In The Brilliant Abyss, Helen Scales warns against the desecration of the sub-sea realm

Bloomsbury, £16.99

Review by Vicky Allan

The North Sea washes up against the margins of my city. Whenever I wade into it, as I have done regularly over the years in which I have called myself a wild swimmer, I appreciate that sense of being on the edge of something vast, a sea that connects with an ocean and which is part of a body of water that covers the planet.

I am a lover of the sea’s strangeness. I usually wear goggles so I can take in the dreamscape beneath, even if it’s mostly little more than seaweed, rock and molluscs. One of its allures is its unfamiliarity – the alien nature of the life that inhabits it.

But I’m aware that these shores are just the very edge of something still more marvellous – the wonder of the deep ocean, of what are called the twilight zone, the midnight zone, the hadal zone. It’s this realm that marine biologist Helen Scales conjures in The Brilliant Abyss, a book that first offers delight at the life of what she calls “the deep”, then fiercely argues for its protection.

One of the joys of Scales’s writing is the way she not only tells stories of life cycles and ecosystems, but also portrays the beauties of underwater organisms. At times I wanted to look up photographs of fish described, at others just to revel in the images she prompted. “This,” she writes, “is the domain of jelly creatures so fragile they would fall straight through your fingers if you tried to pick one up, and yet they remain unperturbed by pressure so extreme it would squash your body’s cells and molecules lethally out of shape.” Here are “glistening spheres with rainbows flickering across them and elaborate glass chandeliers complete with glittering lights”.

This is a world, as yet, relatively uncharted. It’s also one that has held our imagination for millennia, spawning tales of monsters like the Gaelic sea serpent Ceirean, so large that it “fed seven whales”, or the Icelandic sea monster Hatgufa, which disguises itself as islands.

The real-life creatures Scales describes seem more marvellous again – for instance, the zombie bone-eating worm, which feeds on the dead carcasses of whales that have sunk to the bottom of the ocean and which is female but contains its own dwarf male harem. Or the Yeti crab, with pincers covered with blonde fur, thriving around hydrothermal vents, living off food produced by chemosynthetic bacteria it hosts.

A vital element in the ecosystems of the deep is "marine snow", a blizzard of dead organisms, phytoplankton, zooplankton and biological debris that floats downwards and is a vital part of a carbon sink. As Scales puts it: “Phytoplankton harness the sun’s energy, using it to convert carbon dioxide into carbohydrates, some of which gets consumed and is breathed back out as carbon dioxide, some stays in the ocean as uneaten phytoplankton die and sink as marine snow.”

The Brilliant Abyss, however, is not just a story of wonder, it’s also one of how we have exploited seas, of fishing fleets “pushing deeper, year after year, depleting populations of typically slow-growing, long-lived fish”. Scales describes the lives of sperm whales, one of the deepest diving species of Cetaceans, organisms which make regular plunges to hunt in the twilight and midnight zones.

Sperm whales, she notes, are connected to phytoplankton and the carbon sink. After feeding in the depths, they come back up and defecate, leaving an iron-rich slick in the shallows, which fertilizes the phytoplankton. “Before industrial whaling,” writes Scales, “abundant Antarctic sperm whales fertilised enough phytoplankton to remove more than two-million tons of carbon from the atmosphere every year, equivalent to the annual carbon emissions from the city of Washington DC.”

These same whales, of course, were also hunted by whalers for spermaceti, a substance contained in their echolocation chambers, which was then used for candles, and “lit the streets of Europe and North America”. In the course of the 20th century, 761,523 sperm whales were killed. As Scales points out: “In the 20th century humans killed more than twice the number of sperm whales that remain alive today.”

Other sea animals tragically exploited include the orange roughy, a fish that can live for 250 years but which was overfished in the 1970s and 1980s in trawling sprees so big that one giant net pulled out fifty – an animal weight equal to 25 rhinoceroses. Scales quotes Matthew Gianni, a former deep-sea fisherman turned campaigner who recalls once seeing them piled high on supermarket counters. “I remember thinking what a waste, what a sad thing to do ... Here were fish that were 100 years old or more from some of the deepest, remotest, most biologically diverse areas in the ocean, being sold by the pound for not much more than the price of farm-raised tilapia.”

While fishing for deep sea species like orange roughy, industrial trawlers also managed to destroy undersea mountains around which they fed, pulling up, with the fish, broken coral remnants. “Like the felling of ancient terrestrial forests that take centuries to mature, the destruction of deep-water corals leaves the planet in a diminished state,” writes Scales.

She argues vehemently against the rush towards a new kind of exploitation of the deep – the mining of the seabed for rare metals to use in the batteries of the renewables revolution. The seabed would be disrupted, toxins stirred up that would contaminate fisheries. Such a seabed rush, she writes, “risks triggering a global addiction to virgin metals that would be very hard to give up, and which could be avoided in the first place”.

The entire deep-sea realm should be ruled off-limits, Scales argues. “No mining, no fishing, no drilling for oil and gas, from the top of the twilight zone to the deepest trenches, no extraction of any kind.”

I found myself echoing her rage. That feeling has been fuelled since by watching the Netflix documentary Seaspiracy. Time spent in the sea has led me to believe that we humans are not very good at fighting for things we can’t see. What goes on underneath the surface of the ocean is not visible and too often ignored. Whether it’s Scotland's inshore seabed, wrecked in so many areas by trawling and dredging, or the abyssal bed, we can’t afford to turn a blind eye. Just because all we see is crashing waves or reflected sky, doesn’t mean we shouldn’t protect what’s underneath.