1 00:01:25,920 --> 00:01:30,619 Most of the earth is covered by water. 2 00:01:31,192 --> 00:01:33,592 In fact, two-thirds of it is. 3 00:01:34,495 --> 00:01:37,020 And it's only in this generation 4 00:01:37,198 --> 00:01:44,536 that we have been able to move about it with any degree of freedom as I am doing now. 5 00:01:45,506 --> 00:01:53,003 So perhaps it is not surprising that still most of this vast domain 6 00:01:53,180 --> 00:01:54,841 is still unexplored. 7 00:01:55,950 --> 00:01:59,215 And in the geographical sense, 8 00:02:00,087 --> 00:02:03,989 the surface of the sea, the floor of the sea, 9 00:02:04,959 --> 00:02:08,395 is even more varied than the surface of the land. 10 00:02:25,479 --> 00:02:30,314 To see just how varied it is, let's take an imaginary journey across the Pacific 11 00:02:30,484 --> 00:02:34,580 starting in the west where the ocean is deeper than anywhere else on the globe: 12 00:02:34,755 --> 00:02:36,416 The Mariana trench. 13 00:02:37,258 --> 00:02:43,197 The bottom of this immense valley seven miles below the surface is grooved by deep faults. 14 00:02:43,898 --> 00:02:45,832 If Mount Everest rose from the bottom, 15 00:02:46,100 --> 00:02:50,196 its summit would still be beneath 7,000 feet of water. 16 00:02:51,205 --> 00:02:55,972 Down at the very bottom, the water pressure is some seven tons per square inch, 17 00:02:56,277 --> 00:02:59,405 the temperature is close to freezing, and it's pitch-dark, 18 00:02:59,813 --> 00:03:02,111 for it is far beyond the reach of sunlight. 19 00:03:15,963 --> 00:03:21,265 As we climb up out of the trench, we move onto a plain covered with reddish mud. 20 00:03:28,275 --> 00:03:33,872 A few hills rise from it, but there are still some 20,000 feet of water above us. 21 00:03:35,716 --> 00:03:38,344 Travel eastwards over these plains for 1,000 miles, 22 00:03:38,519 --> 00:03:41,488 and we reach a range of fantastic mountains. 23 00:03:41,922 --> 00:03:44,652 Their summits are covered by a white deposit like snow, 24 00:03:44,825 --> 00:03:46,918 composed of the limestone skeletons 25 00:03:47,094 --> 00:03:51,190 of microscopic organisms that have drifted down from the surface. 26 00:03:51,765 --> 00:03:56,634 Before they reach the lower slopes, the water pressure becomes so great they dissolve. 27 00:03:59,540 --> 00:04:04,910 Currents sweeping up from the south pile the sand into dunes 150 feet high 28 00:04:05,079 --> 00:04:10,210 which advance slowly across the sea floor as dunes do in a desert on land. 29 00:04:14,822 --> 00:04:19,850 In places, the sand is littered with metallic lumps, some as big as cannon balls: 30 00:04:20,327 --> 00:04:24,889 Manganese that under these pressures has precipitated out from the salty water. 31 00:04:35,643 --> 00:04:40,740 After a journey of 4,000 miles, we reach the biggest mountains of all. 32 00:04:41,115 --> 00:04:44,448 These are the flanks of the great volcanic islands of Hawaii. 33 00:04:44,852 --> 00:04:47,821 Their sides are steeper than any mountain on land 34 00:04:47,988 --> 00:04:51,389 for they are never eroded by frost or by rivers armed with gravel. 35 00:04:51,725 --> 00:04:55,525 They rise from the sea floor 15,000 feet to the surface 36 00:04:55,696 --> 00:04:58,756 and continue for an almost equal height above it, 37 00:04:59,033 --> 00:05:02,992 so they can truly be reckoned the highest mountains in the world. 38 00:05:05,472 --> 00:05:07,770 As we climb up their sides towards the surface, 39 00:05:07,941 --> 00:05:12,037 we return once more to light and to abundant life. 40 00:05:19,453 --> 00:05:23,787 Life began in sunlit waters like these some 3,000 million years ago, 41 00:05:24,124 --> 00:05:27,218 and creatures very similar to those ancient primeval organisms 42 00:05:27,394 --> 00:05:30,693 still flourish in shallow seas all over the world. 43 00:05:31,765 --> 00:05:37,795 Feather stars like these waved their tentacles long before any fish appeared, 44 00:05:37,971 --> 00:05:41,463 at a time when the land was still bare of life of any kind. 45 00:05:49,883 --> 00:05:53,114 Horseshoe crabs come from an equally antique stock. 46 00:05:53,387 --> 00:05:56,879 Fossils have been found in rocks 600 million years old. 47 00:05:57,925 --> 00:05:59,415 Most of their relatives have died out. 48 00:05:59,660 --> 00:06:04,597 These are the lonely survivors of a widespread and successful group. 49 00:06:23,317 --> 00:06:26,650 Even older, indeed among the first of all living things, 50 00:06:26,854 --> 00:06:30,119 microscopic plants encased in shells of limestone. 51 00:06:30,624 --> 00:06:35,186 They use sunshine to build, from simple chemicals in the sea water, their own tissue. 52 00:06:35,896 --> 00:06:39,229 This act of photosynthesis, transforming mineral into vegetable, 53 00:06:39,400 --> 00:06:42,096 is the basis of all life in the sea. 54 00:06:47,541 --> 00:06:49,236 A myriad of creatures feed on them. 55 00:06:49,576 --> 00:06:55,242 Some are tiny animals, scarcely bigger than the plants that they waft into their mouths. 56 00:07:02,055 --> 00:07:05,718 This floating community of plants and animals is the plankton. 57 00:07:06,059 --> 00:07:09,358 Its members move endlessly through the blue seas. 58 00:07:09,563 --> 00:07:14,933 Many are fragile constructions ofjelly that would collapse without the support of water. 59 00:07:25,245 --> 00:07:28,339 Some are colonial, several feet long. 60 00:07:37,191 --> 00:07:40,888 They call this Venus's girdle. It's two feet acros 61 00:07:41,094 --> 00:07:44,222 Light catches in the beating hairs that ripple over its body 62 00:07:44,398 --> 00:07:47,162 as it moves slowly through the water. 63 00:07:50,237 --> 00:07:53,638 The animals of the plankton, all those that can't photosynthesise, 64 00:07:53,807 --> 00:07:59,143 sweep up the tiny plants and other edible particle in many different ways. 65 00:08:01,715 --> 00:08:07,017 This one extends a forest of long tentacles in which smaller organisms get entangled. 66 00:08:09,323 --> 00:08:12,918 This, transparent as glass, trails stinging thread 67 00:08:13,093 --> 00:08:16,028 and pulls them in whenever they catch something. 68 00:08:30,377 --> 00:08:32,811 Worms actively pursue their prey. 69 00:08:41,255 --> 00:08:45,817 Creatures from many families of animals have representatives in this community. 70 00:08:46,059 --> 00:08:49,722 Some are permanent members, some only temporary, 71 00:08:49,897 --> 00:08:53,298 joining it when they are young larvae and drifting great distances 72 00:08:53,467 --> 00:08:57,836 before they grow up, change shape and settle down to a more static life. 73 00:08:58,305 --> 00:09:03,242 But all are ultimately dependent on the tiny microscopic plants. 74 00:09:13,654 --> 00:09:16,885 There is another way in which the drifting particles of food can be gathered. 75 00:09:17,124 --> 00:09:20,924 Instead of moving with the current, you stay fixed to the rocks 76 00:09:21,094 --> 00:09:24,063 and allow the currents to bring food to you. 77 00:09:24,531 --> 00:09:28,092 That is the technique used by anemones and many other creatures. 78 00:09:30,804 --> 00:09:35,935 As the water sweeps by, the particles it carries stick to the waving tentacles. 79 00:09:47,254 --> 00:09:51,850 All kinds of creatures live in this fashion. This is a sea cucumber. 80 00:09:58,532 --> 00:10:01,023 And this, a basket star. 81 00:10:12,512 --> 00:10:15,948 The water brings not only food but vital oxygen. 82 00:10:16,149 --> 00:10:18,811 If it doesn't bring it fast enough, it can be speeded 83 00:10:18,986 --> 00:10:21,716 by pulsing as these coral polyps are doing. 84 00:10:27,327 --> 00:10:31,821 It's not only simple creatures like anemones and corals that filter currents. 85 00:10:32,099 --> 00:10:35,557 Other more complex animals have also taken to doing so. 86 00:10:35,769 --> 00:10:39,466 This is a remote relative of the shrimps that has settled down on its back, 87 00:10:39,640 --> 00:10:44,805 grown a protective shell and fishes for the passing particles with its feet 88 00:10:53,587 --> 00:10:54,918 It's a barnacle. 89 00:10:58,992 --> 00:11:02,359 Some crabs also rely on the currents to bring them meals, 90 00:11:02,529 --> 00:11:05,794 and pluck them from the water with tiny pincers. 91 00:11:10,704 --> 00:11:16,506 But the biggest of all filter-feeders propel themselves gently through the surface waters. 92 00:11:23,183 --> 00:11:25,879 A manta ray, 18 feet across. 93 00:11:26,286 --> 00:11:27,583 It often feeds at night 94 00:11:27,754 --> 00:11:31,588 when dense swarms of the plankton move up towards the surface. 95 00:11:32,092 --> 00:11:35,960 The water is channelled into its mouth by the blades on the sides of its head, 96 00:11:36,129 --> 00:11:40,259 then passes through filters in the slits in the sides of its throat. 97 00:11:47,407 --> 00:11:51,969 The basking shark gathers the same sort of food in a similar way. 98 00:11:52,512 --> 00:11:57,916 It grows even bigger than the manta: 40 feet long and four tons in weight. 99 00:12:00,921 --> 00:12:06,120 Idling through the water, it filters over 1,000 tons of water every hour. 100 00:12:17,637 --> 00:12:23,132 And even bigger still, in fact, the biggest of all fish: The whale shark. 101 00:12:24,845 --> 00:12:28,804 This mountain of a creature can be up to 50 feet long. 102 00:12:40,961 --> 00:12:47,161 Other, more normal-sized fish live on and around it. Some collect its refuse. 103 00:12:56,309 --> 00:13:02,043 Others pick off morsels that get stuck in its tiny teeth in a mouth six feet wide. 104 00:13:03,784 --> 00:13:09,245 It's an astonishing proof of how sustaining and how abundant the plankton must be. 105 00:13:20,467 --> 00:13:25,302 But of course, not all sharks live on plankton or are quite so amiable. 106 00:13:28,141 --> 00:13:31,702 These are grey reef sharks, about six feet long. 107 00:13:43,657 --> 00:13:48,924 It's some consolation to know that those sharks don't normally attack human beings. 108 00:13:49,262 --> 00:13:54,495 Their prey is usually small fish or predators. 109 00:13:55,168 --> 00:14:02,939 And indeed, when one looks at them, it is not so much their danger that comes into your mind 110 00:14:03,109 --> 00:14:05,043 as their extraordinary beauty. 111 00:14:05,679 --> 00:14:08,580 They are so perfectly streamlined, 112 00:14:08,748 --> 00:14:11,911 every curve of their body, every curve of their fi 113 00:14:12,085 --> 00:14:19,423 precisely matching the shape that is needed to glide through the water with the least struggle 114 00:14:19,926 --> 00:14:21,416 Most beautiful things. 115 00:14:23,530 --> 00:14:28,832 Sharks belong to a very ancient family that evolved this shape some 400 million years ago. 116 00:14:29,102 --> 00:14:33,038 But soon after they appeared, another group of fish established itself. 117 00:14:35,308 --> 00:14:38,709 These have skeletons of bone, not gristle as the sharks have, 118 00:14:38,879 --> 00:14:41,871 and they have two swimming aids that the sharks lack: 119 00:14:42,182 --> 00:14:44,377 Swim bladders that give them buoyancy 120 00:14:44,551 --> 00:14:47,577 and paired fins that can twist in all directions 121 00:14:47,754 --> 00:14:50,245 and so give them great manoeuvrability in the water. 122 00:14:50,924 --> 00:14:55,623 These bony fish are the ones which today dominate the seas. 123 00:15:22,389 --> 00:15:26,485 Among them are the most powerful of all hunters in the sea: The tuna. 124 00:15:26,893 --> 00:15:29,953 When hunting, they can swim faster than any other fish. 125 00:15:30,130 --> 00:15:35,727 Some say nearly 70 miles an hour, faster even than a cheetah can run on land. 126 00:15:36,903 --> 00:15:39,963 But the fish's dominance of the sea didn't go unchallenged. 127 00:15:40,173 --> 00:15:45,805 Ten million years ago, warm-blooded creatures from the land invaded the sea, mammals, 128 00:15:45,979 --> 00:15:48,641 and they became equally streamlined. 129 00:16:18,378 --> 00:16:20,972 Dolphins and killer whales are descended 130 00:16:21,147 --> 00:16:26,210 from four-footed, land-living, air-breathing mammals that were flesh-eaters. 131 00:16:26,686 --> 00:16:30,986 In the sea, they lost their limbs but not their taste for meat, nor their teeth. 132 00:16:31,324 --> 00:16:35,351 Indeed, one of the family that lives only in the ice-strewn waters of the Arctic 133 00:16:35,528 --> 00:16:39,294 has grown one of its teeth to an extraordinary length. 134 00:16:48,975 --> 00:16:51,671 These are narwhals, and they are all males, 135 00:16:51,845 --> 00:16:55,804 for only the male produces the tusk, up to nine feet long. 136 00:16:59,686 --> 00:17:03,554 These without tusks are females, one with a calf. 137 00:17:04,257 --> 00:17:06,350 And these are young males. 138 00:17:12,599 --> 00:17:15,693 No one knows for certain what purpose the tusk serves, 139 00:17:15,869 --> 00:17:18,394 but it seems likely that it is used in courtship. 140 00:17:18,772 --> 00:17:22,230 That is confirmed by the fact that very rarely indeed 141 00:17:22,409 --> 00:17:26,277 males have been glimpsed, as here, fencing with one another. 142 00:17:53,373 --> 00:17:58,401 The best view that most of us can get for most of the time of most kinds of whales 143 00:17:58,578 --> 00:18:03,743 is a brief glimpse as the animal comes to the surface to snatch a breath, 144 00:18:03,983 --> 00:18:09,319 but that's not the case with the beluga, these beautiful white whales. 145 00:18:09,689 --> 00:18:14,991 Up here in the Canadian Arctic, they come during those brief weeks 146 00:18:15,161 --> 00:18:17,595 when the ice goes away from these shores, 147 00:18:17,797 --> 00:18:21,665 and assemble in vast numbers in this bay. 148 00:18:22,001 --> 00:18:25,562 There are hundreds, sometimes as many as a thousand. 149 00:18:33,113 --> 00:18:37,812 We don't really know why they come here, nor what they do now that they are here. 150 00:18:38,051 --> 00:18:41,782 Maybe there is some kind of specially attractive food in these shallow waters, 151 00:18:41,988 --> 00:18:46,391 for they seem to stir up the gravelly bottom of the bay. 152 00:18:46,993 --> 00:18:51,293 Perhaps there is valuable food for youngsters or nursing mothers, 153 00:18:51,564 --> 00:18:55,295 for many that come are females with babies a few months old, 154 00:18:55,468 --> 00:18:58,062 swimming skilfully in their mother's slipstream. 155 00:18:58,371 --> 00:19:02,831 Whatever it is that they do here, they seem to be enjoying themselves hugely. 156 00:19:08,548 --> 00:19:11,949 And they haven't lost their mammalian habit of communicating by sound. 157 00:19:12,418 --> 00:19:16,115 So vocal are they that they are sometimes called sea canaries. 158 00:19:24,664 --> 00:19:28,031 The most recent family to colonise the sea, also mammals, 159 00:19:28,201 --> 00:19:30,635 were descended from bear-like creatures. 160 00:19:31,437 --> 00:19:33,302 The walrus and its cousin the seals 161 00:19:33,473 --> 00:19:38,672 are not so fully adapted to life in the sea as the whales, but they haven't been there so long. 162 00:19:46,519 --> 00:19:51,547 They haven't lost their feet as the whales have, nor do they spend all their lives in the water. 163 00:19:55,361 --> 00:19:58,990 They come ashore to give birth and they often haul themselves out to rest. 164 00:19:59,432 --> 00:20:01,525 Nonetheless, they are superb swimmers. 165 00:20:11,044 --> 00:20:15,845 So, in the 3,000 million years since living organisms first appeared in the sea, 166 00:20:16,015 --> 00:20:19,781 the oceans have acquired a population of immense diversity, 167 00:20:19,953 --> 00:20:22,751 from single-celled microscopic plants 168 00:20:22,922 --> 00:20:26,380 to advanced and complex highly intelligent mammals. 169 00:20:26,859 --> 00:20:31,228 Indeed, there are more different groups of animals living in the sea than there are on lan 170 00:20:34,701 --> 00:20:37,864 The oceans were the birthplace and the nursery of life, 171 00:20:38,037 --> 00:20:40,562 and they are still its main residence. 172 00:21:34,961 --> 00:21:36,895 But the sea is not uniform. 173 00:21:37,130 --> 00:21:40,031 Just as land has different, specialised environments 174 00:21:40,199 --> 00:21:44,499 inhabited by creatures that occur nowhere else, so does the sea. 175 00:21:45,138 --> 00:21:50,804 The coral lagoon is a world of its own. Corals are very demanding in their requirements. 176 00:21:51,044 --> 00:21:55,071 They must have good light, clear, unpolluted water and warmth, 177 00:21:55,248 --> 00:21:58,775 and they find this in the tropics, 178 00:21:59,018 --> 00:22:03,148 particularly around the small islands that are the summits of submarine mountains. 179 00:22:03,389 --> 00:22:07,189 There, they flourish so well that they grow outwards into the clear blue water, 180 00:22:07,360 --> 00:22:12,423 building on top of their own skeletons to form wide, shallow lagoons. 181 00:22:17,203 --> 00:22:21,469 The variety of corals is immense. Some are soft and rubbery, 182 00:22:21,641 --> 00:22:26,601 others are hard and slightly flexible, like a horn But most are stony. 183 00:22:27,380 --> 00:22:32,943 The organisms that build these structures, ton upon ton, occupy only the outer skin. 184 00:22:33,319 --> 00:22:37,983 The rest is dead. As they develop, the little organisms branch, 185 00:22:38,157 --> 00:22:41,149 and the particular way they do so determines the shape of the colony, 186 00:22:41,327 --> 00:22:47,129 forming antlers and organ pipes, whips and fans, vases and buttons. 187 00:23:01,214 --> 00:23:05,548 If the jungle is the place on land 188 00:23:06,018 --> 00:23:11,979 where there are the greatest number and the greatest variety of life, 189 00:23:12,692 --> 00:23:19,097 then this, the coral reef, is surely the jungle of the sea. 190 00:23:19,832 --> 00:23:21,595 The number, the variety, 191 00:23:21,768 --> 00:23:29,174 the sheer beauty of all these myriad fish, corals and anemones, is quite breathtaking. 192 00:23:31,911 --> 00:23:38,612 Of course, the tiny anemone-like creatures that build these fans and fronds of coral 193 00:23:38,785 --> 00:23:40,252 are themselves animals. 194 00:23:41,053 --> 00:23:49,961 But within their tissues, there are tiny granules which are algae, plants, 195 00:23:50,329 --> 00:23:57,997 and it's they that harness the sunshine and use it to build living tissue. 196 00:23:58,538 --> 00:24:02,201 And onto these plates and branches of coral 197 00:24:02,375 --> 00:24:05,970 come a wide variety of creatures to browse. 198 00:24:07,880 --> 00:24:10,542 Some, like the parrotfish, bite off chunks. 199 00:24:10,783 --> 00:24:15,311 Others pick off little organisms and particles with the utmost delicacy. 200 00:24:33,239 --> 00:24:35,867 The tides, surging in and out of the lagoon, 201 00:24:36,042 --> 00:24:40,843 bring in regular supplies of fresh oxygenated water and fresh food. 202 00:24:41,147 --> 00:24:46,608 Angler fish sit in the current waiting patiently, like all fishermen, for whatever turns up. 203 00:24:46,886 --> 00:24:51,414 Even such specialised fish as these exist on the reef in several different versions. 204 00:24:51,624 --> 00:24:56,152 There's this lemon-yellow one that angles with a movable spine on its forehead. 205 00:25:03,202 --> 00:25:06,194 Little reef fish find it an irresistible bait. 206 00:25:15,047 --> 00:25:18,813 More prey to be angled for by the decoy fish. 207 00:25:27,293 --> 00:25:32,458 A dorsal fin patterned with a false eye and mouth so that it looks like a little fish 208 00:25:32,632 --> 00:25:37,433 and may attract other small fish or possibly predatory ones. 209 00:25:38,738 --> 00:25:41,901 This one is the wrong way round. Its spines would stick in the mouth. 210 00:25:46,712 --> 00:25:47,838 That's better. 211 00:25:48,814 --> 00:25:51,476 One of the fastest actions in the animal world. 212 00:25:54,887 --> 00:25:57,981 And the angler, perhaps to prevent a second fish arriving 213 00:25:58,157 --> 00:25:59,920 before it has digested the first, 214 00:26:00,092 --> 00:26:03,084 changes colour so that the lure vanishes. 215 00:26:09,702 --> 00:26:12,728 In the reef, there are many species with many ways of life. 216 00:26:13,005 --> 00:26:15,166 Just take the crustaceans, for example. 217 00:26:15,508 --> 00:26:17,703 Hermit crabs live by scavenging. 218 00:26:17,944 --> 00:26:22,040 Often, they share the shells they have commandeered as a home with anemones. 219 00:26:23,583 --> 00:26:26,746 The anemones benefit by picking up bits of the crab's meal 220 00:26:26,919 --> 00:26:31,288 and give the crab in return a certain protection with their stinging tentacles. 221 00:26:33,292 --> 00:26:36,693 This crab actually uses a particular kind of anemone as a weapon, 222 00:26:36,963 --> 00:26:39,363 wearing one on each claw like boxing gloves. 223 00:26:42,068 --> 00:26:44,866 This one tries to put on a sponge like an overcoat. 224 00:26:45,104 --> 00:26:49,097 It's rather overdoing things, for the brown jersey it's wearing 225 00:26:49,275 --> 00:26:51,937 is also a sponge, and a well-established one. 226 00:26:52,278 --> 00:26:54,269 But the arrangement will suit both parties. 227 00:26:54,480 --> 00:26:58,849 The crab gets the camouflage and the sponge may benefit from the crab's crumbs. 228 00:27:05,458 --> 00:27:07,824 Crabs and their relations, the lobsters and shrimps, 229 00:27:07,994 --> 00:27:10,224 are found from top to bottom of the reef. 230 00:27:10,630 --> 00:27:14,726 Big ones like this lobster prowl openly through the coral branches. 231 00:27:20,706 --> 00:27:25,268 Little ones like the mantis shrimp are rather more cautious and build themselves tunnels. 232 00:27:35,254 --> 00:27:37,814 If the coral reef is the equivalent of the jungle, 233 00:27:37,990 --> 00:27:43,360 maybe these waving beds of kelp in the cold Atlantic waters off the coast of Norway 234 00:27:43,529 --> 00:27:46,862 are like the dark evergreen forests of the north, 235 00:27:47,133 --> 00:27:52,400 bitterly cold, dense and uniform, and swept by raging gales. 236 00:28:12,591 --> 00:28:16,186 Bleak though the kelp forest may seem, there are riches here, 237 00:28:16,362 --> 00:28:18,330 and eider duck know it. 238 00:28:30,543 --> 00:28:34,570 The eiders settle in flocks on the surface of the water above the kelp forest, 239 00:28:34,747 --> 00:28:39,377 and they are almost as adept in flying through the water as they are through the air. 240 00:28:57,069 --> 00:29:00,061 This is what they seek: Mussels. 241 00:29:09,548 --> 00:29:14,178 Eiders are true creatures of the sea, seldom, if ever, visiting fresh water. 242 00:29:14,353 --> 00:29:19,017 They prefer to fish for mussels on an ebb tide when the water is low, 243 00:29:19,191 --> 00:29:23,025 but they can stay below water for a minute or more, 244 00:29:23,195 --> 00:29:26,460 and dive down to 50 feet below the surface. 245 00:29:36,442 --> 00:29:40,708 The streaming current causes great problems to the fish of the kelp forest. 246 00:29:40,946 --> 00:29:43,506 Simply maintaining a position there is a struggle. 247 00:29:43,682 --> 00:29:47,743 The lumpsucker does it with modified fins on its underside, 248 00:29:48,020 --> 00:29:53,219 and gets such a firm grip that it is extremely difficult to pull it off. 249 00:29:53,392 --> 00:29:55,792 Its young develop suckers at a very early age 250 00:29:55,961 --> 00:30:00,921 and sometimes fix themselves to their father, who ferries them off to deeper waters. 251 00:30:04,103 --> 00:30:06,970 Kelp grows in coastal waters all round the world, 252 00:30:07,139 --> 00:30:09,903 and in the seaweed forests of southern Australia 253 00:30:10,075 --> 00:30:14,068 lives one of the most extravagantly camouflaged of all fish. 254 00:30:23,589 --> 00:30:26,387 Other fish appear to be completely deceived. 255 00:30:26,659 --> 00:30:29,025 This small one, itself with a false eye 256 00:30:29,195 --> 00:30:31,823 so that it is difficult to tell whether it is coming or going, 257 00:30:31,997 --> 00:30:37,799 lives in these green leafy tatters as though they were real plants, but they're not. 258 00:30:38,037 --> 00:30:42,565 They're all part of the elaborate costume of the leafy seadragon. 259 00:31:13,405 --> 00:31:15,635 The dragon is a kind of a seahorse, 260 00:31:15,808 --> 00:31:20,905 as you can see if you disentangle its main body from its extraordinary outgrowths. 261 00:31:21,247 --> 00:31:26,583 Like its relatives, it has a tiny mouth with which it picks up small shrimps 262 00:31:26,752 --> 00:31:31,121 that ill-advisedly take shelter in what appears to be floating weed. 263 00:32:05,057 --> 00:32:08,618 As well as its forests, the sea has its deserts. 264 00:32:08,961 --> 00:32:14,695 Over vast areas of the ocean floor, there is nothing but shifting wastes of sand. 265 00:32:16,435 --> 00:32:20,633 It seems as lifeless as a desert on land in the heat of the day. 266 00:32:24,510 --> 00:32:29,072 An occasional fish wanders over the rippled surface as though lost. 267 00:32:31,717 --> 00:32:34,652 Here and there, a sea urchin levers itself along, 268 00:32:34,820 --> 00:32:39,223 extracting what nutriment it can find from particles within the sand. 269 00:32:44,430 --> 00:32:49,732 The goatfish looks for the same sort of thing, using sensitive barbels on its chin. 270 00:32:56,508 --> 00:33:00,774 To build a home or a shelter in sand demands special techniques. 271 00:33:01,413 --> 00:33:04,905 Garden eels cement grains together with mucus to form a tube 272 00:33:05,084 --> 00:33:09,487 in which they cling with their tails while collecting plankton with their mouths. 273 00:33:11,323 --> 00:33:15,054 Bulldozer shrimps and a goby cooperate to build a shared tunnel, 274 00:33:15,227 --> 00:33:17,752 using coral rubble to prop up the roof. 275 00:33:38,317 --> 00:33:42,253 The bladefish can improvise a shelter on the spur of the moment. 276 00:33:50,896 --> 00:33:53,091 There are two very different reasons for hiding. 277 00:33:53,298 --> 00:33:56,665 The bladefish does it to get out of trouble. 278 00:34:00,305 --> 00:34:02,273 This little cuttlefish does it... 279 00:34:04,543 --> 00:34:06,670 ...in order to cause trouble. 280 00:34:20,893 --> 00:34:22,918 The prey is a shrimp. 281 00:34:49,988 --> 00:34:53,754 And the cuttlefish has the shrimp firmly in its tentacles. 282 00:35:07,840 --> 00:35:11,970 The floating pastures of plankton on which so many ocean-going fish depend 283 00:35:12,144 --> 00:35:15,910 must live in the surface waters within the reach of sunshine. 284 00:35:16,381 --> 00:35:21,341 The coral lagoon and the kelp forests only flourish where good light reaches the bottom. 285 00:35:21,820 --> 00:35:25,187 But light can't penetrate much beyond 350 feet, 286 00:35:25,357 --> 00:35:29,316 and most of the ocean floor lies far deeper that that. 287 00:35:37,903 --> 00:35:41,930 Even quite near the surface you have to take your own light with you. 288 00:35:52,784 --> 00:35:55,014 Fish, too, carry lights. 289 00:36:00,592 --> 00:36:03,652 The flashlight fish use theirs to find their food 290 00:36:03,829 --> 00:36:08,857 and to maintain contact like other species in deeper water. 291 00:36:10,302 --> 00:36:14,932 Their batteries are little colonies of bacteria living in a pouch beneath the fish's eye 292 00:36:15,107 --> 00:36:18,201 that give off light as a by-product of their chemistry, 293 00:36:18,377 --> 00:36:23,679 and the fish turns its lights off and on by raising and lowering a flap of skin. 294 00:36:28,387 --> 00:36:33,586 At greater depths, giant amphipods, primitive relatives of the horseshoe crabs, 295 00:36:33,759 --> 00:36:35,317 plod along the bottom. 296 00:36:36,128 --> 00:36:39,325 Very little is known about these strange creatures. 297 00:37:01,553 --> 00:37:04,920 Even at 3,000 feet down there is life. 298 00:37:05,290 --> 00:37:09,659 Almost all the creatures here feed on dead bodies that fall from above. 299 00:37:09,895 --> 00:37:12,693 The eel-like hagfish, which have no jaws, 300 00:37:12,864 --> 00:37:16,197 knot themselves against the carcass to get a better hold. 301 00:37:30,215 --> 00:37:34,948 Bigger fish grip with their teeth and spin, tearing off strips of the flesh. 302 00:37:37,456 --> 00:37:39,822 The smaller particles drifting down from the surface 303 00:37:39,992 --> 00:37:43,257 are collected by deep-sea stars and smaller fish. 304 00:37:43,495 --> 00:37:47,955 It is here that all the nutrients produced by decay finally collect as ooze. 305 00:37:48,300 --> 00:37:52,396 The very deepest parts of the ocean lie below the paths of currents, 306 00:37:52,571 --> 00:37:56,667 so the water is not only black and cold but almost still. 307 00:37:59,077 --> 00:38:03,946 The weird tripod fish perches on its extended fins and its tail. 308 00:38:09,688 --> 00:38:15,092 Even in the deepest place of all, the Mariana trench, seven miles down, there is life. 309 00:38:15,961 --> 00:38:18,759 Shrimps are slowly picking clean the skeleton of a fish 310 00:38:18,930 --> 00:38:23,333 that may have taken months to drift down to these still depths. 311 00:38:29,875 --> 00:38:33,504 But at the surface of the sea, the water is never still. 312 00:38:46,325 --> 00:38:50,728 Storms whip it up into great waves which may travel for hundreds of miles 313 00:38:50,896 --> 00:38:53,922 before, eventually, they crash into the coasts. 314 00:39:04,509 --> 00:39:07,034 The water in these waves doesn't travel far, 315 00:39:07,212 --> 00:39:11,979 but circulates more or less in the same place while the wave itself moves on. 316 00:39:12,951 --> 00:39:16,387 But that circulation is of crucial importance to the creatures of the sea, 317 00:39:16,555 --> 00:39:22,687 for it is this that allows the waters of the sea to absorb the vital oxygen from the air above. 318 00:40:02,667 --> 00:40:05,568 But deep currents do move through the oceans. 319 00:40:05,937 --> 00:40:07,928 They are created by the spin of the earth 320 00:40:08,106 --> 00:40:11,098 which gives the waters at the equator a westward drift, 321 00:40:11,276 --> 00:40:17,010 and by the sun which warms these equatorial waters and sends them away to the poles. 322 00:40:17,649 --> 00:40:23,383 This produces vast ocean-wide eddies that replicate the whirlpools of tidal races, 323 00:40:23,555 --> 00:40:27,582 but do so on a scale that is thousands of miles across. 324 00:40:32,631 --> 00:40:35,725 In the Pacific, the equatorial current divides, 325 00:40:35,901 --> 00:40:39,132 and in the south it flows down as far as New Zealand. 326 00:40:41,873 --> 00:40:45,070 In the Indian Ocean, the southern system is almost circular. 327 00:40:45,310 --> 00:40:48,302 The northern has to swirl around the great triangle of India. 328 00:40:51,249 --> 00:40:54,946 In the Atlantic, the north-flowing current is called the Gulf Stream, 329 00:40:55,120 --> 00:40:59,955 and it encloses, in the centre of the ocean, as all these great whirlpools do, 330 00:41:00,125 --> 00:41:02,992 an area where the waters are almost still. 331 00:41:05,197 --> 00:41:09,759 On their surface float rafts of weed. It never roots but floats for ever, 332 00:41:09,935 --> 00:41:15,100 rocked sufficiently by the swell to prevent its topmost fronds from drying out in the sun. 333 00:41:23,281 --> 00:41:24,339 The Portuguese sailors, 334 00:41:24,516 --> 00:41:29,283 looking at the little bladders that keep it afloat called them sargasso: Grapes. 335 00:41:29,788 --> 00:41:31,517 This is the Sargasso Sea. 336 00:41:31,990 --> 00:41:36,552 Like every other region within the oceans, it has its own specialised inhabitants. 337 00:41:38,797 --> 00:41:43,598 Small fish shelter in its fronds and are closely disguised to match them, 338 00:41:43,768 --> 00:41:48,467 and swimming crabs clamber up and rest on top of the floating mats. 339 00:41:49,374 --> 00:41:54,209 But the Sargasso is one of the least fertile stretches of water in all the oceans. 340 00:41:54,613 --> 00:41:58,344 Since no currents feed into it, it receives no nutrients 341 00:41:58,517 --> 00:42:01,418 and its clear waters are largely barren. 342 00:42:06,625 --> 00:42:08,991 But patches of it occasionally break away. 343 00:42:12,697 --> 00:42:14,858 Between the Gulf Stream and the North American coast 344 00:42:15,033 --> 00:42:19,402 there are cores of cold Sargasso water surrounded by warm circulating currents 345 00:42:19,571 --> 00:42:24,440 formed when the Gulf Stream meanders and nips off a segment of the Sargasso, 346 00:42:24,609 --> 00:42:27,100 complete with its weed and populations of animals. 347 00:42:27,512 --> 00:42:30,572 These warm core-rings, a hundred or so miles across, 348 00:42:30,749 --> 00:42:34,708 drift down the coast until they lose their momentum and their warmth, 349 00:42:34,886 --> 00:42:38,083 break up and are swept away again by the Gulf Stream. 350 00:42:39,958 --> 00:42:44,452 The Gulf Stream continues northwards along the coast to Newfoundland. 351 00:42:46,598 --> 00:42:51,058 Here, off these bleak fogbound beaches, it creates an area of seas 352 00:42:51,236 --> 00:42:56,003 that might be seen as one of the most fertile and productive places on the entire globe, 353 00:42:56,274 --> 00:42:59,732 a place where the full potential richness of the ocean is realised, 354 00:42:59,911 --> 00:43:04,905 and where animals of all kinds come to harvest it. 355 00:43:09,154 --> 00:43:14,057 The warm water of the Gulf Stream is accompanied by steady warm breezes. 356 00:43:14,593 --> 00:43:20,725 And just about here, it meets a cold current coming down from the Arctic, 357 00:43:20,999 --> 00:43:25,936 and where the warm breezes meet the icy breath of the Arctic, 358 00:43:26,371 --> 00:43:29,431 they shed their moisture and form these fogs. 359 00:43:29,774 --> 00:43:34,336 And where the two currents meet, the waters churn and swirl, 360 00:43:34,512 --> 00:43:38,972 and bring up rich nutrients from the bottom of the sea. 361 00:43:39,284 --> 00:43:41,980 Now, it so happens thatjust off this coast 362 00:43:42,153 --> 00:43:45,680 there is an underwater plateau where the water is so shallow 363 00:43:45,857 --> 00:43:50,419 that the sun or the light can get almost always to the bottom, 364 00:43:50,762 --> 00:43:55,563 and so the floating plants of the sea are always within the range of light, 365 00:43:55,734 --> 00:44:00,967 and they're fed eternally by these swirling currents bringing up nutrients. 366 00:44:01,706 --> 00:44:06,006 So the plants flourish, and on them come great shoals of fish 367 00:44:06,177 --> 00:44:09,078 which breed and spawn in such numbers 368 00:44:09,247 --> 00:44:13,206 that at times the waters seem almost to boil with them. 369 00:44:14,386 --> 00:44:18,516 These are capelin, a small fish related to the European smelt. 370 00:44:18,890 --> 00:44:21,188 They feed on the plankton in the surface waters, 371 00:44:21,359 --> 00:44:25,295 and in May they gather in vast shoals to spawn. 372 00:44:25,630 --> 00:44:27,291 Some will do so offshore, 373 00:44:27,465 --> 00:44:31,526 but some go to extraordinary trouble to lay their eggs out of water 374 00:44:31,703 --> 00:44:34,137 where they will be safe from other hungry fish. 375 00:44:37,509 --> 00:44:40,603 The shoals come closer and closer inshore. 376 00:44:48,853 --> 00:44:52,516 Each female capelin can produce 10,000 eggs. 377 00:44:52,891 --> 00:44:57,385 Each wave brings in tens of thousands of fish again and again. 378 00:44:57,862 --> 00:45:00,592 The number of eggs defies any computation. 379 00:45:00,899 --> 00:45:04,835 They pile up in banks, as solid as sand along the high-water mark. 380 00:45:07,005 --> 00:45:11,305 Having spawned, all the males and most of the females die. 381 00:45:25,523 --> 00:45:28,117 The richness that the capelin gathered from the plankton 382 00:45:28,293 --> 00:45:32,491 and converted into their own flesh is now gathered by birds. 383 00:45:34,299 --> 00:45:37,996 Shearwaters gorge themselves on the dying and the dead. 384 00:45:50,081 --> 00:45:53,949 Gannets dive between the scavengers, taking the live fish. 385 00:45:59,657 --> 00:46:04,788 And still the capelin come in. Even before they get to the shallows, they are hunted. 386 00:46:07,632 --> 00:46:13,195 Herds of seals come up to the Grand Banks specially at this time to share in the bonanza. 387 00:47:00,084 --> 00:47:03,520 And here, too, come the biggest hunters of all. 388 00:47:09,093 --> 00:47:10,651 Humpbacked whales. 389 00:47:21,139 --> 00:47:27,009 With each upward lunge, the whale takes in tons of water and thousands of capelin. 390 00:47:33,885 --> 00:47:37,218 With a mouthful in its jaws, it brings forward its tongue, 391 00:47:37,388 --> 00:47:41,484 squirts out surplus water through the filter plate that hang from its upperjaw 392 00:47:41,659 --> 00:47:43,786 and swallows the tiny fish. 393 00:48:07,118 --> 00:48:10,610 The whales have developed a way of concentrating the capelin shoals 394 00:48:10,788 --> 00:48:14,588 so that they will get the greatest number of fish in a single mouthful. 395 00:48:15,260 --> 00:48:16,989 It's called bubble-netting. 396 00:48:17,629 --> 00:48:21,224 Those white areas are huge masses of bubbles. 397 00:48:21,933 --> 00:48:24,561 The whales dive deep below the swarming capelin 398 00:48:24,736 --> 00:48:29,867 and start a slow, spiralling swim upwards, blowing gusts of bubbles as they rise. 399 00:48:30,141 --> 00:48:33,304 The capelin, frightened by the circular curtain of bubbles, 400 00:48:33,478 --> 00:48:36,743 rush inwards and form a dense, confused shoal. 401 00:48:36,981 --> 00:48:41,975 The whale rises up in the middle, jaws agape, and engulfs the lot. 402 00:48:52,397 --> 00:48:55,855 After a few short weeks, the spawning orgy of the capelin is over. 403 00:48:56,234 --> 00:49:00,170 Their bodies lie in vast drifts awaiting the processes of decay 404 00:49:00,338 --> 00:49:02,670 which will return their nutrients to the waters, 405 00:49:03,074 --> 00:49:07,977 but even before they disperse, other bodies appear: Dead squid. 406 00:49:09,347 --> 00:49:12,805 Nobody knows where they have come from, or why they have died in such numbers, 407 00:49:12,984 --> 00:49:16,044 but these blizzards of bodies appear most years in July, 408 00:49:16,220 --> 00:49:20,179 and are a sign that shoals of the living animals are about to arrive. 409 00:49:31,069 --> 00:49:33,902 They will bite any small, moving thing. 410 00:49:34,205 --> 00:49:39,541 To catch them, you don't even need bait. They simply impale themselves on a naked hook, 411 00:49:39,711 --> 00:49:45,411 so that most summers, fishing villages on the Newfoundland coast go jigging for squid, 412 00:49:45,583 --> 00:49:47,710 hauling them out by the thousands. 413 00:50:01,866 --> 00:50:05,529 As they're hooked, they puff out clouds of squid ink. 414 00:50:14,479 --> 00:50:17,607 Hundreds of tons of them are despatched every year to Japan 415 00:50:17,782 --> 00:50:20,046 where they are a much-prized food. 416 00:50:26,424 --> 00:50:32,454 Mackerel also come to the Grand Banks by the million to feed on small plankton-feeding fish 417 00:50:34,265 --> 00:50:37,496 They're netted by the ton by fleets of factory ships, 418 00:50:37,668 --> 00:50:40,796 and their rich flesh is valued all over the world. 419 00:50:42,840 --> 00:50:46,173 But even the Grand Banks are not inexhaustible. 420 00:50:47,478 --> 00:50:52,814 During this century, man has fished so skilfully, so intensively, so unrelentingly, 421 00:50:52,984 --> 00:50:56,442 that he has begun to change the pattern of life in the sea. 422 00:50:56,754 --> 00:51:00,212 Some kinds of fish have been forced to change their habits, 423 00:51:00,391 --> 00:51:03,087 others have been driven close to the edge of extinction. 424 00:51:03,428 --> 00:51:08,593 This little port in Newfoundland, close to what was once the richest of all seas, 425 00:51:08,766 --> 00:51:11,860 now brings in fewer catches, 426 00:51:12,036 --> 00:51:17,497 and modern fish-processing plants like that one are mostly standing idle. 427 00:51:17,809 --> 00:51:23,213 So man has changed the sea, just as he's changed almost every environment in the world. 428 00:51:23,381 --> 00:51:24,939 But he's done something else, too. 429 00:51:25,249 --> 00:51:27,444 He's created new environments, 430 00:51:27,618 --> 00:51:31,247 environments of brick and concrete, and chromium and plastic. 431 00:51:31,923 --> 00:51:35,017 It's the latest of the world's environments, 432 00:51:35,193 --> 00:51:38,890 and the ways in which plants and animals have adapted to live in them, 433 00:51:39,063 --> 00:51:42,328 that we're going to look at in the last of these programmes.