Bathed in early morning light, the Caspian Prince, a 900-foot freighter leaves Antwerp, Belgium, bound for the Port of Wilmington, N.C., to fill its cargo hold with tobacco. For this leg of its journey, the ship is empty… or so it seems.

Within the Caspian Prince’s hold and ballast tanks are millions of gallons of seawater, drawn from the northern European harbor to lend stability and trim to the vessel during its two-week ocean crossing.

The ballast water contains a mini-menagerie of aquatic organisms — minute jellyfish, larval mussels and barnacles, marine worms, tiny shrimp-like copepods and juvenile fish. These creatures share their confines with an assortment of single-celled plants and even smaller bacteria and viruses. Many of these organisms can withstand the hardships of a journey across the Atlantic Ocean.

When the ship docks in Wilmington and empties its ballast tanks before loading its cargo, the plants, animals and microbes are unintentionally released into the Cape Fear River. Freed from their confines, the ballast water organisms may multiply and thrive.

This scenario may be imaginary — but the concern is real.

It is likely how the zebra mussel, a fingernail-sized mollusk from the Black, Caspian and Azov seas entered the Great Lakes in the late 1980s. Since their introduction, zebra mussels have spread rapidly to all of the Great Lakes and to waterways in many states, as well as the Canadian provinces of Ontario and Quebec. Growing in dense clumps, the mussels can encrust and foul facilities at power plants, fish ladders and industrial sites. To date, natural resource managers have been powerless to stop the mussels’ spread.

“Thousands of species of marine life are currently being transported in ballast water,” says William Cooper, a Sea Grant researcher at the University of North Carolina at Wilmington. “It’s unclear what long-term effects such large-scale introductions will have, but the evidence to date suggests there could be serious trouble ahead,” he adds.


Releases of ships’ ballast water have been blamed for the spread of the bacteria known to cause cholera. In the Chesapeake Bay, for example, researchers have identified a new strain of Vibrio cholerae, the organism that causes cholera, with origins in the Mediterranean or North seas. Health officials in Delaware, Maryland and Virginia must remain vigilant to prevent outbreaks of the disease caused by this particular strain.
Introductions of exotic plankton species can shift the balance of aquatic ecosystems. First sighted in Cape May County, N.J., in 1988, the non-indigenous Asian shore crab (Hemigrapsus sanguineus) has rapidly expanded its range. This small (1.5-inch) but highly adaptable crustacean now occupies coastal niches from Maine to North Carolina. Researchers anticipate that the crab will continue to proliferate, edging out native species that share its habitats.

The problem of unwanted ballast water organisms is hardly limited to the East Coast. In San Francisco Bay, for example, more than 230 non-native aquatic shore-dwelling species already have taken over in mudflats, shoals and along the coast.

On the lower Columbia River, a natural boundary between the states of Oregon and Washington, at least 61 of the 292 known plant and animal species are non-native. Some, such as the Asian clam (Corbicula flumine) so thoroughly dominate the sediment in some stretches of the Columbia that little else can survive. If that’s not bad enough, these introduced pests can proliferate to such a degree that, like zebra mussels, they will eventually clog irrigation ditches and fish screens.

With funding from a National Sea Grant initiative and other sources, Cooper and his West Coast counterpart, Russ Herwig, with the Washington Sea Grant Program in Seattle, are looking at ways to curb future introductions of ballast water organisms along the nation’s coasts.

For the past three years, Cooper has been working with a team of scientists to develop the technology to treat ballast water before it is dumped. For nearly two years, Herwig’s crew has been testing the new equipment in the field, working aboard the oil tanker S/T Tonsina. It is one of a fleet of tankers that carries oil — and ballast water — from the Port of Valdez in Southeast Alaska, to Long Beach, Calif., Puget Sound, Wash., and other destinations along the Pacific Ocean coast.

This collaborative project began several years ago, when the Tonsina‘s principal owner, British Petroleum, recruited Nutech O3, Inc. of MacLean, Va., to develop and design a shipboard ballast water treatment system, using ozone as the active ingredient. Nutech recruited Cooper to oversee the ozone chemistry at play.

In turn, Cooper contacted Herwig and his colleagues at the University of Washington, asking them to conduct field tests of the system. Cooper and Herwig saw the national and international importance of applied research on ballast water — and the Tonsina would provide a demonstration opportunity to evaluate how the ozone theories would translate to real shipboard experiences.


Ozone gas is produced when an electrical impulse is shot through air that is rich in oxygen.

“When you smell the air after a lightning storm, you’re smelling ozone,” Cooper explains. Ozone has been used for decades to disinfect drinking water, swimming pools and aquariums. It is incredibly effective at killing bacteria and viruses in water. Because it degrades quickly, reverting back to oxygen, it is safe for these freshwater applications.

Today, the Tonsina is equipped with almost seven kilometers of stainless steel tubing through which ozone gas is conveyed to the ship’s ballast water. The process is relatively simple, and there is no need to bring potentially harmful chemicals on board ship. “All you need is electricity and air,” Cooper notes.

A stream of oxygen-rich air is sent through an electrode, exposing the gas to 10,000 volts of electricity. The ozone gas that emerges is then sent to the 15 ballast tanks on board through a system of 1,200 diffusers, which Cooper compares to aerators in fish tanks. The gas bubbles through the ballast water continuously while the ship is in transit. Ozone oxidizes the tissues of any ballast water organisms inside, destroying them.

According to Cooper, the ideal ballast water treatment system would kill organisms of all sizes, a requirement that many potential technologies have failed to meet. “We’re looking at every trophic level in the water system, from viruses and bacteria all the way up to fish,” the UNC-W chemist says.

While ozone kills microorganisms like bacteria and viruses almost immediately, larger organisms often escape treatment. However, when ozone reacts with bromide naturally present in seawater, bromine is formed. Bromine extends the effects of ozone treatment because it also can disinfect — and bromine does not degrade as rapidly as ozone.

This combination of ozone and bromine has the potential to eliminate entire populations of microbes and planktonic organisms within the ballast water tanks. Initial tests, conducted in Long Beach, Calif., and Port Angeles, Wash., have shown that the ozone treatments can kill up to 99.99 percent of the bacteria and phyto-plankton in ballast water.

The system was somewhat less effective at destroying zooplankton, but the success rate was still above 90 percent.


As one group of scientists monitors the effectiveness of the Tonsina‘s ozone treatment technology, another gathers samples of ballast water organisms. This means gaining access to each ballast tank through a service hatch, or manway — an access secured with many bolts, some rusted in place since last time the ship was serviced. “The ship’s crew has been extremely cooperative and very interested in watching our sampling efforts,” Herwig says.

Once the crusty hatches are cracked open, the team collects plankton samples, pulling a small plankton net, or “tow,” through the tank. One tow will amass about 5,000 planktonic organisms in its stocking-shaped sieve. Microbe-laden water samples also were collected in five-liter Niskin bottles for subsequent lab analysis.

“Collecting samples is the fun part,” Herwig says with a wry grin. “After that comes many hours spent processing samples and sorting those tiny planktonic organisms by genus and species.”

While sorting the plankton, the researchers seek to distinguish foreign species from those native to North America’s West Coast waters. They also try to recognize species associated with coastal and open ocean habitats.

That latter distinction is especially valuable in gauging the effectiveness of what scientists call mid-oceanic exchange — an international voluntary ballast water management measure.

To reduce the possibility of introducing exotic aquatic organisms, the Washington State Legislature recently approved a bill requiring transoceanic vessels to empty and refill their ballast tanks in the open ocean. Vessels entering U.S. ports are required to report these activities to the U.S. Coast Guard.

Legislatures in California, Hawaii, Maryland, Oregon and Virginia have enacted similar laws. Though not legislated in North Carolina, Erik Stromberg, North Carolina Ports Authority executive director, spearheaded efforts in 1998 to ensure that vessels en route to state ports engage in ballast water exchange before entering the U.S. Exclusive Economic Zone.

Ballast water exchange on the high seas greatly reduces the chances of ships ferrying planktonic aquatic organisms from one nearshore area to another.
Alas, seawater swapping is probably not sufficient to eliminate the threats from ballast water releases. The designs of most ballast tanks make it difficult to drain every drop of water or replace all of the living organisms in a ballast tank, says Herwig. Sediments also may accumulate in the nooks and crannies of a ballast tank. Living organisms and resting stages of organisms may accumulate in the sediments.

Furthermore, Washington’s ballast water regulation has a loophole. A ship’s crew can be exempted from making mid-ocean exchanges if stormy seas or other conditions would present insurmountable safety hazards.


Ozone treatment may sound great in principle, but there’s still work to be done. That’s because the extended life of bromine can raise environmental concern. Ozone’s quick decay rate means it is unlikely to threaten native life when the ballast water is poured out.

Longer-lived bromine, however, still may be present in the released water, so scientists must make sure that bromine will not harm the aquatic systems into which it is released. For this reason, researchers are trying to pin down the lowest concentration of ozone that will get the job done.

Lower concentrations of ozone also will reduce operational costs — an important consideration in getting the shipping industry to adopt this technology. The Tonsina‘s formidable network of stainless steel pipes almost certainly would be too expensive for most ships to install, so the experimenters also are exploring a less costly alternative system.

Instead of bubbling ozone gas through a maze of tubes for the entire voyage, the new streamlined set-up simply will inject ozone into the seawater on its way to the ship’s ballast tanks.

Herwig suspects that employing a combination of ballast water treatment technologies — ozone, ultra-violet light, chemical additives and fine-meshed filters — ultimately may be the best way to tackle the invasive species problem. Perhaps different technologies will be appropriate for different types of vessels, he suggests. There also may be sequential treatments developed.

Many researchers, says Herwig, believe that a filtration step could be used first to remove larger organisms and then a second step, perhaps ozone treatment, would follow to remove the smaller life. For now, though, there is no consensus about which methods are most likely to pay off.

One thing is certain, however: industry approval is key. “Wherever our research takes us, it’s essential that we work closely with the shipping industry,” Herwig notes. “There’s no point in coming up with measures that are too impractical to be implemented. What shipping company would be eager to adopt a technology that took up three-fourths of a cargo hold? Understanding and solving the problems associated with ballast water also requires a multidisciplinary approach, teams of scientists, engineers and representatives from the shipping and regulatory communities.”

Cooper agrees with Herwig’s assessment. “The industrial component of this is very large and very cooperative,” he says. “This particular project is an example of multi-institution academic and private industry cooperation and collaboration, which has led to some astounding results that we would not have been able to obtain if this cooperation wasn’t in place.”

Collaborators on this project currently include Gregory Ruiz from the Smithsonian Environmental Research Center, Robert Gensemer from Parametrix, Inc., Paul Dinnel from Western Washington University, and Jeffery Cordell from the University of Washington.

Industry partners come from BP Oil Shipping Company, the Alaska Tanker Company, Nutech O3, Inc., and Northeast Technical Services Company, Inc. of Olmstead Falls, Ohio.

Each Thursday, a conference call connects scientists and executives from all of the participating institutions. “No one is left out,” Cooper says. “Everybody has an equal say. We all decide where we’re going and how we’re going to get there most efficiently, and then we charge off.”

Cooper also emphasizes that, though cost is of course a consideration, the group holds its work to high scientific standards.

“The most important thing is that we do research that’s scientifically defensible. That’s been the philosophy of our collective group ever since we started,” he says.

“We’re doing it because we want to get answers to solve real problems.”

David G. Gordon is a science writer with Washington Sea Grant, where Melissa Lee Phillips is a communications intern.


In 1990, Congress directed the U.S. Coast Guard, then under the Department of Transportation, to establish a mandatory national ballast water management program for vessels entering the Great Lakes.

Then, in 1996, Congress directed the Coast Guard to establish a national ballast water management program that included a voluntary mid-ocean exchange initiative for transoceanic vessels — with mandatory reporting. However, compliance is sketchy at best.

When the Coast Guard was transferred to the Department of Homeland Security in 2003, ballast water management became a priority.

At the urging of both the Coast Guard and the American Association of Ports Authorities, the department published a “Notice of Proposed Rulemaking” in the National Register: “The Coast Guard proposes mandatory ballast water management practices for all vessels equipped with ballast tanks bound for ports or places within the U.S. and/or entering U.S. Waters. The Great Lakes (mandatory) ballast water management program would remain unchanged. The proposed rulemaking would increase the Coast Guard’s ability to protect U.S. waters against the introduction of NIS (nonindigenous species) via ballast water discharges.”

Currently the Department of Homeland Security is reviewing comments and is expected to develop the final rule in 2004.

Along with mid-ocean ballast water exchange and reporting, the rules would approve alternative “environmentally sound” methods of ballast water management as they are developed and tested for effectiveness.

In addition, the International Maritime Organization currently is negotiating a binding international agreement for mandatory ballast water management by member nations. Adoption is expected in 2004, with ratification and implementation by 2006.

For a complete overview of the ballast water issue, here are a few resources:

This article was published in the Holiday 2003 issue of Coastwatch.

For contact information and reprint requests, visit