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and what YOU can do about it


Oil is perhaps the most publicly recognized toxic pollutant. Large tanker accidents like the Exxon Valdez quickly become known worldwide. Events like this, where the Exxon Valdez grounded on Bligh Reef spilling nearly 11 million gallons of oil into the Prince William Sound in March of 1989, are dramatic and devastating to the entire surrounding marine ecosystem for many years.

The grounding of the Valdez may have been one of the most publicized tanker accidents in recent history, but there are many events like this which have occurred.  The biggest spill ever recorded happened during the 1991 Persian Gulf War when about 240 million gallons spilled from oil terminals and tankers off the coast of Saudi Arabia. Image of the Exxon Valdez courtesy of NOAA (


Many people don't realize that hundreds of millions of gallons each year quietly end up in our oceans by sources.  The following list shows how much oil reaches  our oceans from other sources. (Figures from National Research Council,  2002).


Source                  Million gallons/year

Large Spill Accidents                     37           Routine Ship Maintenance            137
Drains and Runoff                        363
From Air Pollution                         92
Natural seepage                             62
Offshore Drilling                             15


These sources result in an estimated average of 706 million gallons of oil pollution entering our oceans each year.  Of this, less than 10%  is from natural seepage of oil from the ocean floor and eroding of sedimentary rock. The remaining 644 million gallons comes from human activities. Offshore drilling, as a result of accidental spills and other operations, accounts for just over 2%. Large tanker spills, which are reported the world over, account for just over 5%. Air pollution from cars and industry accounts for just over 13% of the total, as the hundreds of tons of hydrocarbons land in our oceans from particle fallout aided by the rain, which washes the particles from the air.  Almost 4 times the amount of oil which comes from the large tanker spills, 19%,  is regularly released into the ocean from routine maintenance, which includes boat bilge discharge as well as other ship operations. By far, the greatest cause of oil in our oceans comes from drains and urban street runoff. Much of this is from improper disposal of engine oil. An average oil change uses 5 quarts  of oil, which alone can contaminate millions of gallons of fresh water. More than half of all Americans change their own oil but only about one-third of the used oil from do-it-yourself oil changes is collected and recycled (U.S. Environmental Protection Agency, 1989). In fact, the yearly road runoff from a city of 5 million could contain as much oil as one large tanker spill (Smithsonian Institution, 1995).


Crude oil from tanker accidents and offshore drilling is most likely to cause problems that are immediately obvious. Most people have seen the images of oil-coated animals and the large oil slicks surrounding the tankers after an accident. As the picture on the right shows (NASA, Jet Propulsion Laboratory) the oil will spread over large areas often continuing to cause harm for many years. When quantities of surface oil are sufficient to coat animal fur and feathers, the animals cannot stay warm and will ingest the toxic oil while attempting to clean themselves.  Many of these oiled animals will freeze to death or die as a result of ingesting these toxins.  Many marine animals that do not die quickly as a result of the oil spill may develop liver disease and reproductive and growth problems because of ingestion. Even very small quantities of oil will spread, floating on the surface of the water covering vast areas of water.  These thin sheets can kill marine larvae which in turn will reduce the number of marine animals. Effects on human populations are realized through potential health hazards as well as economic losses, such as those associated with the loss of fisheries or tourism. Particularly susceptible to injury from releases of oil are exposed shorelines, shallow reef environments, estuaries, mangrove forests, and wetlands (U.S. EPA, 1994).

Thousands of other pollutants also end up in the ocean. More than 2.8 billion gallons of industrial waste water per day are discharged directly into U.S. ocean waters (U.S. EPA, 1994), excluding electric utilities and offshore oil and gas effluents. Heavy metals released from industry, such as mercury and lead, are often found in marine life, including many of those often consumed by humans. The longer-lived, larger fish such as king mackerel, tilefish, swordfish and shark often contain harmful levels of the pollutant mercury which can harm the developing brain and nervous system of children and fetuses. (For more information, see the Air Pollution area). The list of dangerous chemical pollutants is long, including chemical contaminants like pesticides, pharmaceutical agents, and biological contaminants like bacteria, viruses, and protozoa.  Dioxins from the pulp and paper bleaching process can cause genetic chromosomal degradation in marine animals and may even cause cancer in humans. PCB's (polychlorinated biphenyls), which usually come from older electrical equipment, typically cause reproduction problems in most marine organisms. Poly-aromatic hydrocarbons (PAH) are another source of marine toxic pollution and typically come from oil pollution and burning wood and coal. These PAH's are responsible for causing genetic chromosomal aberrations in many marine animals. 

Cyanide fishing is a practice still widely used to catch live aquarium fish in the South Pacific and Southeast Asia. Fishermen stun fish by squirting cyanide into the reef areas where these fish seek refuge. They then rip apart the reefs with crowbars to capture disoriented fish. But cyanide is also a killer of coral polyps and the symbiotic algae and other small organisms necessary for healthy oceans. 


Many cruise ships have become more like floating cities, transporting millions of people into the most pristine ocean environments around the world. They have been operating with little to no environmental regulations. The lack of regulation by this industry has caused a great deal of damage to sensitive marine environments and is of growing concern as the industry is rapidly expanding. Ships have grown from typically accommodating 600-700 people in 1970 to ships that now carry over 5000 people. A typical 3000 passenger ship can produce 255,000 gallons of wastewater and 30,000 gallons of sewage every day (The Ocean Conservancy,2002, p 13 & 15). All of this waste is normally discharged directly into the ocean and it is legal to do so in most areas provided the boats discharge 3 nautical miles from the coast. This waste can contain bacteria, pathogens, medical waste, oils, detergents, cleaners, heavy metals, harmful nutrients (nitrogen amongst others) and other substances.  These substances can be brought back to coastal areas as well as cause serious damage to the aquatic life further out in the sea, including posing a risk for contaminating seafood. Nitrogen compounds can also contribute to environmentally hazardous algae blooms. Typically 75-85% of the solid waste from a ship is incinerated at sea adding to sea pollution as the toxins and ash settles back into the ocean. Additionally, habitat alteration is a common occurrence where cruise ships use anchoring systems.  The sheer size and weight of an anchor dramatically disturbs the seafloor.
Some cruise lines have now worked to introduce and use more environmentally responsible methods. However, there remains a lack of laws and those laws that do exist, are inadequately enforced.

Another serious type of  marine pollution is nutrient pollution.  This pollution is caused primarily from agricultural runoff that contains fertilizers and growth stimulants as well as from airborne nitrogen compounds that comes from automobile exhaust, industrial pollution and ammonia from manure. This has long been considered a problem in freshwater systems. In recent years, scientists have become more concerned about eutrophic (overly nutrient enriched) conditions in coastal estuaries. Nutrient pollution now represents the most widespread pollution problem facing U.S. coastal waters (National Centers for Coastal Ocean Science, National Oceanic and Atmospheric Administration, 2003, p. 11). Nutrient pollution causes many problems, including:

  • Harmful algal blooms
  • Hypoxic areas or "dead zones"
  • Fish kills
  • Loss of seagrass and kelp beds
  • Coral reef destruction
  • Eutrophication.

Eutrophication (image below courtesy: PEW Ocean Commission is a condition in an aquatic ecosystem where high nutrient concentrations stimulate blooms of algae (e.g., phytoplankton).  The main cause of eutrophication is excess nitrogen run-off from farm fertilizers, sewage and industrial pollutants. Eutrophication reduces water clarity and depletes oxygen. Reduced water clarity can starve sea grasses and algae that live in corals from light, reducing their growth or killing them. While wind and waves aerate surface waters, the pycnocline—a layer of rapid change in water temperature and density—acts as a barrier to oxygen exchange in bottom waters.

Excess phytoplankton reduces water clarity and consumes oxygen. Phytoplankton need nutrients as well as the energy from the sun to survive but too many nutrients can cause algae blooms and, in turn, red tides (dying phytoplankton). In some regions (particularly near major rivers), excess nutrients can be added to the coastal zone as a result of fertilizer runoff, sewage, animal feedlot runoff, or air pollution. During the bloom, the phytoplankton consume nutrients and oxygen which, in turn, causes a decrease in the amount of dissolved nitrogen and phosphorus in the water body.  As the nutrients become depleted, the algae can no longer survive.  The dead phytoplankton sink to the bottom of the water column where they are consumed by decomposers. Since these decomposers require oxygen to break down the algae, dissolved oxygen levels will decrease during this time period. Resulting low oxygen levels can be detrimental to fish health; if dissolved oxygen drops to below 2 mg/l, mass fish kills can result. This is known as hypoxia. The areas in which hypoxia has occurred are known as 'Dead Zones.' Dead zones have been a factor in the Gulf of Mexico and Chesapeake Bay on the U.S. east coast, and are now spreading to other bodies of water, including the Baltic Sea, Black Sea, Adriatic Sea, Gulf of Thailand and Yellow Sea. There are now nearly 150 dead zones around the globe-- double the number in 1990, with some extending 27,000 square miles (United Nations Environment Programme, 2003). The article states that "Unless urgent action is taken to tackle the sources of the problem, it is likely to escalate rapidly."

What can you do about it?

  • Never pour any oil or other chemicals onto the ground or into drains.  Many of these chemicals make their way to the ocean. Even if you live far from the ocean, the chemicals from your area can be transported to the ocean in streams and rivers. Maintain your vehicles to prevent oil from leaking onto the road which will then go down a drain and into the water.
  •     Recycle all oil and chemicals. Most communities have recycling centers that will accept used oil and other chemicals for recycling.
  • Reduce the use of hazardous chemicals by choosing household cleaners, pesticides and fertilizers which are not toxic to your surroundings. If chemicals are toxic to the oceans, they are also a danger to you and your family. Look at our Non-Toxic and Natural Page for possible alternatives.
  • Consume less pesticide-dependant foods thereby reducing the amount of pesticides used.
  •     Landscape with native plants that do not require fertilizers and that need less water. Less irrigation results in less runoff, while less chemical application keeps runoff clean.
  •     Compost your household, kitchen and yard wastes, which makes an excellent fertilizer.
  •     Limit paved surfaces as they prevent water from percolating down into the ground, causing runoff to accumulate. Paved surfaces also transfer heat to runoff, thereby increasing the temperature of receiving waters. Native species of fish and other aquatic life cannot survive in these warmer waters.

Images courtesy of U.S. Environmental Protection Agency (

  • Manage Septic systems properly since overflowing and malfunctioning septic and sewer systems release bacteria and nutrients into the water cycle.
  •   Do not discharge sewage from boats into coastal waters.  Use pump-out stations.  Report any malicious dumping that you witness.  Within US waters, call the U.S. Coast Guard at 800-424-8802.  Be sure to note the date, time, and location of the incident.
  • Choose cruise ships with sound environmental practices.  If you are planning to vacation on a cruise lines, first ask what systems they use to preserve the environments, if and how they discharge waste and what recycling programs they have in place.
  •    Conserve water by purchasing water-efficient showerheads, faucets, and toilets which will reduce the total amount of wastewater and lessen the total runoff.
  • Your Voice counts. Use our letter writing area to make sure your opinions and concerns are heard by government and industry.


Continue within our Pollution pages to read about Air Pollution.

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