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
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
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.
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
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.''