ND researchers study effects of ballast water
Andrew Thagard | Monday, February 23, 2004
In a study slated to debut in Britain next month, Notre Dame researchers John Drake and David Lodge analyzed the biological effects of ballast water from ships, identifying global hotspots and offering suggestions to combat the problem.The study will premiere in print form in the “Proceeding of the Royal Society,” a publication from a British scientific academy.As cargo ships distribute goods across the world, they take on and later dump thousands of tons of sea water – and microbes, small invertebrates and the eggs and larva of various marine species – in order to maintain balance and preserve the vessel’s structural integrity. Although the pumping process and hostile environment of the ships’ hulls kill the vast majority of these organisms, the sheer quantity of water cycling through each year worldwide – three to five billion tons, according to the Global Ballast Water Management Programme – means some will survive transport and disrupt the ecosystems where they are dumped.The introduction of European zebra mussels to the Great Lakes and an Asian species of kelp into the waterways of South Australia, for example, has displaced native species. The invasion of a type of North American jellyfish in the Black Sea has resulted in the collapse of some commercial fisheries in the region.Perhaps more frightening is the threat that invading microbes bring – causing cholera outbreaks and spreading red tide.”It’s a practical problem that needs to be solved,” said Drake, a Ph.D. candidate who worked with Lodge, a biology professor, on the project. “[This discharged water] is responsible for hundreds of nuisance species around the world. Ballast water is also a concern because it moves around human pathogens.”The researchers sifted through data from over 28,000 ship arrivals collected at 243 ports around the world. The information they gathered was used to construct a simulation of ship traffic that also relied on gravity models to assess water movement. Mathematical manipulation of the data allowed Drake and Lodge to estimate the rate of port to port invasions and determine which areas face the greatest danger.The results, Drake said, were surprising. While places like the Great Lakes and San Francisco Bay area often receive more attention, the true global hotspots for ballast water invasion are located in Asia and parts of Europe. Part of the reason for increased attention to certain areas, Drake said, is that wealthier countries like the United States have more resources to study the problem while their less affluent counterparts typically overlook it.”I think the correct interpretation is that more intensely sampled areas aren’t [necessarily] hot spots,” he said. “There’s a lot of bias on where the problems are being reported.”The study also looked at possible ways of dealing with the problem beyond today’s preferred method of dumping it into the open ocean – a solution that is not effective. All the eliminated water can endanger the ecosystems of islands located “down stream.”Drake’s and Lodge’s findings suggest eliminating the threat of biological invasions from ballast water at key ports by constructing processing plants to dispose of it would not significantly address the problem. The best solution, the researchers said, may be to install treatment methods aboard ships that kill the organisms using ultraviolet light or other means.”We found far and away that implementing the on-board technology is a better strategy,” Drake said.