Skip main navigation

New offer! Get 30% off one whole year of Unlimited learning. Subscribe for just £249.99 £174.99. New subscribers only T&Cs apply

Find out more

Out of sight, out of mind?

Prof Paul Tyler MBE explains what happens to our rubbish in the deep-sea environment
PROFESSOR EMERITUS PAUL TYLER: The deep ocean has being used for disposal of waste for many years now. One of the first things disposed of in the ocean was clinker. We rarely see clinker nowadays, but it’s the product of burning coal. If you burn coal in a fire, you’re left with a very hard waste. And in the era of steam ships from the early 19th century onwards, this waste was literally heaved over the side of the ship as the boilers were cleaned out. And, essentially, clinker is found very commonly where the old shipping routes were. You know, Southampton to New York, through the Mediterranean, down to South America.
And it’s quite toxic material because it’s got all sorts of trace metals in it. But animals do appear to inhabit it. And in some cases, we found anemones growing on clinker. The other stuff that’s been deposited in the deep sea over the years is low level radioactive waste. And this is the by-products of, particularly, medical research, white coats, things like that. And they’ve been put into drums, sealed, and, to be frank, just heaved over the side of ships and left on the sea bed. That was stopped some years ago, so that’s not happening nowadays. But there is still the problem of the disposal of high level radioactive waste.
The modern disposal in the deep sea appears to be very much associated with litter. And litter comes in various forms. It can be drinks cans, it can be bottles, it can just be magazines. But it can be oil drums. It can be fishing gear. A whole variety of things can be disposed of in the sea. But one of the main problems that’s disposed of is plastic because plastic doesn’t break down very easily. It breaks down eventually, and it forms a very small particles that go by the name of mermaids tears. And these are found in sediment, and they break down, and eventually they actually still release chemicals even when they’re very, very small.
And you find plastic in virtually every trawl that are taken on the sea bed. And this is particularly common, again, associated with shipping routes. You see this in the Mediterranean, particularly, and you see it in places like canyons off major cities. And we’ve seen this in Lisbon Canyon off Lisbon on the west coast of Portugal. And the plastic breaks down very slowly. And what it does, if you take an example of a plastic bag, it tends to trap sediment. And when that sediment is trapped, it’s not aerated, and eventually it becomes anoxic, and so you have no animals living in it.
Other litter, like fishing gear, on a short term, might actually improve the biodiversity because it’s maybe metallic and you get something settling on it that would not normally live in that part of the environment. The fourth aspect is really something that may well happen in the future, and that’s the disposal of CO2. Under certain conditions, carbon dioxide will be liquid at certain temperatures and certain pressures. And there is some thoughts of disposing of carbon dioxide in the deep sea as lakes in the deepest parts of the oceans. It would be liquefied at the surface and then pumped down into the deep sea.
And the reason the deep sea is such an attractive proposition to some people for the disposal of waste is it is out of sight, therefore it’s out of mind. But, essentially, it is doing damage to the deep sea as we speak. Often the disposal of waste, particularly litter into the deep sea, is as a function of people’s thoughtlessness. And we had a very weird example many years ago. We were diving in the Bahamas down to about 600 metres, and we were going along the slope there. We came to a relatively flat bit, and there was a castle there. And I looked at the pilot and said, “Am I seeing things?” And he says, “No, it’s a castle there.”
And what it was, what we think it was anyway, was a castle that has been used for a production on one of the cruise ships that goes around the Bahamas regularly. And when they’d finished with it, quite thoughtlessly, they had just thrown it over the side of the ship, and it had obviously sunk fairly quickly. And it had found one of the few flat places around the Bahamas to settle, and it settled on the sea bed. And it looked just like a castle as you came up to it in the submersible.

Rubbish and litter strewn along beaches is unfortunately a common sight. The litter poll in the previous step is based on data from the Ocean Conservancy 2018 Cleanup Report.
In fact, cigarette butts were the most numerous with approximately 2,412,151 collected during the cleanup. However, this is rubbish collected from beaches and waterways. There are also types of pollutants which are finding their way into the deep ocean.

You may remember that in Week 2 Professor Mark Brandon talked about how the ocean currents can transport litter great distances around the globe, but our rubbish isn’t just moved around on the surface of the ocean. The deep sea is no longer a pristine environment untouched by the presence of humans, and it hasn’t been for quite some time. From clinker produced as waste by steam-powered ships in the 1800s, to modern day soft drink cans and plastics, the ocean floor has been affected by our garbage. There are also more unusual examples of rubbish ending up in the deep ocean, as Professor Paul Tyler MBE explains what happens to our rubbish in the video for this Step.

We’ve looked at some historical and modern impacts that we’ve had on the deep ocean. Now use some of the links below to read more about human impacts in the deep ocean, and share your response to the question below with other learners in the comments section.

In 2018 the Government’s cross-party Environmental Audit Committee carried out an enquiry into Sustainable Seas, including plastics and other pollutants in the ocean. The report summarises a huge amount of evidence including evidence from our course lead Rachel Mills and Jon Copley.

Many organisations are prioritising tackling the global problem of marine litter, including Surfers Against Sewage who have produced a marine litter report

The Pew Foundation has documented the impact of plastics on the life in the oceans and this report shows us the gruesome impact of plastic debris on marine animals.

Here are some supplementary, more advanced readings if you would like to explore these topics in more depth:

A useful review of plastics in the marine environment

This paper demonstrates that the vast majority of microplastics in the oceans end up on the seafloor and are focussed by bottom currents into canyons and trenches – areas which are also hot spots for deep sea life.

Human impacts in the deep sea

What do you think is the most significant human impact in the deep ocean today?

This article is from the free online

Exploring Our Ocean

Created by
FutureLearn - Learning For Life

Reach your personal and professional goals

Unlock access to hundreds of expert online courses and degrees from top universities and educators to gain accredited qualifications and professional CV-building certificates.

Join over 18 million learners to launch, switch or build upon your career, all at your own pace, across a wide range of topic areas.

Start Learning now