Plastic pollution: which two oceans contain the most?

Plastic is a big problem in our oceans. According to the most comprehensive study undertaken so far, there are 5 trillion pieces of plastic floating in the sea.

The ocean with the largest amount of plastic is the North Pacific, followed by the Indian Ocean, the North Atlantic, the South Pacific, the South Atlantic and the Mediterranean Sea.

While you might imagine a scene the equivalent of a floating landfill, actually much of the plastic is barely visible. Among the most common items are the tiny beads that go into cosmetic products, such as toothpastes and facial scrubs.

Other pieces are much larger and made from hard plastic, such as discarded toys and fishing equipment.

Altogether, the plastic waste in our oceans weighs as much as 268,000 tons, which is equivalent to 38,000 African elephants.

Drowning in debris

Ocean researcher Marcus Eriksen is credited with revealing the scale of the problem for the first time, in a paper published in 2014.

In 24 expeditions over six years, Erikson and his team from the 5Gyres Institute collected data from the oceans to construct the size and weight of the plastic problem. They did this by measuring the amount of waste in ocean "gyres", natural vortexes of wind and marine currents that draw debris to their centres.

The gyre in the North Pacific represents one-third of the plastic pollution in all oceans, with an estimated 2 trillion pieces. In fact, the so-called Great Pacific Garbage Patch is already a well-documented phenomenon, having been discovered by Charles Moore in 1997.

With 1.3 trillion pieces, the Indian Ocean has the second-largest volume of plastic. Third is the North Atlantic, with 930 billion pieces; fourth is the South Pacific, with 491 billion pieces; and fifth is the South Atlantic, with 297 billion pieces. The Mediterranean Sea, the smallest of all, holds about 247 billion pieces.

The Northern Hemisphere is worse afflicted than its southern counterpart: the North Pacific and Indian oceans contain 56% of all particles.

Where is all the plastic from?

It is estimated that around 80% of the world's plastic pollution comes from land-based use, and around 20% from marine-going vessels.

Discarded plastic is blown from overfilled garbage cans, from landfills and from vehicles; much of it ending up in rivers and streams, which then carry the items into the ocean. Much of the plastic is also discarded on beaches and shorelines, and ends up in the water.

Ocean-going vessels dump waste in the water and storms can cause ships to lose their cargo.

Why does it matter?

Eriksen and his team categorized the plastic by their different sizes: micro plastics (4.75 millimetres and under), meso plastics (4.75 to 200mm) and macro plastics (over 200mm).

They found that most of the waste fell into the micro plastics category, whether they were created that way (such as microbeads) or because larger pieces had broken down over time.

It can take decades for the plastic to break down fully, and in that time they can cause a lot of damage. Sea creatures ingest small plastic pieces, which can make them sick or kill them. (The plastic can even be passed to us when we eat the fish.) Other marine animals get caught in pieces of plastic and die as a result.

Tip of the iceberg?

On top of this, it seems the plastic found by Eriksen and his team is not the whole story. A reported 288 million tons of plastic was produced worldwide in 2012, according to Plastics Europe, a trade organization representing plastic producers and manufactures.

This means the team’s estimate of total global plastic pollution is only 0.1% of the world's annual output, suggesting that the actual figure may be much higher.

“Our estimates of macro plastic are based on a limited inventory of ocean observations,” said Eriksen. “They also do not account for the potentially massive amount of plastic present on shorelines, on the seabed, suspended in the water column, and within organisms.”

Whilst scientists agree that trying to clean up the waste in the ocean is currently an impossible task, efforts have been diverted into reducing our use of disposable plastics in favour of biodegradable sources.

In the meantime, further research from Kings College London has suggested that plastic may now be entering the air we breathe, making the issue even more urgent.

Have you read?

How much plastic is in the ocean?
How to stop plastic becoming waste
7 reasons to clean up the sea

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