Biologists study options for managing ballast water invasions

by William G. Gilroy

A new study by biologists from the University of Notre Dame examines the best options for managing biological invasions from ballast water in ships.p. In the paper, which will appear in an upcoming issue of the Proceedings of the Royal Society, David M. Lodge, a professor of biological sciences, and John M. Drake, a doctoral student, identify global hot spots for biological invasions from ballast water.p. “For the first time ever, we were able to give an idea of the areas where we should be paying attention,” Lodge said.p. Biological invasions from ballast water are a leading environmental concern in navigable freshwater and marine ecosystems. The invasions result from ships taking on ballast water that contains non-native species and then discharging that ballast water and the species in areas where they previously did not exist.p. “Although most of the tens of thousands of species that are transported don’t survive, the small fraction that do can be extremely troublesome,” Lodge said.p. Drake points out that scientists know virtually nothing about many of these species.p. “Some of these microscopic organisms are pathogens, such as cholera, and others cause red tides threatening fisheries and human health,” he said.p. A 2001 cholera outbreak at a port in Peru which infected 500,000 people and caused 4,000 deaths, is believed to have been started by a release of cholera in ballast water.p. Lodge and Drake’s analysis found that some areas known to have a large number of non-indigenous species, including the North American Great Lakes and the San Francisco Bay and Delta ecosystems, are nevertheless probably not among the most invaded areas globally. By contrast, global hot spots for invasions include large regions of Southeast Asia, northern Europe and the Mediterranean Sea, the researchers reported.p. Lodge and Drake also point out that changing patterns of ship traffic can increase or decrease the rate of invasions.p. The Notre Dame researchers also examined two different strategies for controlling ballast water introductions of invasive species. They compared the efficacy of building on-shore water treatment facilities at selected global hot spots or treating all individual ships. Their research shows that reducing the chance of individual ships causing invasion is more effective than attempting to eliminate key ports as invasion epicenters. These results emphasize the importance of implementing improved methods of ship-board treatment (through such methods as adding toxins to ballast water, filtration units on decks, U.V. radiation or centrifuges), and moving beyond the current practice of ballast water exchange in which ships pump out ballast water in the middle of the ocean.p. The Royal Society, founded in 1660, is the independent scientific academy of the United Kingdom and is dedicated to promoting excellence in science.

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