definition 112 causes, effects and control measures of

5.2.4 Marine Pollution

Marine pollution can be defined as the intro-

duction of substances to the marine environ-

ment directly or indirectly by man resulting in

adverse effects such as hazards to human health,

obstruction of marine activities and lowering the

quality of sea water. While the causes of ma-

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Environmental Studies for Undergraduate Courses

rine pollution may be similar to that of general

water pollution there are some very specific

causes that pollute marine waters.

•

The most obvious inputs of waste is through

pipes directly discharging wastes into the

sea. Very often municipal waste and sew-

age from residences and hotels in coastal

towns are directly discharged into the sea.

•

Pesticides and fertilizers from agriculture

which are washed off the land by rain, en-

ter water courses and eventually reach the

sea.

•

Petroleum and oils washed off from the

roads normally enter the sewage system but

stormwater overflows carry these materials

into rivers and eventually into the seas.

•

Ships carry many toxic substances such as

oil, liquefied natural gas, pesticides, indus-

trial chemicals, etc. in huge quantities some-

times to the capacity of 350,000 tonnes.

Ship accidents and accidental spillages at

sea therefore can be very damaging to the

marine environment. Shipping channels in

estuaries and at the entrances to ports of-

ten require frequent dredging to keep them

open. This dredged material that may con-

tain heavy metals and other contaminants

are often dumped out to sea.

•

Offshore oil exploration and extraction also

pollute the seawater to a large extent.

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Pollution