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Causes
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Accidental and deliberate discharge of crude oil into the ocean by cargo ships is regarded as one of the
prime causes of pollution of the water body.
Dumping of industrial wastes into ocean is another reason for marine pollution. The wastes often contain
toxic materials such as mercury, dioxin, PCBs, PAHs and radioactive materials, which contaminate the
water of ocean.
Deposition of sediments from mining leads to ocean pollution.
Trash washed into the ocean after heavy rain or floods gives rise to marine debris, which pollutes the water
body.
Dumping of human wastes, plastic and disposal of untreated or partially treated sewage water into the
ocean is called 'garbage dumping'. This is one of the leading causes of marine pollution.
Carbon dioxide, emitted by automobiles, due to the burning of fossil fuels, leads to air pollution. The
contaminated air containing carbon dioxide reaches the ocean in the form of acid rain, thereby polluting the
water.
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Marine Pollution: Causes and Consequences
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Pollution of the world's oceans is quickly becoming a major problem on Earth. We know very
little about the effect that pollution has on the oceans, but we continue to dispose off chemicals,
sewage and garbage into it at an unprecedented rate. Most people likely do not even know what
types of pollutants reach the oceans. There may be billions of people unconcerned about ocean
pollution and hence this problem. Truly, the fish catch from the sea will tend to bio concentrate
the pollutants to finally reach the humans.
Toxic Ocean Pollutants
Toxic pollutants in the ocean ecosystem have massive impacts on the plants and
animals. Heavy metal poisoning (such as lead and mercury) from industrial effluents accumulate
in the tissues of top predators such as whales and sharks (so do not hesitate to support ban of
hunting whales and sharks but to the dislike of many others). Many a times such poisoning
causes birth defects and damages nervous system. Dioxins from the pulp and paper bleaching
process can cause genetic chromosomal problems in marine animals and may even cause cancer
in humans. PCBs (polychlorinated biphenyls) typically cause reproduction problems in most
marine organisms. PCBs usually come from older electrical equipment.
Poly-aromatic hydrocarbons (PAHs) are another source of marine toxic pollution and
typically come from oil pollution and burning wood and coal. These PAHs are responsible for
causing genetic chromosomal aberrations in many marine animals. Lastly, low-level radiation
poisoning is also possible in the ocean environment. Though scientists know very little about
how radiation affects marine organisms, it cannot be a good thing anyway. Some marine species
such as a population of Beluga whales living in the St. Lawrence River area in Eastern
Canada are in serious trouble because of marine toxic pollution. These Beluga whales are the
victims of ocean pollution ranging from PCBs to heavy metals as well as other
pollutants. However, toxic pollution is only the tip of the iceberg in terms of total ocean
pollution.
The toxic pollution varies from PAHs heavy metal pollution from industrial effluent and
fallout, PCB pollution and even possible low level radiation. No matter what we humans do,
there is potential for serious pollution of the oceans.
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Marine Garbage
Marine garbage disposal is another major form of ocean pollution. The world's oceans are a
virtual dumping ground for trash. Sometimes the garbage includes junked out fishing nets,
plastics, general household garbage and even like bulbs. In one case, an island 300 miles from
the nearest inhabited island (and 3000+ miles from the nearest continent) had 950 pieces of
garbage ranging from plastics to tin cans.
Garbage in the oceans is a serious issue as fish entangle themselves in fishing nets and
animals sometimes eat trash products and die. There are numerous examples of dolphins, sharks
and whales entangling themselves in fishing nets and dying from oxygen starvation. It is possible
to clean garbage from the oceans if humanity quits using it as a garbage dump. Marine garbage
can often enter into animal gut; plastic pop tab rings accidentally strangle animals and so
forth. Controlling this form of pollution is important to maintain a healthy ocean ecosystem.
Even simple plastic bags can have large pollutive impacts within the ocean. In one case, a
deceased sperm whale was found to have a party balloon blocking its digestive system. The
whale died from inability to process its food and died of starvation. Plastics can also have
negative impacts to boats if they accidentally plug water intake lines.
Sewage Disposal in Ocean
Sewage is yet another major source of marine pollution. Typically, the problem with sewage
is that it causes massive nutrient loading in the ocean ecosystem. Nutrient loading triggers algal
blooms in the water leading to the loss of dissolved oxygen. After the depletion of oxygen levels,
many organisms in the ocean die from being unable to breathe properly. Other problems
associated with sewage include parasites/bacteria that force closure of public coastal beaches and
poisoning of shellfish fisheries. For the most part, cities in the developed world have sewage
treatment facilities but many of the cities in poorer areas have little to no sewage treatment. As
the world population continues to increase, sewage pollution will be on the rise.
What we often do not realize is that the waste water out of washing our clothes, faces, dishes
and cattle, is ultimately headed to the sea. This includes everything from our homes (toilets,
washing machines, bathtubs, dishwashers and so forth), industrial effluents and even chemicals
such as paints and fertilizers that we dispose of down the drains. Eventually, all of this sewage
pollution adds up and we land in serious problems due to lack of oxygen for organisms and
poisoned water.
Non-Point Pollutants
The last major source of ocean pollutant is non-point. Non-point pollution can come from
amazingly varying sources, viz., runoff from farmland (fertilizers, manure), industrial runoff
(heavy metals, phosphorous), urban runoff (oils, salts, various chemicals) and atmospheric fallout
of airborne pollution. Obviously, it is the hardest to control. Point pollution, in contrast, is
pollution from a direct source like a factory outfall pipe.
The enrichment of water by nutrients, especially compounds of nitrogen and phosphorus,
causes an accelerated growth of algae and higher forms of plant life to produce an undesirable
disturbance to the balance of organisms and the quality of the water (Eutrophication). Input of
nutrients like nitrogen and phosphorus to the sea is a natural prerequisite for life, not an
environmental problem. It becomes a problem only when the input increases to such levels that
the original properties or functions of the ecosystem change. Then, it becomes too much of a
good thing. When this manifests in marine waters or a lake, it is referred to as eutrophication - a
concept covering a series of events in the aquatic environment. Input of too large amounts of
nutrients, followed by other events and effects is ominous and results in higher levels of nutrients
in the water. Physical, chemical and biological changes that follow tend to reflect in the fauna and
flora, oxygen conditions change and other changes in the water mass, in the sediments and on the
surface of the bottoms.
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Pollution of coastal waters: Kerala under microscope
The coastal waters of the maritime states are under the constant threat of pollution from a
number of sources. The relatively long shoreline of India (6000 Km) is no exception
either. More so is the case of Kerala. Compared to the rest of the union, profile
of Kerala's coastal waters may be better; still a lot remains to be achieved. The tropicality of the
region and consequent intense rain fall in the hinterland, along with the physiography has
immensely contributed to the quality of coastal waters.
The agrarian nature of land use itself has become a bane to the coastal water bodies of the
state in the midland as well as in the lagoons in coastal land. Fertilizer residue originating from
the tea, cardamom, and rubber plantations of the highland and midland are finally headed to the
coastal water of the ocean. But, the brunt is borne by the waters in the lagoons, ponds and other
inland water bodies. The intracoastal water way is no exception either. Obviously, the fertilizer
residue leads to the eutrophication of the coastal waters, and adds to the reservoir of the
chemicals that already exists in the sea.
Luckily, the amphibious plant species that characterize the fresh water bodies and lead to
their eutrophication, do not survive in the marine environment. However, if not checked, we may
reach a situation like in the mouth ofMississippi River, where a 60 mile wide algal belt has
reportedly come to stay. The sheer size of the coastal waters is an insurance against the
pollutants, like the fertilizer residues, yet could not influence the sea water chemistry to any great
extent.
Where do we go from here?
Industrial pollution is not as bad as it used to be in the developed world as new techniques and
better waste and effluent treatment are put in place. New laws and regulations make it difficult
for people to dump their trash into the oceans though inevitably some dumping will always
occur. One idea is to promote community beach-cleaning events where in everybody volunteers
in to pick trash off the beaches. By cleaning up the trash on beaches, we lessen the potential
chances of accidental animal kills and afford better and cleaner looks for beaches.
Reduction of sewage is possible through the installation of better sewage treatment facilities
and by adoption of volume reduction technologies for the world's cities. Developed countries
like Canada and the United States as well as Western Europe should assist the poorer countries in
installing sewage treatment facilities. Reducing harmful sewage discharge would be a major start
in helping to clean the oceans of pollution. Many areas of the world have reduced non-point
pollution through proper recycling facilities for used oil and paint products. In the past, people
simply dumped used oils and paints into the sewer system where they would do serious damage
to the water. Pollution will still occur but with effort and determination it is possible to reduce its
impact on the oceans.
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(Source: Marine Ecosystem: EMCBTAP-ENVIS Newsletter, Department of Geology,
University of Kerala, Kariavattom - 695 581 Vol. 1, No. 2, 2003)