 | The Underworld: Journeys to the Depths of the Ocean is part travelog, part history lesson, and overflowing with loving fascination for our oceans. The author, Susan Casey, writes: "In the deep, there are creatures that breathe iron and creatures with glass skeletons and creatures that communicate through their skin. … They might have two mouths, or three hearts …Some have see-through heads. Even the most ethereal can handle pressures that would crush a Mack truck.” |
Earth’s biosphere is 95% deep ocean, yet we know surprisingly little about this watery aspect of our planet. For every dollar spent on ocean exploration, “NASA gets a hundred and fifty. We lavish billions on the prospect of colonizing Mars, a barren dust ball.”
She attributes this imbalance to “our terrestrial bias, the mistaken belief that everything important happens above ground, because that’s where we live.”
We are creatures dependent on light, “But in fact, most of the biosphere exists in the dark.”
She attributes this imbalance to “our terrestrial bias, the mistaken belief that everything important happens above ground, because that’s where we live.”
We are creatures dependent on light, “But in fact, most of the biosphere exists in the dark.”
Twilight Zone: 600-3300 feet deep
 Phosphorescent jellyfish | “The twilight zone is an eat-or-be-eaten kind of place, lit by the signal flares of bioluminescence: the come-hither lures glowing in front of gaping fanged maws, the pulse and flash of slinky bodies, the flickering of neon-colored photophores that line the bellies of a quadrillion fish.” "This gelatinous galaxy also includes the arch predators called siphonophores--glimmering chains of cloned cells that zap prey in a stinging net and can grow up to 150 feet long" "The twilight zone is unrivaled in its profusion of zany life-fromes. See-through octopuses, swimming worms with corkscrew tentacles, and eel with a mouth like a pelican, the three-inch long firefly squid...a jellyfish with 24 eyes" "A dragonfish’s teeth are stronger than the great white shark's and reinforced with nanocrystals that don't reflect light, making its pit trap jaws invisible to prey. " |
| The barreleye fish: "Its tubular green eyes are sealed inside its transparent head and can rotate directly upward, enabling the barreleye to gaze out of the top of its own noggin. |  Barreleye fish |
"Scientists think maybe half the twilight zone’s population migrates each night--trillions of fish, crustaceans, and others rising and falling in unison, as though the ocean itself were breathing.
"By eating plankton near the surface (inhale) and then swimming back down and excreting it (exhale), the animals are shuttling carbon from the atmosphere into the depths, where it remains sequestered for centuries and, in some cases, millenia. These tiny beasts sink …an estimated 4.4 billion tons of carbon each year, the equivalent of America’s total annual emissions."
"By eating plankton near the surface (inhale) and then swimming back down and excreting it (exhale), the animals are shuttling carbon from the atmosphere into the depths, where it remains sequestered for centuries and, in some cases, millenia. These tiny beasts sink …an estimated 4.4 billion tons of carbon each year, the equivalent of America’s total annual emissions."
Hadal Zone: 20,000 to 36,000 feet deep
 Balck smoker vent | At the very deepest hadal zone, life is dependent on ingesting chemicals put off by hydrothermal vents (black smokers) that sprout where the earth’s mantle splits: “Mantle rock is solid, but it behaves like angry Silly Putty. …When dragged from its deep womb and exposed to seawater it reacts, chemically [and] throws off heat, hydrogen, and methane in a kind of planetary hissy fit.” An equal amount of mantle is being reabsorbed through subduction: “It’s an elegant system, with new crust arriving and old crust deepening in perfect equilibrium as the planet recycles itself.” |
“Microbes that can reside way down in the pores and fissures of the ocean crust--in extreme temperatures, under annihilating pressures, and subsisting on toxic chemicals--are the champions of adaptation. ...these creatures relied on chemosynthesis: energy coming from the earth’s interior, produced by chemical reactions between fluids and rocks. The microbes were eating hydrogen sulfide--a poison to creatures on land--and oxidizing the food to vent animals, many of which hosted the microbes inside their bodies in a symbiotic relationship.”
 Tubeworms | “There were tubeworms with feathery oxblood plumes and violet-white tubes kinked like antique plumbing, and palm worms that resembled tiny, burgundy-colored palm trees, and hardy sulfide worms that secrete their own protective metal armor." |  Giant tubeworm |
"The red in their plumes is hemoglobin-rich blood (adapted to transport hydrogen sulfide as well as oxygen). They have no eyes, no mouth, no gut, no anus…But the worms’ biology is suited for their environment. They feed by absorbing the bacteria through their skin, and housing them in a special organ called a trophosome. As the vent fluid washes over them, they breathe it in through their plumes--which act as gills--and then the bacteria take over, ingesting the chemicals, converting them to energy, and sharing the meal with their hosts.”
Human Impact:
 Trash clogging ocean floor | “Along with microplastics and synthetic fibers, in recent years scientists have found that the [deepest] hadal trenches are thick with every toxin we’ve ever unleashed: persistent organic pollutants like PCBs (industrial poisons), PBDEs (flame retardants), DDT (pesticide), phthalates (plasticizing chemicals), along with lead, mercury, pharmaceutical waste, and radioactive carbon from nuclear bombs. From the ocean’s surface to its deepest sediments, all the way up the marine food chain, we have left our mark." |
What to do? Minimize consuming plastics and other synthetics; recycle; purchase and use biodegradable products and packaging (paper, cotton, wool, wood). What we buy influences what is manufactured.
As the author writes: “the ocean simmers with magic, and the deeper you go, the more magical it becomes.” Help keep the magic alive!
As the author writes: “the ocean simmers with magic, and the deeper you go, the more magical it becomes.” Help keep the magic alive!
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