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Skip to 0 minutes and 8 secondsPROFESSOR 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.

Skip to 0 minutes and 51 secondsAnd 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.

Skip to 1 minute and 36 secondsThe 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.

Skip to 2 minutes and 20 secondsAnd 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.

Skip to 3 minutes and 0 secondsOther 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.

Skip to 3 minutes and 42 secondsAnd 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."

Skip to 4 minutes and 25 secondsAnd 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.

Out of sight, out of mind?

Rubbish and litter strewn along beaches is unfortunately a common sight. You may remember that in Week 2 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 sea, as Paul explains…

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This video is from the free online course:

Exploring Our Oceans

University of Southampton

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