differ-
ence to the threat they pose. But Fred Dobbs, a marine microbiologist at Old Dominion University in
Norfolk, Virginia, says, “The bacterial and viral diversity in ballast water is absolutely unknown.” And
the story of cholera reaching Peru suggests a significant, if infrequent, risk.
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You don't need ships to create an alien invasion at sea. During the autumn of 2013, I joined a tour of the
Monaco Oceanographic Museum. The museum was established by the late French marine adventurer
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