1. Introduction

What is Marine Pollution?

"That's obviously the contamination of sea water" you may think.

And, of course, you are perfectly right! But - what does it take to pollute water? And how much of it is needed for it to be harmful?

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plastic bottle at the bottom of the ocean
A plastic bottle at the bottom of the Western Pacific.
Photo: Wolcott Henry 2005 / Marine Photobank
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algal bloom
Image of red tide in Gulf of Mexico in 2001.
Photo: NOAA
Does a plastic bottle at the bottom of the ocean harm marine wildlife? Are harmful algae a form of pollution even though they are plants?
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natural petroleum seep
Petroleum seep with oil and gas rising to the surface. The seep began after the 1994 Northridge earthquake in the North Sulphur Mountain Area of Ojai oil field, Ventura County, California.
Photo: S. Mulqueen, State of California, Dep. of Conservation
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sinking tanker with chemicals aboard
Chemicals can enter the sea deliberately or as a consequence of accidents as exemplified by this sinking ship. The photograph shows the vessel 'New Flame' after a collision off Europa Point, the southernmost tip of Gibraltar, in August 2007.
Photo: David Parody / Marine Photobank
Do oil spills that originate from natural oil seeps pollute the sea water? Are chemicals spillt at sea harmful even if we don't see them?


There are a few things to think about:

  • Does the nature of the substance (the pollutant) make a difference? (whether it is a plastic water bottle or a tin)
  • Does the amount of the substance play a role? (whether it is one bottle or two)
  • Are humans involved or is there such a thing as 'natural pollution'? (e.g. in the form of harmful algae or natural oil seeps)

What do you think?

As you can imagine people had to agree on what marine pollution is in order to be able to prevent and combat it.

This is the definition of marine pollution commonly used:

Direct or indirect introduction by humans of substances or energy into the marine environment (including estuaries), resulting in harm to living resources, hazards to human health, hindrances to marine activities including fishing, impairment of the quality of sea water and reduction of amenities.

Source: United Nations, Glossary of environment statistics