STEMMING THE TIDE
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The April 13, 2002, Science News cover story was Stemming the tide;
killer technologies target invading stowaways – ballast water responsible for
many marine pests. This article was by Ben Harder. He described how ballast
water from ocean ships created problems for native wildlife. The problems are
caused by exotic creatures hitching a ride on the ship. Then when the ballast
water is dumped somewhere else, the non-native organisms competed with the
existing organisms.
Harder detailed some of the technologies that were being tried to remove the
ecological pests. He said that the pests include zebra mussels, green crabs, sea
lampreys, and round gobies. One method has been to exchange fresh water with sea
water. Harder interviewed Hugh J. MacIsaac of the University of Windsor.
MacIssac noted that one in every thousand organisms still live after the
exchange. This is enough for the pests to seed an invasion so other methods need
to be used.
Harder mentioned that many groups are researching ways to combat the problem.
He said that filters have been tried but get clogged or don’t remove real small
living things. Another tactic is to use centrifugation, or fast spinning of the
water to make the living things sink to the bottom. A third tactic is to use
ultraviolet radiation (UV) to kill small organisms. The results said that a
combination of methods such as screening and UV radiation may be the most
effective.