Did life begin in the deep sea?
Life on Earth began about four billion years ago. Where and how those simple cells first sparked into life remain mysteries, but evidence is stacking up that they could have first emerged in the deep ocean.
How many undiscovered creatures live in the deep sea?
One thing is clear: scientists aren’t going to run out of new, deep-sea species to find any time soon. In a recent three-year study in the Pacific Ocean, remotely operated vehicles photographed nearly 350,000 animals: fish, octopuses, corals, anemones, shrimp, squid, sponges, and sculpted, living mud balls called xenophyophores… the list goes on. Only one in five were known species. Not all the images were clear enough to identify, but most were organisms nobody had seen before.
Will we ever build a deep-sea base?
Technically speaking, there is nowhere in the abyss that’s entirely off limits to humans. A growing roll call of brave and curious people have paid brief visits to the ocean’s greatest depths. Earlier this year, Nicole became the first Pacific Islander, the third woman and the youngest person to descend into the Challenger Deep in the Mariana Trench, the ocean’s deepest point at close to 11 kilometres down.
But going down and staying down is a different undertaking. The people who have so far spent the longest time deep underwater are commercial divers who carry out construction work on oil and gas installations. They spend weeks inside pressurised capsules on ships and oil rigs, commuting each day inside a diving bell to their work site 100 metres or more below. Their bodies stay saturated with diving gases the entire time, until they are slowly decompressed at the end of each mission.
Scientists have also adopted saturation diving as a means of spending more time at greater depths. A pioneer of this was French underwater filmmaker, Jacques-Yves Cousteau, who in the 1960s built a starfish-shaped underwater base in the Red Sea called Conshelf II. His grandson, Fabien Cousteau, is now planning a next generation, deep-sea facility called Proteus.
“In order for us to understand something as complex, something as mysterious, something as foreign as the ocean world, one has to spend a lot of time down there,” Cousteau said, when we spoke about Proteus on the Catch Our Drift podcast.
Dubbed the first International Space Station for the ocean, Proteus will be a larger and more adaptable version of previous underwater habitats including Aquarius in Florida – the only one still in operation and where in 2014 Cousteau spent a record-breaking 31 days living.
Will the climate crisis change the deep sea?
Climate change is already reaching down into the deep ocean. A 2020 study confirmed the average global temperature between the surface and 2,000 metres has been rising year on year. The increase may seem small — in 2019, it was 0.075°C above the average between 1981 and 2010 — but due to the volume of water, the heat absorbed is equivalent to the energy of 3.6 billion atomic bombs exploding.
And there are greater changes on the way. By the end of the century, it’s predicted temperatures in the twilight and midnight zones, down to 1,000 and 4,000metres respectively, will rise to 8°C. This will come as a hot shock for deep-sea organisms that are adapted to around 4°C.
Other climate impacts will accompany the rising temperatures. Ocean acidification is expected to hit hardest between 200 and 3,000 metres down, where deep-sea corals will find it increasingly difficult to make their exoskeletons. Warming seawater will lose its ability to hold oxygen. In the northeast Pacific, off Vancouver Island, oxygen levels down to 3,000 metres have already declined by 15 per cent over the last 60 years.
What does the seabed look like?
It’s been said many times that we know more about the surface of the Moon than the bottom of the sea. This is true, at least in terms of the maps we have, but it’s a fact that’s gradually changing.
The entire surface of the Moon has been mapped to a resolution of seven metres. Compare that to the best complete maps of the seabed, which are created using satellites that measure bulges in the sea surface and only show features that are at least 5km across.
It’s worth bearing in mind that the area of the Moon is about 10 times smaller than the Earth’s seabed, and with no ocean getting in the way it’s a good deal easier to see what’s going on up there. Even so, scientists and engineers are finding new, better ways of mapping the bottom of the sea.
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