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The ocean and the plastic problem

Intermediate / Intermediate / Advanced Marine Litter 15 min

Credits marine litter

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I N T R O D U C T I O N : M A R I N E  D E B R I S  A N D  T H E  P L A S T I C  P R O B L E M

Of all the marine debris present in our oceans, plastic is the most common 1. Every year, eight million tonnes of plastic waste flow from land to sea 2. In certain parts of the globe, plastic represents up to 95% of the total marine debris 3. This omnipresence of plastic in our oceans is due to constantly increasing industrial production. In 1950, world plastic production stood at 1.5 million tonnes. In 2015, it was 322 million 4.

This increase in production is due to plastic being so cheap, resistant and easy to produce. Plastic lives on long after it has been thrown away and a large part of all plastic produced is designed for single use. A minute portion of plastic is recycled. The rest ends up either in landfill or in our environment. Plastic never fully degrades. Instead, it becomes fragmented into tiny particles, barely visible to the naked eye. These ‘microplastics’ are difficult to detect and impossible to remove completely from the environment.

How marine debris is created ?


Be it plastic, glass, fabric or metal, all litter is created by human activity. Marine litter is defined as: ‘any object or material produced by man which, directly or indirectly, ends up in the ocean 5. Marine debris is solid and resistant, be it floating, stranded or submerged. It’s classified according to its size and can be ‘macro-waste’ (>5mm) or ‘micro-waste’ (<5mm) 6.


The debris mainly comes from inland regions. It’s transported by wind, rain and waterways to the ocean. Between 1.15 and 2.41 millions of tonnes of plastic flow from rivers into the ocean every year 7. During storms or heavy rains, water levels rise, sweeping away litter from the shore. As they travel through agricultural, industrial and urban areas, waterways pick up a multitude of litter (food packaging, tin cans, cigarette butts, etc...). In towns and cities, water treatment infrastructure can become overloaded, meaning untreated waste water ends up in the local ecosystem. Fish farming, fishing and maritime transport also contribute to the waste abandoned on beaches or out at sea. 

The movement of marine debris in the ocean


Litter transported by wind, rain and waterways finds its way into the ocean. A tiny part of this waste drifts onto our beaches, but the majority of it sinks to the bottom of the ocean 8. Floating debris can be carried by ocean currents across sometimes remarkable distances. Of all this debris, plastic is the most problematic for the environment. It becomes fragmented into micro particles by the UV effect and micro bacteria 9. Today there are over 5000 billion plastic particles floating in our oceans 10. Marine currents play a crucial role in the transport and distribution of ocean waste on a global scale. This is why certain waste products can be found in areas with little or no human activity. Large quantities of plastic debris can be found in the Arctic, for example. Ocean currents are essentially highways for litter.

A  S E V E N T H    C O N T I N E N T  O F  W A S T E ?

The Seventh Continent, also called the Great Pacific Garbage Patch, is a zone where floating debris converges, situated in the North Pacific between California and Japan. There are 5 such meeting points or ‘gyres’ on earth. Taking the form of a plastic soup, these gyres are essentially made up of plastic particles smaller than 5mm. It is estimated that the Great Pacific Garbage Patch or Seventh Continent could contain between 45 and 129 thousand tonnes of waste 11.