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Great Lakes Article:

Nitrogen gas could kill exotic species, protect ports

Mercury News
January 7, 2001

From San Francisco Bay to the Great Lakes, exotic species of plants and animals are invading America's waterways -- killing native species, clogging water pipes and disrupting the food chain -- often after hitching a ride in the ballast water of large foreign cargo ships.

Now a Monterey Bay scientist appears to have found a promising solution: Deprive the little stowaways of oxygen and save ships from rusting at the same time.

Working with Japanese researchers, Mario Tamburri, a research fellow at the Monterey Bay Aquarium Research Institute in Moss Landing, found that if shipping crews pump their ballast tanks with nitrogen gas while at sea, oxygen in the ballast water is virtually eliminated, reducing corrosion of a ship's steel compartments by 90 percent.

Sucking out the oxygen also kills fish, crabs, mussels, clams and other exotic species lurking in the ballast tanks within three days, Tamburri found.

``This is a win-win solution,'' Tamburri said. ``It actually saves the shipping industry money and kills most of the invasive organisms.''

Over the 25-year life of a large cargo ship, the process can save $1.7 million, or $70,000 a year, in painting and maintenance costs, even when the cost of the nitrogen system is factored in, Tamburri and his colleagues found. As an added benefit, most of the biological stowaways are eliminated.

The finding offers hope for one of the world's most vexing new environmental problems.

For the first time, companies that own large cargo ships, oil tankers and other vessels may have a financial incentive to kill exotic worms, crabs, fish, clams, plants and other species before the animals are flushed out with ballast water to disrupt rivers and bays in ports of call. Other methods, including using poisons, filters and ultraviolet light, are expensive and have not been used beyond the experimental stage.

Industry interested

The findings by Tamburri, Kerstin Wasson of the Elkhorn Slough National Estuarine Research Reserve in Moss Landing and researchers at Sumitomo Heavy Industries in Yokosuka, Japan, are published in the January edition of Biological Conservation, a scientific journal.

On Monday, the study was greeted favorably by environmentalists and the shipping industry.

``From first glance, this looks very promising,'' said John Berge, vice president of the Pacific Merchant Shipping Association, in San Francisco. ``The industry recognizes that it is a problem. We want to try and work on it. But there is a lot of uncertainty in terms of what is the best approach.''

Environmentalists have lobbied for new laws in recent years to force ships to discharge their ballast water in the open ocean. A national law is voluntary. California, Oregon and Washington have mandatory state laws requiring discharge 200 miles offshore, but there is little enforcement.

``Up to 1 billion gallons of foreign ballast water is discharged into San Francisco Bay every year,'' said Linda Sheehan, Pacific region director of the Ocean Conservancy, an environmental group in San Francisco. ``It is a major problem. It is the major source of aquatic invasive species. It really is important for us to start treating it.''

Because global shipping moves 80 percent of the world's trade, the problem of shifting unwanted species across the world has exploded out of control.


A large cargo ship that is 750 feet long might have a dozen or more ballast tanks below deck, each the size of a high-school gymnasium. The tanks hold millions of gallons of water.

Water is sucked in at one port and used to keep the ship low, submerging the rudder and allowing for greater stability. When the ship's cargo is transferred, its ballast water is released, dumping millions of foreign organisms into rivers and bays.

Exotic pests are estimated to cost U.S. taxpayers tens of billions of dollars a year.

There are at least 4,000 non-native plants and 2,300 non-native animals now established in the United States, according to the U.S. Fish and Wildlife Service. They thrive because they have few, if any, predators and often are impervious to local disease. They crowd out local species and gobble up food sources.

In San Francisco Bay, the Chinese mitten crab is burrowing into levees across the bay and its delta, increasing flood risks and clogging water intake pipes for the vital Central Valley Project near Tracy.

The hardy zebra mussel, which federal officials estimate will cost $5 billion to remove from the Great Lakes, has jammed water pipes and cooling systems at power plants across the Midwest, and has crowded out native clams and fish.

In San Francisco Bay or around its shores, there are at least 234 species of foreign plants, crabs, worms, fish, mammals and other animals, according to a 1998 study by biologist Andrew Cohen of the San Francisco Estuary Institute in Richmond.

Cohen said that removing oxygen from ballast water will kill most invertebrates and their larvae. He said that other methods still may be needed for marine algae, bacteria and other species.

``No single system will get everything, but this could be a great help,'' Cohen said. ``Invasive organisms are now having more impact to endangered species in America than pollution, hunting or fishing.''

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