2. Oil Pollution

How does oil get into the seas?

The graphic below shows the percentage of oil input to the sea through ships and other sea based activities as well as oil from natural sources (seeps).

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sources of oil input to the sea
The estimated average annual inputs of oil entering the marine environment from ships and other sea-based activities in the 10 year period 1988 - 1997
Data source: GESAMP Report and Studies No 75 (2007)
How much is that in tonnes? ↓


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new flame vessel sinking
After collision in August 2007, the vessel New Flame sinks and hits a reef. Prompt action by the Government of Gibraltar prevents major environmental damage.
Photo: David Parody / Marine Photobank

Approximately 165,000 tonnes of oil per year are spillt into the sea following shipping accidents. This is equivalent to 13.25% of the total amount of oil input to the sea through sea based activities.







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vessel illegally discharging
Aerial view of a vessel illegally discharging.
Photo: Cèdre 2007: 37

Another 206,000 tonnes of oil (16.54%) are released each year due to routine operational discharges; 186,000 tonnes (14.94%) of which is fuel sludge from vessels.
Other sources of oil input to the sea by ships includes deliberate dumping of waste oil.



Although it may be difficult to imagine, most of the oil input to the marine environment (about 70%) actually originates from land based activities!

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pump jack
A pumpjack in Texas.
Photo: Flcelloguy / Wikimedia Commons

Many spillages of oil and petroleum products occur every day all over the world, when filling, emptying and cleaning tanks or pipes, or in the everyday running of factories, pipelines, or oil wells on land. These spills may result from technical failure, negligence, vandalism, accidents or armed conflict.



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Pipeline network in Venezuela
Pipeline network in Venezuela.
Photo: Cedre 2007: 29

After a spill, the majority of the product evaporates and the rest is biodegraded during its journey as run-off or through the sewer or drainage system.
Other more persistent substances may flow into this system and end up in the sea, where they contribute to shoreline pollution by forming sheen, tar balls and patches (Cedre 2007).

The following animation shows the different paths that hydrocarbons may take until they end up in the sea.
Click the image to start (external application; opens in a new window)

Animation: Sources of Oil Pollution
Source: Cedre
Design: Hippocampe.com