There is an abundance of weird and wonderful life in the depths of the sea – and The Brilliant Abyss by Helen Scales is an excellent introduction to it

Life



10 March 2021

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A deep-red jellyfish in the medusa stage, living in the Arctic Ocean

NOAA

The Brilliant Abyss

Helen Scales

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Bloomsbury (Buy from Amazon*)

AT THE bottom of the Mariana trench, the water is chillingly cold and dark, with a pressure so high it can dissolve shells and exoskeletons. It is the ocean’s deepest point, lying almost 11 kilometres beneath the surface, and it is home to a remarkable crustacean.

This shrimp-like creature is called an amphipod and it has an ingenious adaptation to survive the conditions: it uses metallic compounds from mud to make itself a coat that prevents its exoskeleton from dissolving. With this protection, the scavenger can scour the trench for the food that builds up there, funnelled to the bottom by underwater avalanches.

In The Brilliant Abyss, marine biologist Helen Scales describes amphipods and the many other remarkable creatures that live in the deep sea. Weaving together the latest discoveries with well-known examples, she details the many fascinating adaptations that life has evolved to survive in a world unlike anything at Earth’s surface.

There are vampire squid, for example, which hang around in the cold water waiting not for blood-filled prey, but to make edible snowballs out of the flurries of detritus that fall from the ocean surface that are known as marine snow. Then there are corals that started growing more than 4000 years ago and female octopuses that spend five years without food so they can brood a single clutch of eggs. And then there are the inconspicuous ultra-black fish that reflect hardly any light so that they blend into the background.

“There are female octopuses that spend five years without food so they can brood a single clutch of eggs”

At gushing hydrothermal vents and the gentler cold seeps are clusters of Yeti crabs, which use their furry arms to farm bacteria for food. Their bacterial crops are chemosynthetic, meaning they can use the methane and hydrogen sulphide in the bubbling water as an energy source, much like plants do with sunlight.

After detailing this diverse underworld, the book takes a darker turn to explore the threats these creatures face from us. Deep-sea fishing is the most well-known example. It is “an industry that yields relatively trivial economic benefits but a fearsome capacity to vandalise our living planet”, writes Scales. An increasing threat lies in projects to mine the seabed to satisfy humanity’s growing demand for metals, particularly to use in the green tech needed for a low-carbon future. The choice is portrayed as one of green or blue, writes Scales, “the greening of global economies pitted against the health and integrity of the blue oceans”. But she says there is a third path: recycling the metals we have already dug up.

These problems are out of sight and out of mind to many. Scales lists why we should care about them, including the deep’s key role in feeding the surface fisheries that many people rely on for food, as well as its mitigating impact on climate change. “In total, a third of humanity’s carbon emissions make their way into the ocean,” she writes, “saving the Earth from an unthinkably swift and catastrophic version of the climate crisis.” While this is pragmatic, I do wish we didn’t have to think up positive ways to exploit an environment in order to convince people that it is worth protecting.

The Brilliant Abyss is an enjoyable and accessible introduction to the deep sea, told with a passion that I found infectious. The stories of life’s struggle for survival beneath the waves are compelling and Scales is particularly evocative when describing hydrothermal vents. I would have liked to read more about bioluminescence and the creatures that use it to dazzle predators and prey alike, however, and the book can become lost in detail when it leaves the deep, such as a pages-long digression about batteries.

Overall, though, Scales brings to life this important part of our planet. What happens there is something we should all be concerned about. As Scales puts it: “The deep, quite simply, makes this planet habitable.”

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