The Brilliant Abyss True Tales of Exploring the Deep Sea, Discovering Hidden Life and Selling the Seabed

Marine biologist Helen Scales returns for her third book with popular science imprint Bloomsbury Sigma. After shells and fish, she now drags the reader down into the darkest depths of the deep sea. Both a beautifully written exploration of the ocean's otherworldly wonders and a searing exposé of the many threats they face, The Brilliant Abyss is Scales's most strident book to date.

Sir David Attenborough has probably said it best: "No one will protect what they do not care about; and no one will care about what they have never experienced". Both Scales and the publisher have taken that message to heart and the book is neatly designed. As with her previous book, illustrator Aaron John Gregory is involved again, this time providing two beautiful end plates and an eye-catching cover, while the colour plate section contains some outstanding photos. But at the heart of The Brilliant Abyss is Scales's captivating writing.

First, consider the landscape. As she explains, the seabed, shaped by plate tectonics, is far from a featureless bathtub. Spreading centres create colossal mid-ocean ridges while subduction zones form deep-sea trenches of terrifying depths. The abyssal plain in between is studded with underwater volcanoes that form seamounts of great import to marine life. Wherever magma approaches the surface, percolating seawater becomes superheated, rising back to the surface laden with dissolved minerals and metals. They form hydrothermal vents: "the deep-sea equivalent of hot springs and geysers on land" (p. 97) that are home to unique fauna. Woven throughout is a history of scientific exploration, from the first oceanographic expeditions to today's robotic submersibles, and from pioneering deep-sea explorers to today's trench-diving billionaires.

Otherworldly as the landscape is, the real stars of this realm are its fauna. Scales's knowledge and love of marine biology shine through here, as she populates the pages with a bewildering cast of creatures. Notable examples of bizarre deep-sea fishes are included, but she gives you so much more. Whale carcasses or whale falls become complete ecosystems, home to bone-eating Osedax worms with unusual sex lives. Large gelatinous members of the drifting plankton, such as colonial siphonophores and giant larvaceans, form previously underappreciated links in the food web. Hydrothermal vents are crowded with worms and furry Yeti crabs that domesticate symbiotic bacteria capable of chemosynthesis, the "dark alternative to photosynthesis" (p. 104). Meanwhile, one species of snail makes its shell out of iron! And then there are the corals. No, not the familiar tropical corals who "hog not only the sunlight but the limelight" (p. 129); the lesser-known cold-water corals that occur at great depths and grow even slower.

And if the intrinsic value of biodiversity does not sway you, Scales is no stranger to discussing the deep's instrumental values. The capacity of seawater to absorb heat and carbon dioxide. The role of global oceanic currents in regulating our climate. Or the carbon pump provided by marine snow; the constant rain of dead plankton, fish poop, and other organic debris that descends into the depths. And what of the quest for new classes of biological compounds could form the pharmaceutical drugs and antibiotics of the future?

Two-thirds through the book Scales switches gears. Now that she has your attention, it is time to highlight the many dangers the deep faces. Deep-sea fishing targets long-lived, slow-growing species such as orange roughy. Vulnerable seamounts with millennia-old corals are destroyed by trawlers in a matter of hours. Meanwhile, the promise of food for everyone is not being met. Vast catch volumes are being turned into fish meal for aquaculture and pet food, or questionable nutraceuticals such as omega-3-oil supplements. And where Daniel Pauly already gave me reason to be suspicious of the Marine Stewardship Council, Scales lays bare their dubious raison d'être: funded by royalties from sales of their eco-labelled fish, there is an imperative to keep certifying fisheries. She calls their scandalous certification of the "recovering" orange roughy population a "case of a dead cat bouncing, with a green-washed eco-label tied to its collar" (p. 204).

Scales made me shudder with her stories of pollution, especially the persistent legacy of the large-scale dumping of chemical weapons. But the topic that concerns her most is the looming spectre of deep-sea mining. Though much is still on the drawing boards, mining licenses are being issued and exploratory missions are taking place. What for? The minerals and metals contained in seamounts, hydrothermal vents, and the polymetallic nodules littering the seabed, which take millions of years to form. As with fishing, "the slow pace of the deep is out of step with the timescale of impatient human demands" (p. 205). Here too, the position of the body that oversees protection of the seabed, the International Seabed Authority, is incredibly compromised. Next to issuing mining permits they unbelievably have already assigned areas to be exploited by their own mining company!

Scales's focus on deep-sea mining is urgently needed. Scientists have been sounding alarm bells in the peer-reviewed literature regarding its impact, but this topic is still mostly hidden from the public at large. Her descriptions of the destructive practices and the size of the machines involved are chilling. To think that this will result in anything but the rapacious plundering of ecosystems we have seen on land seems highly unlikely in her eyes. Meanwhile, the mining PR-machine is already running at full tilt, and Scales deftly disarms their arguments as to why deep-sea mining is necessary. She agrees that the shift to renewable energy requires infrastructure that needs tremendous amounts of diverse metals. However, as a detour into the design of wind turbines shows, predicting which ones will be needed is difficult. And whether the seabed is the best place to get them is highly questionable.

Scales tackles many of the same topics that Alex Rogers covered in The Deep. Her tone is more strident but no less knowledgeable and, as opposed to The Deep, her book does include endnotes with references. I recommend them both highly. Meanwhile, her call "to declare the entire realm off limits [to] extraction of any kind" (p. 286) meshes seamlessly with Deborah Rowan Wright's bold vision laid out in Future Sea.

Whether you have enjoyed her previous books or are new to her brand of writing about marine biology, I urge you to read this book. Next to an unforgettable trip, she provides a rousing rallying cry for the preservation of the deep sea. The Brilliant Abyss is, true to its title, brilliant.