World Ocean Observer - Exporting Pollution

Exporting Pollution

Tundi Agardy, Ph.D.

Ships have changed the world. Consider the role that sea-going vessels
have had in rise of some of the greatest civilizations: those of
ancient India and China, the Vikings, or the Mediterranean-based
Phoenicians, Greeks, and Romans. Maritime traffic has allowed cultural,
biological, and commercial exchange, profoundly influencing the
development of both individual societies and the world as a whole1.


Photo Credit: Craig Dickson, WHOI

And maritime military might has allowed nation states to increase and retain their power, perhaps more than any other kinds of technology. This is as true today as it was centuries ago.

Yet ships and shipping have changed the world in less obvious ways as well. For all the benefits maritime vessels have provided societies, these have come at a largely hidden environmental cost. Through merchant marine and naval shipping activities, countries have both deliberately and inadvertently exported pollution, affecting marine species and in some cases changing the very nature of entire marine ecosystems.

That the oceans are a repository for all sorts of human-derived wastes is something most people know something about, given the striking images in the media of debris-laden waterways, syringes washing ashore on beaches, and plastic entangling seals, turtles, and birds. But exporting pollution occurs in more subtle, and infinitely more damaging, ways. Here we focus on three ways that pollution is exported, whether deliberately or inadvertently, and the consequences of such pollution for marine ecosystems worldwide. These phenomena include ship disposal at sea, the spreading of alien species, and the proliferation of underwater noise pollution.

Ship Decommissioning, Ship-Breaking, and Ship Disposal

Shipping is big business, financially, of course, but also in terms of the sheer numbers of ships out on the sea. The number of ocean-going vessels, ranging in size from pleasure boats to aircraft carriers, is staggering. The Lloyds registry alone has 200,000 entries for merchant ships larger than 100 gross tons, and this number is dwarfed if one adds military, fishing, and private vessels to the mix. In 2005, the total number of merchant ships of at least 1,000 gross tons was 30,936 2. This number does not include military vessels (for which information is difficult to compile), research vessels, ships used in oil and gas exploration, or commercial fishing vessels, all of which can be extremely large and probably number in the tens, if not hundreds, of thousands collectively.


Bissau Harbor, Guinea Bissau (Credit: T. Agardy)

These ships do not last forever, of course, and when they are no longer useful, their disposal creates major challenges. The issue of what to do with decommissioned or unusable vessels has clearly grown since the days of the Phoenicians or Greeks, or even the great era of oceanic exploration during the 15th through 19th centuries, when vessels were constructed of natural, biodegradable materials.

Today, ships are floating hazardous waste sites, containing heavy metals, persistent organic pollutants, non-biodegradable plastics, hydrocarbons, and even nuclear materials. And although the London Dumping Convention stipulates that vessel disposal on the high seas is prohibited3, countries continually dispose of ships at sea within their waters, or export their hazardous waste-laden decommissioned ships to other countries, which are eager to get paid fees and largely ignorant of the consequences.

The struggles between maritime nations having to dispose of aging ships and developing countries who are willing to scrap them continue to this day. But these conflicts are cropping up between developed countries as well, as the public and special interest groups take note of the hazards of accepting such hazardous waste for disposal. Just last May (2007), the Basel Action Network and the Sierra Club, represented by EarthJustice, sued the U.S. Environmental Protection Agency and the U.S. Maritime Administration (MARAD) to prevent resumption of U.S. exports of contaminated naval vessels to foreign countries. This lawsuit means that the Bush Administration's plans to export nine "Ghost Fleet" decommissioned naval vessels was put on hold. The vessels contain tons of materials contaminated with carcinogenic and toxic substances such as PCBs, asbestos, mercury, and used fuel.


Cabo Verde tanker hulk (Credit: T. Agardy)

The decision was hailed as a victory by environmental groups as well as American labor organizations. Martin Wagner of Earthjustice stated the following in response to the ruling: "The management of U.S. toxic waste is a U.S. responsibility. Why dump our trash in other countries when we can take care of it here and create new jobs at the same time?"4


Currently there are 238 old ships in the United States National Defense Reserve Fleet, most located in Texas, Virginia and California, that will need to be dismantled. According to the Environmental News Service, some of the ships are in dangerous condition and pose an environmental threat as they have never been emptied of fuels, oils and other hazardous substances5.


Credit: Greenpeace, Tom Clements 2003, ID 58327

Ships containing nuclear material create special cause for concern. Nuclear submarines are generally cleared of their nuclear material when they are decommissioned in the U.S., but Russian nuclear submarines are not handled in the same way. Often, Russian nuclear submarines are left to rust before nuclear material is fully captured from the disposed vessels, primarily because facilities to remove and contain nuclear material are overburdened. As the graph below shows, significant numbers of Russian nuclear submarines are in existence today, and will have to be dealt with in the future.


Nuclear powered military ship construction in USSR (Russia) and USA 6

We would be remiss to discuss ship disposal without bringing up the issue of artificial reefs. Many smaller vessels are deliberately sunk at sea in order to create artificial reefs, which draw in fish from surrounding areas and create opportunities for both recreational and commercial fishing. However, the extent to which such artificial reefs actually boost fisheries production has been disputed - even though many ship disposals of this nature are "sold" to local decision makers as a biomass-enhancing tool. While there are certainly examples of well-cleaned decommissioned ships creating enhanced underwater habitats for marine organisms, the condition of the decommissioned ships must be thoroughly evaluated before sinking. Unfortunately, strict standards do not apply in many countries, and once the ship is sunk it is out of sight, out of mind - while slowly leaching poisons in the darkened depths.


Credit: T. Agardy

Ballast Water and Alien Species

A less direct but perhaps even more insidious export of waste occurs when ships pump their ballast water in the ports where they take on cargo. Ballast water is carried in ships to add weight and thus stability to cargo vessels and other large ships when they are not carrying loads in their holds. When such vessels reach destinations where they take on cargo or supplies, the ballast water is conveniently pumped out at sea and forgotten. In and of itself ballast water is largely innocuous - besides rust residue or a small amount of fuel, the water itself is not the problem. But when ballast water is pumped into a vessel at a port of origin, many eggs, larvae, and adult plants and animals go with it. When these organisms are pumped out at ports far away, they often find themselves in places without natural predators, and can outcompete local flora and fauna to wreak ecological havoc.

The stories of invasive marine species being transported and then released under shipping operations are fascinating and bizarre. Witness the saga of the zebra mussel, which invaded the U.S. Great Lakes and major rivers as a result of being borne in ballast water from the Black Sea region. The well-documented costs of the zebra mussel invasion borders on ecologic and economic disaster. In return for that favor, subsequent ballast water originating in the western Atlantic inadvertently brought the dreaded Mnemiopsis leidyi ctenophore to the Black Sea, where the jelly-bodied creature devoured the young of most commercially important fish species and caused the ecosystem to crash. This introduction occurred through ship ballast water sometime in the 1980s, and the voracious predator eagerly preyed on the struggling biota, causing the loss of over two dozen major fisheries in a short span of years7. Recently, the anoxic layer of this basin has expanded and moved upwards, making restoration of the sea to its once vibrant state difficult.

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Dreissena polymorpha Mnemiopsis leidyi

Ballast-borne alien species invasions have thus reshuffled many more of the world's marine ecosystems, and caused amazing ecological and economic damage in some places8.

Thanks in large part to port development, estuarine systems are among the most invaded ecosystems in the world, with exotic introduced species causing major ecological changes9. Often introduced organisms change the structure of coastal habitat by physically displacing native vegetation10. For example, San Francisco Bay (US), has over 210 invasive species, with one new species established every 14 weeks between 1961 and 199511. Most of these bioinvaders were borne by ballast water of large ships or occur as a result of fishing activities. The ecological consequences of the invasions include habitat loss and alteration, altered water flow and food webs, the creation of novel and unnatural habitats subsequently colonized by other exotic species, abnormally effective filtration of the water column, hybridization with native species, highly destructive predators, and introductions of pathogens and disease12.

Port development also sets the stage for alien species invasions, not through operation of the port itself but rather by port construction. Altering soft bottom habitat to hard bottom in the process often creates new assemblages of species, and facilitates range expansions of invasive species13. The resulting ecosystems may have losses in some ecosystem services, such as biodiversity. In New Zealand invasive species have displaced commercially important mussel beds, resulting in significant economic losses for many mussel farmers.

There have been attempts to control this problem, or at least dampen the effects of releases of competitively superior non-native species into coastal waters. New international agreements on the pumping of ballast water in commercial vessels have required ships to move at least 200 nautical miles away from land when discarding ballast water and its hitchhiking invaders - offshore, chances are less that the invasive species will gain a foothold14. Individual countries have also adopted ballast water regulations: Canada, for instance, has a ballast water management act to attempt to mitigate the problem15. In the U.S., the Coast Guard has established regulations and guidelines in order to comply with the National Invasive Species Act of 1996; however, the Environmental Protection Agency issued a regulation exempting ballast water discharges from the Clean Water Act. Legal findings in 2005 and 2006 found that such an exemption was plainly contrary to congressional intent, and the courts have ordered EPA to take specific action by September 2008 to ensure that shipping companies comply with the Clean Water Act and restrict the discharge of invasive species in ballast water 16.

Nonetheless, the spread of alien and invasive species continues almost unabated, as the number of ships on the sea continues to rise. And we now know that once alien species are released and take hold on ecological communities, trying to control their spread is an exceedingly costly, and mostly futile, exercise.


Credit: Maersk Sealand

Noise Pollution

We rarely think of noise as a form of pollution. But for hearing-sensitive marine creatures, whose sole source of communication over large distance is sound, the noise created by underwater explosions, ship engines, and military sonar can be devastating. Consider the sperm whale - a largely solitary animal that must find its mate by communicating low frequency sounds at depths. (At some "channels" in the deeper ocean, these signals can travel across entire ocean basins.) When anthropogenic noise clogs this channel, the whales cannot find one another to socialize and breed. Other cetaceans use sound to locate prey, and ship noise can prevent them from doing so. Such animals are so sensitive to noise that the cacophony of white noise that now exists in many parts of the ocean has deprived them of sleep and caused what appears to be psychological stress. And even many fish species that communicate with sound are suffering from an increasingly noise-polluted ocean.


Spinner Dolphins (NOAA)

Because noise is increasingly widespread and intense in ocean waters, much scientific attention has focused on it, but only very recently. In a chapter of a book on cetaceans in crisis, John Hildebrand writes about the impacts of anthropogenic sound on marine mammals: "...mounting evidence suggests that high intensity anthropogenic sound from sonar and airguns leads to subsequent strandings and mortality of beaked whales...A more pervasive, yet subtle, problem may be the effects of increases in background noise levels from commercial shipping."17

Most sources of anthropogenic noise occur in continental shelf areas that are the most important habitats for marine mammals and coastal fishes. The U.S. National Research Council has stated that for 119 species of marine mammals and for many non-mammalian marine species as well, hearing and echolocation is the single most important sense for foraging, communicating, and navigating18. The sound environment is an important aspect of marine mammal habitat, and yet it has only recently been the focus of research determining the ecological requirements of these highly valued, and in many cases, highly threatened species.

Anthropogenic noise may be subdivided into two sorts of threats: acute noise that can cause mortality, hearing impairment, or other sorts of physiological stress; and chronic lower level noise which can also cause physiological stress but can do further damage by interfering with sound-based navigation, communication, and foraging. Noise travels very efficiently in water - nearly 5X the speed of sound traveling in air19. Sound waves bouncing off the sea surface or sea bottom cause sound to reverberate, adding to the increasing levels of white or background noise in the oceans.


Sound at the seafloor; Credit:


Sound propagation; Credit:

Acute noise has been shown to cause mortality and acute morbidity in many different species of marine animals. Sources of acute noise include active military sonars, underwater explosions such was those occurring in dynamite fishing, ship shock trials, or underwater construction, and air gun array blasts used in seismic surveys. Such airgun arrays are towed behind the approximately 90 seismic vessels in operation today (20% of which are operating at any given time in the ocean), and they can fire every 10 seconds for days at a time. A low-frequency seismic array can generate 215 decibels of sound, comparable to a twin-engine fighter jet at takeoff. Necropsies on toothed whales that mass stranded after being in the vicinity of sonar-using military vessels and seismic vessels have shown ruptured earbones, hemorrhages in fatty tissues of the head, and air bubbles in the lungs and brain20. These animals have particularly acute hearing, and all sound-sensitive organs are affected by acute noise, especially those occurring at mid-frequencies (as is the case with the most damaging military active sonars).


Credit: U.S. Navy

Military active sonar emits loud sound waves that sweep across the ocean to reveal enemy submarines and other objects of security interest. Some mid-frequency sonar systems can emit 235 decibels, sound as loud as a rocket at launch. Even 100 miles from a low frequency sonar system, sound levels can approach 160 decibels, well beyond the Navy's own safety limits for humans21. And with a concerted move to perform more military exercises in the shallow waters that are home to many marine mammals, concern for the animals' welfare is growing.


It should perhaps come as no surprise that all the mass strandings of beaked toothed whales such as beaked whales, dolphins, and pilot whales that have ever been recorded have coincided with large scale naval exercises in the vicinity, including mass strandings in the Canary Islands (Spain), Bahamas, Ionian Sea (Mediterranean) and the southeast Atlantic coast of the United States.

Chronic sounds seem to generate less media attention but can cause enormous problems for animals that use sound to travel, feed and communicate. Ambient or chronic sounds are primarily created by the enormous numbers of vessels now plying the seas, by offshore wind farms, and by the long term operation of seismic airgun arrays. Such sounds are generally low frequency (but they can be of high intensity) and are prolonged; the most affected species seem to be baleen whales such as fin whales, sei whales, minke whales, and humpback whales. Many of us are familiar with the hauntingly beautiful and complex songs sung by humpback and other whales; less well known (and less admired!) are the sound communications made by coral reef fishes. These communications can be drowned out by the white noise generated by human activity.

But how such anthropogenic noise actually kills, maims or impairs marine animals is not clear22. A U.S. National Research Council report issued in 2005 entitled, " Marine Mammal Populations and Ocean Noise: Determining When Noise Causes Ecologically Significant Effects" presents a conceptual framework for understanding how noise can cause biologically significant effects like slowing growth, reducing survival, or lowering reproductive rates. In response to this call for research, and that offered by the U.S. Commission on Ocean Policy report, the National Oceanic and Atmospheric Administration of the U.S. is now proposing to expose marine mammals to loud sonar sounds and monitor their behavior. NOAA Fisheries' Office of Science and Technology has applied for a scientific research permit under the U.S. Marine Mammal Protection Act of 1972 and with Bahamian authorities to conduct these behavioral response studies with an international team of co-investigators23.


Photo credit:

In addition to undertaking more targeted research, there are some concrete steps being taken to try and tackle this large, amorphous, and difficult to address threat. A meeting of marine mammologists and conservationists sponsored by Dokumente des Meeres was held in the Canary Islands in June 2007 to explore the notion of establishing noise-buffered marine protected areas for beaked whales and other noise-sensitive species. The Canary Islands already has a moratorium on military sonar in its territorial waters - the result of a series of mass strandings that coincided with military exercises in the area. In the Alboran Sea off Spain's Mediterranean coast, the International Maritime Organization has agreed to move shipping lanes in order to protect resident Alboran dolphins24. And in the U.S., shipping traffic within the Stellwagen Bank National Marine Sanctuary has been rerouted to areas within the Sanctuary less frequented by whales. But much more needs to be done.

According to the Millennium Ecosystem Assessment25, toxics loading (in part caused by ship disposal), alien species invasions and noise will all further stress already degraded coastal ecosystems and may impede natural recovery and managed restoration. Human health and well-being will suffer as a consequence, unless the ‘exporting pollution' problem is addressed and dramatic improvements to coastal management are systematically made across wide regions of the globe.



1 J. H. Bentley. 1999 Sea and Ocean Basins as Frameworks of Historical Analysis The Geographical Review, Vol. 89, abstract accessed on on June 12, 2007

2 Central Intelligence Agency World Factbook

3 The London Dumping Convention of 1972 will eventually be superceded by the 1996 Protocol to the London Convention on the Prevention of Marine Pollution by Dumping of Waste and Other Matter when it comes into force. Twenty six ratifications are need to have the protocol enter into force; 20 countries have ratified it to date. See


5 Ibid.

6 Miasnikov E., Military Nuclear Powered Ships, In Nuclear Encyclopedia, ed. by A. Yaroshinskaya, Yaroshinskaya Charitable Fund, 1996, pp. 148-159 cited in Anatoli S. Diakov1, Vadim K. Korobov2 and Eugene V. Miasnikov. 1997. Nuclear Powered Submarine Inactivation and Disposal in the U.S. and Russia: A Comparative Analysis
Problems of Material Science, Issue 2 (8), 1997, pp.37-44).

7 Zaitsev, Y. and V. Mamaev. 1997. Biological Diversity in the Black Sea. A Study of Change and Decline. United Nations Publications, New York, NY (USA), 208 pp

8 This statement and the bulk of the two paragraphs that follow it are from Millennium Ecosystem Assessment. 2005. Vol 1 Current state and trends. Coastal Systems. Pp513-549 In Ecosystems and Human Well-Bring. Island Press, Washington, DC

9 Carlton, J.T., 1989: Man's role in changing the face of the oceans: biological invasions and implications for conservation of near-shore marine environments. Conservation Biology, 3, 265-273.
Carlton, J.T., 1996: Marine Bioinvasions: The alteration of marine ecosystems by nonindigenous species. Oceanography, 9(1), 36-43.

10 Grosholz, E., 2002: Ecological and evolutionary consequences of coastal invasions. Trends in Ecology & Evolution, 17(1), 22-27.
Harris, L.G. and M.C. Tyrrell, 2001: Changing community states in the Gulf of Maine: synergism between invaders, oversfishing and climate change. Biological Invasions, 3, 9-21
Murray, S.N., J.A. Zertuche-Gonzalez, and L. Fernandez, in review: Invasive seaweeds: Status of knowledge and economic policy considerations for the Pacific Coast of North America. Center for Environmental Cooperation, Montreal (Canada)

11 Cohen, A.N. and J.T. Carlton, 1998: Accelerating invasion rate in a highly invaded estuary. Science, 279(5350), 555-558

12 Bax, N., A. Williamson, M. Aguero, E. Gonzalez, and W. Geeves, 2003: Marine invasive alien species: a threat to global biodiversity. Marine Policy, 27(4), 313-323.
Ruiz, G.M., J.T. Carlton, E.D. Grosholz, and A.H. Hines, 1997: Global invasions of marine and estuarine habitats by non-indigenous species: Mechanisms, extent, and consequences. American Zoologist, 37(6), 621-632.

13 Ruiz, G.M. and J.A. Crooks, 2001: Biological invasions of marine ecosystems: patterns, effects, and management. In: Waters in Peril, L. Bendell-Yound and P. Gallagher (eds.), Kluwer Academic Publications, Dordrecht (Netherlands), 1-17.

14 The International Maritime Organization's agreement on Ballast Water Management has 10 contracting parties as of May 31, 2007; 30 are needed to have the treaty enter into force. See

15 See

16 See

17 Hildebrand, J. 2007. Impacts of anthropogenic sound. Pp100-123 In Conservation Beyond Crisis J.E.Reynolds III, W.F. Perrin, R.R. Reeves, S. Montgomery and T.J. Ragen (eds.), The Johns Hopkins University Press, Baltimore, MD.

18 National Research Council 2003. Ocean Noise and Marine Mammals. National Academy Press, Washington DC

19 Weilgart, L. 2005. Underwater noise: death knell of our oceans? Accessed on

20 Hildebrand, J. 2007


22 National Research Council. 2003. Ocean Noise and Marine Mammals. National Academy of Sciences Press, Washington DC


24 P.Popham 2007. Shipping lanes moved to boost dolphin numbers

25 Millennium Ecosystem Assessment. 2005. Vol 1 Current state and trends. Coastal Systems. Pp513-549 In Ecosystems and Human Well-Bring. Island Press, Washington, DC