THE BBC documentary series brought the startling and diverse creatures of the deep sea to our screens more intimately than ever before. It featured the first ever dive to 1000 metres in the Antarctic, and ended with a warning about our impact on the oceans – particularly from plastic pollution. Marine biologist Jon Copley at the University of Southampton, UK, was a scientific adviser on the series and was on board the Antarctic sub for filming.
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When was your first dive in a submersible?
It was an expedition with the US Navy’s deep submergence unit in the north-east Pacific 23 years ago. As it was a military unit, they inevitably liked to freak out scientists. When we reached the bottom, the pilot stood up and undid the hatch. But of course, the water pressure was holding it in place.
It was an astonishing experience because the landscape is so different down there. I didn’t want to leave.
What is it like to be in a tiny submersible for hours?
It’s cramped and cold. If you are looking for hydrothermal vents on the ocean floor, they are typically 2000 to 5000 metres deep, so it is an 8 to 12-hour dive. If you need to wee, you do it in a bottle. I’ve been on several trips where submersible pilots have had issues with kidney stones. I think this is because they avoid drinking.
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What did you see when that didn’t end up in the final show?
My favourite was the Antarctic sun starfish (pictured), which we nicknamed the death star. Unlike starfish on UK shores that have five arms, this has got about 50. What’s unusual is how it feeds. Rather than smothering its prey, it waves its arms up into the water to catch krill. The upper surface of the arms is covered in tiny pincers that snap shut when something brushes past. It was a challenge to film because the krill followed our submersible’s lights. If we stopped the sub, the krill swarmed around us. By the time we were ready to film the death star, its arms were already full of krill because we had inadvertently brought it this amazing dinner.
Blue Planet II showed a moment when your sub started leaking. Everyone seemed surprisingly calm about it.
The metal-hulled subs have portholes with a seal around them. Many of them require high pressure to work properly, so they leak a bit on the way down. What scares me most in a sub is fire. You are in a tiny, enclosed atmosphere. It could just be smoke from something electrical overheating, but that atmosphere will turn toxic fast, which is why we carry backup breathing gear and eye protection.
Why send humans down into the depths rather than just using remotely operated subs?
The remotely operated vehicles (ROVs) are superb now. Several ships are able to live-stream high-definition video from one. I can sit at home in the middle of the night with my laptop, watching live images from the bottom of the Pacific Ocean and interacting with the team on the ship. That’s amazing.
Yet there is something special about immersing yourself in the environment you are trying to understand. It might sound anachronistic, but NASA hasn’t given up on that ambition either.
“It’s special to be immersed in the environment you are trying to understand”
What else did you learn on the Antarctic expedition?
I became aware of the importance of “drop stones”. When the front of a glacier breaks off and forms an iceberg, it often has rocks stuck in its underside, which vary from the size of a fist to as big as a house. Eventually those rocks drop off. There was an exciting moment when our camera sub was filming something on the seabed and a fist-sized piece of rock dropped through the frame. If something bigger had hit the ROV, that could have been an issue!
Most of the Antarctic seabed is rich, soft mud because it is mostly krill poo. Then a drop stone arrives and it is a rocky island in that landscape. A lot of marine life requires a hard surface to live on. In the Antarctic, that is mainly supplied by drop stones.
Blue Planet II brought the deep sea to people’s attention a bit more. Do you think people’s attitudes to the oceans have changed recently?
To a lot of people, the deep sea embodies a pristine wilderness. There’s also this sense that it is alien. That’s what first captivated me. But now I think we look at the planet a little bit upside down. We call it the blue planet yet actually the blue bit is only the surface layer. By area, it is a dark, deep-ocean planet. And the deep ocean is certainly not pristine: our everyday lives have been affecting it for a long time. When our great-great-grandparents travelled on steamships, the remains of the burnt coal from the engines were shovelled over the side. On well-travelled routes, that has shifted the seabed from a soft mud to cobbles, which in turn has changed the marine life in those areas. Back then, people had no notion this was happening.
Now everyone is worried about plastics. What effect are they having in the deep ocean?
We simply don’t know enough. Imagine life as a sea cucumber deep in the ocean, on a fine-mud abyssal plain. These animals plough their way through the mud’s surface, swallowing it, extracting whatever nutrients they can from the organic material that has fallen from above. Today, a proportion of that material is microplastics, which have no nutritional content. Even if this plastic weren’t toxic, ingesting it means the sea cucumbers have less energy for reproduction. What does that mean for their population in the long term? The knock-on effects are uncertain, and that’s just one impact of many we have started to appreciate.
Why is it so important to explore the deep ocean?
To enable us to make informed choices. One choice we face relates to deep-sea mining. Some mineral resources are in increasingly short supply on land. For example, wind turbines require excellent magnets, which need neodymium. Manganese nodules on the abyssal plains of the eastern Pacific are a particularly rich source. Then there’s cobalt, which we need for electric-car batteries.
Proponents of deep-sea mining argue that the direct impacts on human populations from this kind of mining are fewer, so in many ways this is a less deleterious form of mining. My view is that the deep oceans should be off limits until we understand more about them. We tend to rush in to exploit resources, realise we are having a bad impact, then bring in regulation. Here we have an opportunity to do it the other way around.
What’s your outlook on the mining situation?
I’d call myself an optimistic futurist. If we are smart enough to get down there in the deep ocean to explore it, then we are smart enough to come up with alternatives to taking those resources.
This article appeared in print under the headline “Blue planet? It’s a dark, deep-ocean world”
