Great Lakes and St. Lawrence Seaway
Connecting the Atlantic Ocean and the Great Lakes, the St. Lawrence Seaway opened in 1959.

On January 1, Michigan became the first state in the nation to regulate ballast water that is pumped into and out of tanks in ocean-going vessels for stability. The new regulations are intended to prevent the introduction of non-native species into the Great Lakes. Opinions vary about the utility of Michigan’s regulatory approach, but there’s broad agreement that more research is needed to improve ballast water treatment methods.

Ballast water is used to fill the hulls of ships that have been emptied of cargo and thus require weight for safe passage. In the days of wooden ships, sailors used rocks, sand, wood and other substrata from shore as dry ballast. Modern steel-hulled ships are better suited to ballast water, which can be pumped in greater volumes more quickly.

Ballast water is uploaded or discharged depending on the weight and placement of cargo. One freighter alone can carry tens of millions of gallons of ballast water — and thousands of species therein. When ballast is discharged at a destination harbor, foreign organisms are introduced into the local waters. The speed and reach of modern vessels allows a greater variety of species to survive transatlantic journeys to many more non-native shores. This phenomenon is not unique to the Great Lakes, nor is it of recent origin; from both dry and wet ballast, it has occurred for centuries along virtually all coastal waters.

The opening of the St. Lawrence Seaway to the Great Lakes in 1959 accelerated the introduction of non-native species into the basin. The number of such species is estimated at upwards of 180, with some having arrived in the 1800s. The majority of non-native species in the Great Lakes — some 70 percent — are believed to have originated from the Ponto-Caspian region (which includes the Black, Caspian and Azov seas).[1]

Invasive species proliferate in non-native waters due to the absence of natural predators and diseases that would otherwise constrain them. Their effect on the indigenous ecosystem may be profound and, in some instances, beneficial. Given the changes in ecosystems across the millennia and the near-infinite pathways of species relocation, the classification of native vs. non-native species is not exact.

In hopes of stemming yet more introductions, the Michigan Legislature in 2005 directed the state Department of Environmental Quality to craft a permit regime for all ocean-faring vessels operating at Michigan ports as of Jan. 1, 2007. To obtain a permit, applicants must prove that the vessel will not discharge any ballast water that has not been treated to prevent the introduction of exotic species into the Great Lakes. Four specific treatments are permitted: the use of chlorine dioxide and hypochlorite, both chlorine-based disinfectants; ultraviolet light radiation, which deactivates viruses and bacteria; and, deoxygenation, which displaces oxygen in water.[2]

Relatively simple as the permit requirements may seem, the effective treatment of ballast water is exceedingly complex. There does not exist at present any single treatment capable of eliminating the variety of species that exist — even thrive — in ballast water and the sediment that collects in ballast tanks.

The complexity stems, in part, from the variation in vessels. Crude tankers, bulk carriers, container ships, cruise ships and pontoons, to name a few, all possess ballast tanks of varying volume, and geometry and pumping configurations, which together defy a uniform technology or process.[3] Devising an effective treatment also must account for myriad operational challenges such as:

  • The safety of crew members and passengers with toxic chemicals onboard.

  • The disposal of toxic chemicals used in treatment. (Biocides and pesticides are tightly regulated by the U.S. Environmental Protection Agency.)

  • Older vessels with limited capacity for retrofitting.

  • Interference with ship operations. (Treatment requires additional power, crew and space.)

  • Disruption of trade schedules and routes (for retrofitting).

  • The effects on treatments and equipment from the vibration, pitching and rolling that are unavoidable during ocean voyages.

Exacerbating matters is the astonishing array of organisms present in ballast water, including zooplankton, phytoplankton, bacteria and viruses, all of which respond differently to treatment depending on life cycles, water quality and a host of other factors.

Summarizing the challenge, the research team of Glosten-Herbert LLC and Hyde Marine concluded: "A single technique has not yet been found that can handle all of the target organisms with reasonable dosages or equipment parameters. The biodiversity is just too great (in terms of size and sensitivities). Differences in the size of ships and the quantities of ballast water handled add to the complexity of the ideal solution. Finally, a ship’s trade route may alter the primary target organisms when a risk-based approach to control of species is introduced or regional standards are encountered."[4]

Federal law currently requires ocean-going ships destined for the Great Lakes to exchange ballast water with salt water at least 200 miles before entering the St. Lawrence Seaway. Organisms from coastal waters are unlikely to survive in the open ocean. However, ballast water exchange is never 100-percent complete. Even ships loaded with cargo and without "pumpable" ballast water may still transport non-native species into the lakes through tank sediment.

The U.S. Coast Guard is currently developing national standards for the discharge of ballast water. Similarly, the United Nations’ International Maritime Organization is seeking ratification among its 30 member states of a ballast treatment "convention."

Benefits and Drawbacks of Ballast Treatment Alternatives

Treatment Type





Sound waves destroy organisms.

No chemical byproducts. Effective against microorganisms.

Ineffective against larger organisms. Undeveloped for large volume ballast. Expensive.


Chemicals such as chlorine, bromine or iodine added to ballast water destroy organisms.

Can be effective on all organisms at varying concentrations. Easily stored.

Chemicals can corrode tanks, pipes and pumps. Potential for environmental contamination and toxic exposure to crew. Expensive. Lack of research on interaction between biocides and sea water.

Closed ballast system

Purification of ballast water at ports.

Containment of organisms and toxic chemicals.

Impractical logistics. Costly to retrofit.


Inert gases or bacteria displace oxygen in ballast water.

Non-toxic. Prevents hull corrosion. Effective on fresh water and salt water.

Expensive. Requires specialized crew and equipment. Potentially ineffective on some species in cyst stages and anaerobic bacteria.

Electric Pulses

Bursts of energy electrocute organisms.

Potentially effective.

Experimental. High power requirements. Specialized crew.


Filters prevent organisms from entering/exiting ballast tanks.

Speedy. Can retain organisms in natural habitat. No chemical byproducts. Removes suspended solids. Readily available.

Expensive. Not effective against bacteria and viruses. Potential for clogging and slowing flow rate.


Use of engine cooling system to raise temperature of ballast water.

No chemical byproducts. Effective with large organisms such as fish.

Less effective against microorganisms. Limited by engine size. Potential for tank corrosion. Dangerous for use on chemical tankers.


Centrifugal force separates organisms from water.

Effective removal of species heavier than saltwater. Available technology.

Ineffective against microorganisms. Storage and removal of captured organisms.


Sequential processes involving introduction of ionized gas; air is then passed through ultraviolet and magnetic fields to create oxygen and nitrogen ions; ions are injected into water, causing organisms to coagulate for removal.

No known environmental impacts. Safe for crew.

Experimental. Large footprint and complex instrumentation requiring specialized crew.


Ozone gas reacts with chemicals in sea water to destroy organisms.

Particularly effective against microorganisms.

Space requirements for generators. Corrosive. May require neutralization before discharge.

Whether the treatment methods prescribed by Michigan regulators will prove effective is a matter of debate. According to Curtis Hertel, executive director of the Detroit/Wayne County Port Authority, "The treatment methods endorsed by MDEQ have not yet been proven to be effective."[5]

In deciding on treatments for permitting, the DEQ reviewed a variety of studies that measured the effectiveness against specific "indicator" organisms. Critics contend, however, that the agency failed to review studies that measured the type and number of organisms overall that remained in the ballast water following treatment — the type of measurement called for by the International Maritime Organization.

Moreover, the Michigan Environmental Science Board, in reviewing the results of a ballast treatment demonstration project involving one of the DEQ’s treatment options, warned that the conclusions regarding the effectiveness of sodium hypochlorite "can only be considered preliminary at best.[6]

"Considerable more work will need to be conducted before any definitive statement regarding its efficacy within an actual ballast water tank environment can be made. … Insufficient information (too few tests and lack of data as to what requirements would need to be met throughout the Great Lakes jurisdictions) was provided to definitively address the question regarding if such discharges could be safely and legally discharged into Great Lakes waters."

Jurisdictional challenges also exist. There are 15 major international ports and some 50 smaller, regional ports on the Great Lakes-St. Lawrence Seaway.[7] The Michigan regulations apply only to ports within the state, and thus will not affect releases of ballast water elsewhere in the basin.

[1] Gracki, J.A., R.A. Everett, H. Hack, P.F. Landrum, D.T. Long, B.J. Premo, S.C. Raaymakers, G.A. Stapleton and K.G. Harrison. 2002. Critical Review of a Ballast Water Biocides Treatment Demonstration Project Using Copper and Sodium Hypochlorite, September 2002. Michigan Environmental Science Board, Lansing.

[2] Michigan Department of Environmental Quality, Ballast Water Control General Permit.

[3] Glosten-Herbert LLC and Hyde Marine, "Full-Scale Design Studies of Ballast Water Treatment Systems," April 2002.

[4] Glosten-Herbert LLC and Hyde Marine, "Full-Scale Design Studies of Ballast Water Treatment Systems," April 2002.

[5] Letter from Curtis Hertel, executive director of the Detroit/Wayne County Port Authority, to William Creal, Chief of Permits Section, Water Bureau, Michigan Department of Environmental Quality, March 10, 2006.

[6] Gracki, J.A., R.A. Everett, H. Hack, P.F. Landrum, D.T. Long, B.J. Premo, S.C. Raaymakers, G.A. Stapleton and K.G. Harrison. 2002. Critical Review of a Ballast Water Biocides Treatment Demonstration Project Using Copper and Sodium Hypochlorite, September 2002. Michigan Environmental Science Board, Lansing.

[7] Great Lakes Information Network.