THE THREAT OF POLLUTION
and what YOU can do about it
TOXIC POLLUTION
| 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.
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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).
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Source
Million gallons/year
Large Spill
Accidents
37
Routine Ship Maintenance
137 |
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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).
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 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). |
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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. |
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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.
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 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. |
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| 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:
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Eutrophication (image below courtesy: PEW Ocean Commission www.pewoceans.com) 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. |
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| 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." | ||
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What can you do about it?
Images courtesy of U.S.
Environmental Protection Agency (www.epa.gov)
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Continue within our Pollution pages to read about Air Pollution. |
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Never pour any oil or other chemicals onto the
ground or into drains. 
Recycle
Reduce the use of hazardous chemicals
Consume less pesticide-dependant foods
Landscape with native plants 
Compost your household, kitchen and yard wastes,
Limit paved surfaces
Manage Septic systems properly 
Do not discharge sewage from boats
Conserve water
Your
Voice counts.