By JEFF DONN
Associated Press Writer
Hordes of microorganisms, including viruses and other germs that may harm people or marine life, sail into U.S. ports from abroad every year in the ballast water that keeps ships stable, a study says.
It suggests that microorganisms may pose a greater danger than bigger, known invaders in ballast water, like mussels.
The research is likely to intensify the push for more restrictions on dumping ballast water near the shore.
``We need to broaden our focus and think of the smaller organisms that are clearly many orders of magnitude more abundant and can be potentially as potent and may be much more difficult to remove,'' said marine ecologist Gregory Ruiz, who led the study at the Smithsonian Environmental Research Center in Edgewater, Md.
The researchers, whose findings were published in Thursday's issue of the journal Nature, took samples of ballast water from 15 seagoing ships in Chesapeake Bay off Virginia and Maryland.
Seagoing ships carry ballast water â€” which is separate from unwanted bilge â€” to keep the boat floating right. When the cargo or the weather changes, ballast must sometimes be dumped.
Ships must release it 200 miles out to sea under state or federal regulations for the Great Lakes, California, Washington state and a few other places. For most ports, though, federal law makes the rule voluntary. About 87 million tons of foreign ballast water is discharged into U.S. ports each year, according to the study.
The researchers tested ballast water from ships that came mainly from Europe and the Mediterranean Sea. They calculated that each gallon of ballast water carried an average of 31 billion suspected viruses and 3.5 billion bacteria, including some disease-causing strains of cholera. Other microbes were not identified, but the researchers say they could well include some that harm local marine plants and animals or people.
Most researchers and policy-makers have concentrated on the dangers of invading mussels, clams, jellyfish and other visible threats in ballast water. Zebra mussels, native to the Black Sea, are clogging water intake pipes around the Great Lakes.
``We basically forget about the pathogens. Perhaps they are there and potentially as important as the other invasive species,'' said Christopher Brand, who studies animal diseases at the National Wildlife Health Center at Madison, Wis.
Specific microbial invaders in ballast water are suspected in just a few outbreaks. They can be serious, though. Two years ago, cholera-like bacteria infected Gulf Coast oysters and sickened hundreds of people who ate them around the country.
``I think there's a significant risk involved,'' said bacteriologist Jay Grimes, who studies germs in ballast water at the University of Southern Mississippi.
Reacting to the study, some researchers and conservationists endorsed stronger offshore dumping rules. Even with discharge far out at sea, though, some microorganisms linger, prompting calls for disinfection of the ballast water with ultrasound, filtration, heat or other technology.
Worried about a spreading patchwork of state rules, some industry groups have recently backed federally required offshore discharge for all U.S. ports. But they say the most economical and safest approach for the long term is to develop better methods to treat ballast.
``We think the solution for microorganisms is the same as for large animals: It's the technology for treating ballast in the vessels,'' said Tom Chase, spokesman for the American Association of Port Authorities.
Marine biologist Andy Cohen at the San Francisco Estuary Institute said ballast water could be piped to waste water treatment plants.
``There's no technological challenge or invention needed â€” just the will to go ahead and do this,'' he said.
On the Net: http://nas.er.usgs.gov/publications/ballast.htm, U.S. Geological Survey on invasive species in ballast water
http://www.aapa-ports.org/feature3.html, American Association of Port Authorities statement on ballast