A Plastic Ocean: The Facts

Rita Steyn

We all know there’s plastic in the ocean. But how much is there? And how does it get there? Does it float around on the oceanic currents, or does it go somewhere else? Read on to find out...

How much plastic is really in the ocean?

If you’re not convinced that there’s a significant amount of plastic in the ocean, stop right now and watch this video.

According to the Natural History Museum (UK) between 4.8 and 12.7 million tonnes of plastic enter the ocean each year. This equates to approximately 8 million pieces every day. To put that into context: that’s around one garbage truck every minute. It is estimated that there may now be around 5.25 trillion pieces of plastic floating in the open ocean, weighing up to 269,000 tonnes. And it won’t stop there! The upward trend of plastic production shows no sign of slowing, as we continue to produce more plastic year-on-year – in 2017 348 million metric tons of plastic were produced worldwide - meaning more and more plastic will continue to pollute the marine environment.

Plastic pollution is everywhere! Photo: Pixabay

Plastic pollution is everywhere! Photo: Pixabay

Where is it from?

Some plastic is dumped directly into the ocean, some is lost (such as fishing gear), carried by the wind from nearby landfills and settlements, or washed in from rivers. It has been estimated that 80% of ocean plastics are attributed to land-based sources. In a recent study of the amount of plastic litter transported into the oceans by 57 river systems worldwide, 10 rivers were estimated to be responsible for 90% of it. In other words, 90% of the plastic coming from rivers is from these 10. Eight of these rivers are in Asia: the Yangtze; Indus; Yellow; Hai He; Ganges; Pearl; Amur; Mekong; and two are in Africa – the Nile and the Niger.

Balloons blown into the ocean by the wind. Photo: Tristan Ray-Wilks @tristanraywilks

Balloons blown into the ocean by the wind. Photo: Tristan Ray-Wilks @tristanraywilks

Key factors influencing marine plastic include population size and waste management systems. Lack of proper waste management in some countries means plastics are not disposed of properly, and ultimately more ends up in rivers which carry the plastics to the sea. Without waste management infrastructure improvements, the cumulative quantity of plastic waste available to enter the ocean from land is predicted to increase by an order of magnitude by 2025.

However, we can’t just point the blame to those countries who lack the infrastructure to properly manage their waste. It is developed nations worldwide that produce the most plastic, and we are also indirectly responsible for the vast amount of marine plastic pollution. How so, you ask? Look out for our article on recycling on the 17th June to find out.

This chart shows global annual per-capita production of plastic by region. Chart from Statista.

This chart shows global annual per-capita production of plastic by region. Chart from Statista.

Where does it go?

Where doesn’t it go? Once plastic has entered the ocean ecosystem, it can be found literally everywhere. Not even the deepest, darkest areas of the oceans are safe; one litre of water collected in the Mariana Trench (about 10 km deep) contained thousands of tiny plastic pieces, and researchers even spotted a plastic bag while surveying the area using an ROV. (What’s worse, deep sea  amphipods (tiny shrimp-like crustaceans) are eating it, with 100% of individuals sampled found to contain plastic fibres.)

As plastics are generally less dense than water, they tend to float on the surface, where they are pulled around by surface currents and wind. The circulating pattern of ocean currents creates huge rotating currents known as gyres. As the water rotates it draws in more and more plastic debris, eventually forming vast soups of floating plastic like the Great Pacific Garbage Patch ( there is nothing “great” about it except for its size, which is greatly depressing). This patch of mostly small plastics is sometimes described as a “peppery soup” with bigger chunks of plastic dotted throughout. Unlike your bowl of soup though, this patch covers roughly 1.6 MILLION square kilometers – which is about twice the size of Texas, or three times the size of Spain. Similar stretches of floating debris are being found elsewhere. Such as a 5 mile long patch near Honduras.

Whilst ocean basins in the Northern Hemisphere contain the most plastic, a surprising amount is accumulating in the Southern Hemisphere, suggesting plastic is being transported between gyres and basins easily.

Just because the plastic makes it into the ocean, doesn’t mean it will just float around forever. Fish, shellfish, and seabirds all ingest plastic, some as tiny particles, and the rest as larger whole or broken plastic pieces. No organism is safe from the plastic soup - even microscopic algae (phytoplankton) and animals (zooplankton) are capable of consuming plastic! Microplastics have been found in the fish that humans eat, and subsequently have been found in our blood, and faeces!

A phenomenon which has puzzled scientists for years, is the order of magnitude mismatch between the amount of plastic entering the ocean, and the estimates of plastic pollution at the surface, dubbed the ‘missing plastic’ problem. It seems that the surface is not the ultimate sink for plastic. The increased weight of plastics due to biofouling (attachment of organisms), capture in marine snow, or aggregations with phytoplankton, leads them to sink towards the ocean floor. And when plastics are ingested, and later egested, they become trapped in faecal pellets (poo), which also drift downwards. So the sea floor may be the site of the plastic graveyard, with one study finding microplastics to be four orders of magnitude more abundant in deep-sea sediments than plastic-polluted surface waters.

Plastic finds it way into all marine environments. Photo: Andy Osborne @osbornandy

Plastic finds it way into all marine environments. Photo: Andy Osborne @osbornandy

So what can you do?

  1. Don’t despair! Collectively we created this, and collectively we will have to address it.

  2. Educate yourself, and then others. Cut down on your personal use of plastics and teach those around you how to do the same.

  3. Be the first line of defense. One of the best ways to deal with plastic pollution is to prevent it – Just say no. When you can and if you can – cut the plastic habit out completely.

  4. Pick plastic up where you see it, dispose of it properly, and never leave the beach empty handed. Volunteer, clean up, and help others to do the same.

  5. Demand more from the companies that you buy your goods and services from. Speak with your lawmakers. Use your money to support companies that are doing the right thing.

This month we’ll be sharing tips on how to live plastic free, sharing review videos on plastic free products, and shedding light on the complex issue that is plastic pollution. So keep an eye out!

This month, The Marine Diaries will be sharing our knowledge on plastic pollution to help educate the public about the impact of our actions on marine life, in the hope of promoting change. Together we can fight plastic.

Want to become part of a community striving to reduce their plastic use? Join our Facebook group