- 1. Antarctica.
- 2. The coldest, the harshest,
and the most remote continent on Earth.
- 3. No human being has ever descended
into the depths that surround it...
- 4. until now.
- 5. The deep ocean is as
challenging to explore as space.
- 6. We know more about the surface of Mars
- 7. than we do about
the deepest parts of our seas.
- 8. Now we can dive
these uncharted depths,
- 9. to discover what secrets lie beneath.
- 10. Sinking down beside
the submerged wall of an iceberg,
- 11. we enter an unforgiving world.
- 12. These waters
are the coldest on Earth.
- 13. As we descend into the deep,
- 14. the pressure increases relentlessly.
- 15. And the light from above
all but disappears.
- 16. Yet, incredibly...
- 17. there is life here.
- 18. We might have expected
- 19. that deep beneath
the surface of the Polar seas,
- 20. the waters would be truly barren.
- 21. But, in fact, we find life here
in unimaginable abundance.
- 22. Nor is such great abundance
confined to Antarctic waters.
- 23. Currents carry this richness
- 24. into the depths of almost
every ocean around the world.
- 25. Astonishingly, in the deep sea,
- 26. there is more life
than anywhere else on Earth.
- 27. The sunlight fades,
- 28. and the seas darken.
- 29. Here, in the Pacific, 200 metres down,
- 30. we enter an alien world.
- 31. The Twilight Zone,
- 32. a sea of eternal gloom.
- 33. There are strange creatures here.
- 34. A pyrosome.
- 35. A tube of jelly two metres long
that dwarfs a visitor from above,
- 36. an oceanic whitetip shark.
- 37. Only a tiny amount of light
filters down this far.
- 38. Survival here means making the most
of every last glimmer.
- 39. A swordfish.
- 40. Its eyes are as big as tennis balls
to help it see in the perpetual dusk.
- 41. A squid, but this is one
that lives only here.
- 42. Its right eye
looks permanently downwards.
- 43. But its left eye is much bigger
and trained upwards
- 44. to detect the silhouettes of prey
swimming nearer the surface.
- 45. No wonder it's nicknamed
the "cock-eyed squid".
- 46. And even stranger,
- 47. this is barreleye,
- 48. a fish with a transparent head,
- 49. filled with jelly,
- 50. so that it can look up
through its skull.
- 51. We now know that
the Twilight Zone is a refuge
- 52. for an incredible 90%
of all fish in the ocean.
- 53. Only at night,
do vast shoals of lanternfish
- 54. migrate to the surface
to feed on tiny plankton.
- 55. By day, they retreat back down here.
- 56. Humboldt squid.
- 57. Two metres long
and 50 kilos in weight.
- 58. Like most squid,
they're voracious hunters.
- 59. There are hundreds of them.
- 60. They found a shoal of lanternfish
- 61. hiding 800 metres down,
off the coast of South America.
- 62. Their tentacles are armed
with powerful suckers
- 63. with which they grab their prey.
- 64. And when there are
no more lanternfish to be found,
- 65. they turn on each other.
- 66. This squid has caught
a smaller one in its tentacles.
- 67. To hide its capture from the rest,
- 68. it releases a smokescreen of black ink.
- 69. But then, an even
bigger one challenges it
- 70. and steals its catch.
- 71. The Twilight Zone
- 72. is the Humboldt squid's
favourite hunting ground.
- 73. They seldom go deeper
- 74. into the world
of perpetual blackness below.
- 75. The Midnight Zone.
- 76. Two-thirds of
a mile from the surface,
- 77. beyond the reach of the sun.
- 78. A giant black void
- 79. larger than all the rest
of the world's habitat's combined.
- 80. There's life here,
- 81. but not as we know it.
- 82. Alien-like creatures
- 83. produce dazzling displays of light.
- 84. Nearly all animals
need to attract mates
- 85. and repel predators.
- 86. This language of light
is so widespread here,
- 87. that these signals are probably
the commonest form of communication
- 88. on the entire planet.
- 89. And yet,
we still know little about them.
- 90. Hunters illuminate themselves,
- 91. and by doing so
- 92. attract inquisitive prey.
- 93. This is fangtooth.
- 94. It has the largest teeth
for its size of any fish.
- 95. There are pressure sensors
all over its head and body
- 96. which can detect anything
moving in the surrounding water.
- 97. It's the Midnight Zone's
most voracious fish.
- 98. But prey use light as a distraction.
- 99. A decoy of luminous ink.
- 100. Down here, in this blackness,
- 101. creatures live beyond
the normal rules of time.
- 102. Siphonophores are virtually eternal.
- 103. They repeatedly clone themselves,
- 104. some eventually growing
longer than a blue whale.
- 105. Down here, it snows.
- 106. Continuous clouds of organic debris
- 107. drift slowly down from above.
- 108. This is food,
- 109. and a whole variety
of filter feeders depend on it.
- 110. Jellyfish.
- 111. And delicate sea cucumbers.
- 112. The 1% of marine snow they miss
- 113. eventually settles on the sea floor.
- 114. Over millions of years,
- 115. it forms a layer of mud
up to a mile thick.
- 116. It's an empty plain
- 117. that covers half
the surface of our planet.
- 118. The deep seabed may,
at first, appear lifeless,
- 119. but it's home to a unique
cast of mud dwellers.
- 120. The sea toad.
- 121. It is an ambush predator
with an enormous mouth
- 122. and infinite patience.
- 123. This fish has been
living for so long here
- 124. that its fins have changed
into something more useful.
- 125. Feet.
- 126. They help it shuffle about
on the sea floor.
- 127. The flapjack octopus.
- 128. It hovers just above
the surface of the mud
- 129. as it delicately sifts through it
searching for worms.
- 130. But it can jet away
at the first sign of danger.
- 131. A sixgill shark,
as big as a great white.
- 132. It may not have eaten
for an entire year.
- 133. It patrols the mud plains
- 134. using a minimum amount of energy.
- 135. High above,
- 136. the carcass of a huge sperm whale
- 137. is slowly decaying.
- 138. This will be a bonanza
for the creatures of the deep.
- 139. Food.
- 140. Thirty tonnes of it.
- 141. Finally it settles on the ocean floor
- 142. and its presence is soon detected.
- 143. Sixgills sharks
- 144. have an exceptionally
acute sense of smell.
- 145. just 25 minutes
after the whale's carcass arrives,
- 146. a sixgill finds it.
- 147. Each bite releases
blood into the current.
- 148. The news that food
is here spreads quickly.
- 149. Two more ravenous sixgills arrive.
- 150. Within 12 hours,
there are seven enormous sharks
- 151. jostling with one another
- 152. as they compete to tear off mouthfuls.
- 153. No one is prepared to back off.
- 154. Twenty-four hours later,
- 155. and a third of the carcass has gone.
- 156. The first arrival has gorged
- 157. until it's completely full.
- 158. This single meal
- 159. may be enough to sustain it
for a whole year.
- 160. Now, the clean up team arrives.
- 161. Spider crabs carrying coral
in their hind legs,
- 162. presumably as makeshift body armour.
- 163. There are rock crabs here too.
- 164. They probably detected the carcass
almost as soon as the sharks,
- 165. but they can't move as fast.
- 166. A month on,
and over 30 species of scavenger
- 167. are clearing away
the last edible fragments.
- 168. But now, the scavengers
are attracting their own predators.
- 169. Scabbardfish, habitually
- 170. are picking them off one by one.
- 171. Some of the whale's teeth
have been dislodged
- 172. as the skeleton starts to fall apart.
- 173. Four months later,
there is nothing left but a few bones.
- 174. But even they are food
- 175. for something.
- 176. Zombie worms.
- 177. They tunnel into the bones
by injecting acid
- 178. and so reach the tiny amounts of fat
that still remain there.
- 179. It may take decades,
- 180. but eventually,
the last of the bones will crumble,
- 181. and the whole 50-tonne carcass
will have been recycled.
- 182. A whale fall is a temporary oasis
- 183. in the desert of the sea floor.
- 184. But there are permanent oases here too.
- 185. Rocks projecting above the mud
- 186. provide anchorage for deep sea corals.
- 187. As far down
as three and a half miles,
- 188. there are more species of coral
in the deep
- 189. than on shallow tropical reefs.
- 190. Without sunlight,
they rely solely on food
- 191. drifting in the current.
- 192. And they grow
- 193. just a hair's breadth a year.
- 194. But some of them
can live for 4,000 years.
- 195. They, like their
shallow water relatives,
- 196. provide homes for all kinds
of other creatures.
- 197. Growing among the corals,
- 198. is one of the most beautiful of sponges.
- 199. This is Venus' flower basket.
- 200. These sponges have lodgers.
- 201. Shrimps.
- 202. There are plenty
of predators on the reef
- 203. so the shrimps are fortunate.
- 204. Both this male and female,
- 205. were swept into this sponge
when they were tiny larvae,
- 206. along with the minute particles of food
- 207. on which the sponge feeds.
- 208. They found each other
and have been here ever since.
- 209. Now, they're full-grown
- 210. and the female is carrying eggs.
- 211. Once hatched, the larvae will swim
out through the sponge's walls.
- 212. But the shrimps will never leave.
- 213. They can't.
- 214. They're now far too big
to go out the way they came in.
- 215. And, no doubt,
they will live longer here
- 216. than they would if they were
wandering about on the reef unprotected.
- 217. But how one
of the simplest of all animals,
- 218. a sponge, is able to build
such a complex structure
- 219. to the great benefit of the shrimps
- 220. is a mystery.
- 221. And, surely, a marvel.
- 222. But today,
- 223. their timeless world
is being reduced to rubble.
- 224. As over-fishing empties
the surface waters of the seas,
- 225. trawlers have started
to ransack the deep.
- 226. Now, countless numbers of the reefs
- 227. that have flourished here for millennia
- 228. lie in ruins.
- 229. Over time,
- 230. organic matter on the sea floor
- 231. producing methane.
- 232. In the Gulf of Mexico,
- 233. these eruptions also release
a super salty liquid.
- 234. Brine.
- 235. Five times heavier than sea water,
- 236. it accumulates in great pools
on the sea floor.
- 237. It's difficult to make sense
of the sight.
- 238. A lake of concentrated salt water,
- 239. fifteen metres deep,
- 240. at the bottom of the sea.
- 241. Around its margin,
perhaps even more strangely,
- 242. there is a profusion of life.
- 243. Giant mussels that can live
or grow for a century or more,
- 244. pack tightly together,
- 245. dwarfing the shrimps and squat lobsters
that feed around them.
- 246. Cutthroat eels, scavengers,
- 247. come to the shores of the brine lake
- 248. in search of something edible.
- 249. Some even venture into the brine.
- 250. Spending too long in it
can send an eel into toxic shock.
- 251. It' only hope
is to rise above it.
- 252. It manages to escape.
- 253. Others are not so lucky.
- 254. The brine embalms their bodies,
- 255. and the casualties of decades
accumulate around the margins.
- 256. But parts of the deep
are even more hostile.
- 257. In places,
- 258. gigantic cracks stretch for many miles
across the ocean floor.
- 259. Canyons that plunge
towards the centre of the earth.
- 260. Scans from survey vessels
- 261. make it possible to graphically
reconstruct an image
- 262. of this vast submarine landscape.
- 263. The deepest of all,
at almost seven miles,
- 264. is the Mariana Trench
in the Pacific Ocean.
- 265. Even Mount Everest
could disappear inside it.
- 266. Down here, in these deep ravines,
- 267. it was once thought that
nothing whatever could possibly survive.
- 268. But there is life even here.
- 269. A kind of sea slug.
- 270. A so-called sea pig.
- 271. They, and other simple creatures,
- 272. manage to survive on the minuscule
amount of food that drifts down here.
- 273. Like this starfish,
- 274. they can withstand pressure
equivalent of 50 jumbo jets
- 275. stacked on top of one another.
- 276. A remote camera probe
- 277. reveals the most
extraordinary discovery of all.
- 278. The ethereal snailfish.
- 279. At five miles down,
- 280. this is the deepest living fish
so far discovered.
- 281. No one imagined
- 282. than an animal as complex as a fish
- 283. could exist in such extreme pressures.
- 284. From the greatest depths
- 285. to the uppermost limit
of the Twilight Zone,
- 286. it seems that there is
nowhere in the deep sea
- 287. where life of some kind can't survive.
- 288. And we now think
- 289. that the deep sea may well be
where life on Earth began.
- 290. Here,
- 291. in a world hidden within the greatest
geological feature on Earth,
- 292. running right down the middle
of the world's oceans,
- 293. an underwater mountain range
- 294. spanning the entire globe.
- 295. The mid-ocean ridge.
- 296. In the South Pacific,
- 297. the ocean floor is being torn apart.
- 298. Over three quarters
of the planet's volcanic activity
- 299. occurs in the deep.
- 300. Almost all of it along
the mid-ocean ridge.
- 301. But from this titanic violence
- 302. come great riches.
- 303. Gases and scalding water
gush up through the crevices.
- 304. Minerals condensing from these jets
- 305. build up great chimneys.
- 306. Hydrothermal vents.
- 307. This one, 30 metres tall,
- 308. has been named "Godzilla
- 309. Astonishingly, we now know
- 310. that they hold as much life
as tropical rainforests.
- 311. In places, half a million
- 312. are crammed into a single square metre.
- 313. They depend entirely
for their food on bacteria.
- 314. And they feed on chemicals
- 315. dissolved in the searingly hot fluid.
- 316. Crabs consume the bacterial mats
- 317. that coat their shells.
- 318. Others maintain
- 319. actually within their bodies.
- 320. Shrimps carry such cultures
in their mouth parts.
- 321. But that is a strategy
fraught with danger.
- 322. To provide sustenance
for these microbes,
- 323. the shrimps must dash
into the hot vents,
- 324. and that risks being boiled alive.
- 325. In the last decade,
- 326. the number of hydrothermal vents
discovered has doubled.
- 327. Every one has its own unique
character and community.
- 328. But, perhaps, the most important
one of all is in the Atlantic.
- 329. It has been named "The Lost City".
- 330. Within its 60-metre towers,
- 331. something truly extraordinary
is taking place.
- 332. Under extremes
of pressure and temperature,
- 333. hydrocarbons,
- 334. the molecules that are the basic
component of all living things,
- 335. are being created spontaneously.
- 336. Indeed, many scientists now believe
- 337. that life on Earth
may have begun around a vent like this
- 338. four billion years ago.
- 339. We now know
that there are deep seas
- 340. on the moons of Jupiter and Saturn.
- 341. If life can exist under
such extreme conditions down here,
- 342. then surely it could exist
somewhere out there.
- 343. Next time, we travel
to bustling coral reefs.
- 344. Here, animals must go
to extraordinary lengths
- 345. to get ahead of the competition
in these crowded cities.