1 00:00:03,220 --> 00:00:04,420 Coral reefs... 2 00:00:05,980 --> 00:00:08,700 ..home to an astonishing diversity of life 3 00:00:08,700 --> 00:00:11,500 that's vital to the health of our seas. 4 00:00:14,100 --> 00:00:18,180 Lying off the coast of eastern Australia, the Great Barrier Reef 5 00:00:18,180 --> 00:00:21,420 is the world's largest expanse of coral reefs. 6 00:00:23,180 --> 00:00:27,420 But this extraordinary place and all the life that it supports 7 00:00:27,420 --> 00:00:30,580 is under threat like never before. 8 00:00:30,580 --> 00:00:35,260 Some experts predict we could lose it all in just 30 years. 9 00:00:36,900 --> 00:00:40,540 To find out what's being done to save one of the earth's greatest 10 00:00:40,540 --> 00:00:44,820 natural wonders, we've based ourselves on Heron Island 11 00:00:44,820 --> 00:00:49,060 at the southern tip of the Great Barrier Reef. 12 00:00:49,060 --> 00:00:52,980 This is one of the last healthy areas and a hub 13 00:00:52,980 --> 00:00:54,740 for pioneering research. 14 00:00:58,220 --> 00:01:02,260 By working with leading scientists, we've come here to discover 15 00:01:02,260 --> 00:01:06,460 the magnificent life found within this fragile kingdom 16 00:01:06,460 --> 00:01:07,860 of our blue planet. 17 00:01:31,220 --> 00:01:34,420 WHALE SONG ECHOES 18 00:01:39,660 --> 00:01:43,700 Positioned off the coast of Queensland, the Great Barrier Reef 19 00:01:43,700 --> 00:01:48,460 is a network of habitats where open ocean meets coral gardens 20 00:01:48,460 --> 00:01:49,980 and island paradises. 21 00:01:52,700 --> 00:01:57,140 These provide food and shelter for over 9,000 species. 22 00:01:58,940 --> 00:02:01,900 At 1,400 miles long, 23 00:02:01,900 --> 00:02:05,660 it also protects the Australian mainland by bearing the brunt 24 00:02:05,660 --> 00:02:06,980 of powerful storms. 25 00:02:17,100 --> 00:02:22,100 Each year, millions of people come from far and wide to see and study 26 00:02:22,100 --> 00:02:23,940 this natural wonder - 27 00:02:23,940 --> 00:02:27,700 the largest living structure on the planet. 28 00:02:27,700 --> 00:02:30,420 The minute you look beneath the surface, 29 00:02:30,420 --> 00:02:32,420 you are hit between the eyes 30 00:02:32,420 --> 00:02:37,220 with so much colour and so many animals. 31 00:02:37,220 --> 00:02:41,820 This underwater metropolis is made up of billions of tiny organisms 32 00:02:41,820 --> 00:02:46,380 called polyps, organised together to form a single megastructure. 33 00:02:50,140 --> 00:02:53,420 Each polyp is growing a skeleton, and the one beside it, and the one 34 00:02:53,420 --> 00:02:58,820 beside it again, until you've got hundreds, thousands, even millions 35 00:02:58,820 --> 00:03:00,540 of coral animals 36 00:03:00,540 --> 00:03:04,180 building these incredibly beautiful structures. 37 00:03:04,180 --> 00:03:07,820 These coral cities take centuries to grow 38 00:03:07,820 --> 00:03:10,100 and it's taken the Great Barrier Reef 39 00:03:10,100 --> 00:03:12,660 around 500,000 years to evolve. 40 00:03:13,860 --> 00:03:17,220 But today, its existence is under threat as the changing 41 00:03:17,220 --> 00:03:18,980 climate warms our seas. 42 00:03:21,260 --> 00:03:25,900 From our base on Heron Island, 50 miles off the Queensland coast, 43 00:03:25,900 --> 00:03:28,300 we can unearth its many riches... 44 00:03:29,980 --> 00:03:33,620 ..teaming up with the scientists who are working to both understand 45 00:03:33,620 --> 00:03:35,180 and protect it. 46 00:03:36,580 --> 00:03:41,340 Professor Peter Harrison is a global expert in coral reefs, 47 00:03:41,340 --> 00:03:45,580 having spent the last 40 years studying their inner workings. 48 00:03:51,180 --> 00:03:55,220 Heron Island provides the perfect base for him to examine corals... 49 00:03:57,540 --> 00:04:01,020 ..but to see how the whole reef functions, he needs to take 50 00:04:01,020 --> 00:04:01,980 to the air. 51 00:04:10,180 --> 00:04:13,860 The first time I flew over the reef was in the 1990s, 52 00:04:13,860 --> 00:04:16,460 and for the first time I actually got a sense of the scale 53 00:04:16,460 --> 00:04:18,300 of the whole reef. 54 00:04:18,300 --> 00:04:20,940 Extraordinary beauty at large scale. 55 00:04:22,660 --> 00:04:26,060 This is a spectacular, interconnected ecosystem. 56 00:04:33,540 --> 00:04:36,620 When looking at a reef system from the air, we start to gain a much 57 00:04:36,620 --> 00:04:39,820 better understanding of how the system functions, 58 00:04:39,820 --> 00:04:41,300 all the different zones. 59 00:04:44,300 --> 00:04:47,780 The scalloped reef edge where you see all the dynamic forces, the wave 60 00:04:47,780 --> 00:04:51,940 actions coming in, the wash moving through, all the new nutrients 61 00:04:51,940 --> 00:04:53,820 coming into the reef system. 62 00:04:59,700 --> 00:05:02,660 And then you move into the shallow reef flat areas where certain types 63 00:05:02,660 --> 00:05:06,300 of corals are specialised in coping with these extreme environments. 64 00:05:12,540 --> 00:05:15,820 My favourite part of the reef is actually the lagoon where you get 65 00:05:15,820 --> 00:05:20,060 all of these complex reef systems forming a patchwork layer. 66 00:05:20,060 --> 00:05:22,060 It's like a mosaic system. 67 00:05:24,140 --> 00:05:26,980 The incredible colours that are coming from the reefs, 68 00:05:26,980 --> 00:05:30,500 just this azure blue and turquoise colours. 69 00:05:30,500 --> 00:05:33,340 And every time I see those, it does something to me personally. 70 00:05:33,340 --> 00:05:35,660 It makes the hairs on the back of my neck stand up. 71 00:05:35,660 --> 00:05:37,940 I just react to that colour. 72 00:05:37,940 --> 00:05:40,780 And, for me, it's kind of like a spiritual home 73 00:05:40,780 --> 00:05:42,340 for the marine world. 74 00:05:50,020 --> 00:05:54,820 There's no other systems on our planet, anything like this. 75 00:05:54,820 --> 00:05:58,660 It's just a spectacular environment, so visually beautiful, 76 00:05:58,660 --> 00:06:02,060 so ecologically complex and so amazingly fragile. 77 00:06:14,700 --> 00:06:17,340 I wish everyone on the planet could come and see a healthy, 78 00:06:17,340 --> 00:06:20,380 functioning reef system, and hopefully in the future 79 00:06:20,380 --> 00:06:23,220 there will still be enough so that people can enjoy them. 80 00:06:27,180 --> 00:06:28,940 Back on the ground below, 81 00:06:28,940 --> 00:06:33,140 summer is in full swing and Heron Island is at its busiest. 82 00:06:34,620 --> 00:06:39,140 It's only 800 metres long, but the dense forest canopy offers 83 00:06:39,140 --> 00:06:42,540 prime real estate for those looking to nest. 84 00:06:42,540 --> 00:06:47,380 From December to March each year, the wildlife here is booming. 85 00:06:48,820 --> 00:06:54,100 There's no better time to meet the residents of this tropical oasis. 86 00:06:54,100 --> 00:06:59,380 Every inch of the forest is occupied with over 100,000 birds working 87 00:06:59,380 --> 00:07:01,380 tirelessly to raise their young. 88 00:07:07,940 --> 00:07:11,980 The white sandy beaches that encircle the island are home 89 00:07:11,980 --> 00:07:14,580 to a busy green sea turtle nursery. 90 00:07:20,300 --> 00:07:22,740 Heron Island is at the centre of a reef 91 00:07:22,740 --> 00:07:27,140 over 100 times larger than the island itself, which is full 92 00:07:27,140 --> 00:07:29,420 of charismatic creatures. 93 00:07:29,420 --> 00:07:32,260 An extraordinary number of fish 94 00:07:32,260 --> 00:07:34,700 and 18 species of rays and sharks 95 00:07:34,700 --> 00:07:36,340 call these waters home. 96 00:07:43,660 --> 00:07:47,500 But it's the towering corals that provide food and shelter 97 00:07:47,500 --> 00:07:49,540 for such an abundance of life. 98 00:08:00,940 --> 00:08:05,460 Each day, this magical place springs to life, 99 00:08:05,460 --> 00:08:08,340 as every animal within this underwater wonderland 100 00:08:08,340 --> 00:08:09,740 has a role to play. 101 00:08:19,420 --> 00:08:22,860 Damselfish stand guard over their coral gardens. 102 00:08:25,180 --> 00:08:29,340 And this bubble-tip anemone provides a safe home for clownfish. 103 00:08:40,300 --> 00:08:43,460 Whilst larger reef residents patrol for food. 104 00:08:57,020 --> 00:09:02,100 One of the busiest parts of the reef is the cleaning station. 105 00:09:02,100 --> 00:09:05,260 Marine creatures will pass through here whenever they need some 106 00:09:05,260 --> 00:09:06,940 attention from a cleaner fish. 107 00:09:08,940 --> 00:09:11,620 A green sea turtle arrives to take 108 00:09:11,620 --> 00:09:13,820 a well-earned rest from its travels. 109 00:09:20,340 --> 00:09:24,620 By raising its head and stretching out its flippers, this turtle shows 110 00:09:24,620 --> 00:09:27,060 it's ready for a once-over. 111 00:09:27,060 --> 00:09:31,020 Its shell is so sensitive it can feel every nibble. 112 00:09:41,900 --> 00:09:45,700 Every animal here helps to keep the reef and its residents 113 00:09:45,700 --> 00:09:47,140 clean and healthy. 114 00:09:49,220 --> 00:09:52,420 With such an abundance of marine life, Heron Reef 115 00:09:52,420 --> 00:09:54,060 is relatively pristine. 116 00:09:55,700 --> 00:09:59,380 But sadly, this place is the exception to the rule. 117 00:09:59,380 --> 00:10:02,780 As across the globe, coral reefs are struggling. 118 00:10:04,020 --> 00:10:08,300 Coral reefs are an essential part of our life support system. 119 00:10:08,300 --> 00:10:12,580 Unfortunately, over the past 30 years, we've lost a lot of corals 120 00:10:12,580 --> 00:10:14,980 and it's been a combination of problems - 121 00:10:14,980 --> 00:10:16,620 pollution, overfishing 122 00:10:16,620 --> 00:10:19,020 and, of course, nowadays we have the threat 123 00:10:19,020 --> 00:10:21,420 of major climate change. 124 00:10:21,420 --> 00:10:23,940 Director of The Global Change Institute, 125 00:10:23,940 --> 00:10:26,980 Professor Ove Hoegh-Guldberg, is a world expert 126 00:10:26,980 --> 00:10:29,420 on climate change and coral reefs. 127 00:10:29,420 --> 00:10:32,700 Climate change impacts coral reefs in a number of ways. 128 00:10:32,700 --> 00:10:35,660 As we are adding carbon dioxide to the atmosphere 129 00:10:35,660 --> 00:10:37,500 that then drives the temperature up, 130 00:10:37,500 --> 00:10:39,340 and it doesn't matter whether you're on land 131 00:10:39,340 --> 00:10:41,460 or in the upper layers of the ocean, 132 00:10:41,460 --> 00:10:44,540 that's enough to cause problems with coral reefs. 133 00:10:44,540 --> 00:10:47,660 If we see coral reefs die and other parts of the ocean die, 134 00:10:47,660 --> 00:10:51,780 we will start to threaten our very own existence. 135 00:10:51,780 --> 00:10:56,180 Ove first came to Heron Island when he was 18 years old, and now, 136 00:10:56,180 --> 00:10:59,300 along with the team at the research station, is leading the way 137 00:10:59,300 --> 00:11:02,700 in understanding what the future holds for all life found 138 00:11:02,700 --> 00:11:04,260 on coral reefs. 139 00:11:04,260 --> 00:11:08,420 We've been coming to Heron Island for three or four decades now, 140 00:11:08,420 --> 00:11:13,300 and because it's near pristine, we really have a unique opportunity, 141 00:11:13,300 --> 00:11:16,940 together with the facilities that the university provides, to get 142 00:11:16,940 --> 00:11:19,420 at some really important questions. 143 00:11:27,100 --> 00:11:31,260 Run by the University of Queensland, Heron Island Research Station 144 00:11:31,260 --> 00:11:35,260 carries out ground-breaking work using the latest technologies 145 00:11:35,260 --> 00:11:38,300 to explore the inner workings of reefs. 146 00:11:38,300 --> 00:11:42,700 The ability to have access to advanced laboratory tools, 147 00:11:42,700 --> 00:11:44,420 cameras and so on, 148 00:11:44,420 --> 00:11:48,100 it's really generating enormous amounts of interest and research 149 00:11:48,100 --> 00:11:49,220 and so on. 150 00:11:51,500 --> 00:11:55,700 This work equips organisations and governments with the information 151 00:11:55,700 --> 00:11:58,140 they need to protect coral reefs. 152 00:12:00,700 --> 00:12:04,660 Scientists here study everything the island has to offer, 153 00:12:04,660 --> 00:12:08,180 from the colourful corals that are the foundations of all life 154 00:12:08,180 --> 00:12:12,580 here to the feathered families that arrive each year to breed. 155 00:12:16,460 --> 00:12:20,140 And, as December dawns, one of the reef's most charismatic 156 00:12:20,140 --> 00:12:24,500 residents comes to shore to nest, offering researchers an unrivalled 157 00:12:24,500 --> 00:12:27,820 chance to get a closer look at these ancient mariners. 158 00:12:32,620 --> 00:12:36,540 Green sea turtles have been monitored on Heron Island for almost 159 00:12:36,540 --> 00:12:37,780 50 years. 160 00:12:40,860 --> 00:12:44,740 For turtle biologist Janine Ferguson and her team, 161 00:12:44,740 --> 00:12:47,380 it's like old friends coming home. 162 00:12:47,380 --> 00:12:49,900 I love it. Been involved with the turtles here since 163 00:12:49,900 --> 00:12:55,300 about 1987, but I'm not sure what it is about sea turtles 164 00:12:55,300 --> 00:12:58,420 that grabs a lot of people's attention and they just do fall 165 00:12:58,420 --> 00:12:59,540 in love with them. 166 00:12:59,540 --> 00:13:03,500 During the nesting season, as night begins to fall, 167 00:13:03,500 --> 00:13:07,860 females patrol the beaches, looking for a spot to lay their eggs. 168 00:13:07,860 --> 00:13:12,900 They haul themselves up and out of the water, a herculean effort. 169 00:13:15,180 --> 00:13:18,380 What she is looking for is a position that's high enough 170 00:13:18,380 --> 00:13:19,700 above the high-water mark 171 00:13:19,700 --> 00:13:22,020 so that her eggs are in a safe place 172 00:13:22,020 --> 00:13:25,300 and will not get inundated with any water from high tides 173 00:13:25,300 --> 00:13:27,700 or a tidal surge from a cyclone. 174 00:13:28,940 --> 00:13:32,980 The turtle digs a hole around 60 centimetres deep. 175 00:13:32,980 --> 00:13:36,900 She's using her front flippers to actually get rid of that sand, 176 00:13:36,900 --> 00:13:38,540 the more drier sand, 177 00:13:38,540 --> 00:13:41,380 and she'll also use her rear flippers as well, to flick the sand 178 00:13:41,380 --> 00:13:43,820 backwards away from where she actually wants to dig 179 00:13:43,820 --> 00:13:45,140 that egg chamber. 180 00:13:51,100 --> 00:13:53,540 They spend a lot of time up there, getting rid of that 181 00:13:53,540 --> 00:13:55,060 soft sand from around them. 182 00:14:02,500 --> 00:14:05,500 The bone structure within their rear flippers is very similar 183 00:14:05,500 --> 00:14:07,180 to our hand. 184 00:14:07,180 --> 00:14:11,700 She can actually cup it and bring it up and out of the egg chamber 185 00:14:11,700 --> 00:14:14,660 and then reach in with her other flipper and bring out another 186 00:14:14,660 --> 00:14:17,420 flipper full of sand and put it beside her. 187 00:14:17,420 --> 00:14:19,140 It's in sort of a bowl shape. 188 00:14:20,580 --> 00:14:23,820 And she needs to get that specific shape so that she can actually 189 00:14:23,820 --> 00:14:27,300 then put her eggs into that, what we call the egg chamber. 190 00:14:27,300 --> 00:14:33,340 It can take up to five hours of hard work for her to lay over 100 eggs. 191 00:14:33,340 --> 00:14:36,820 She is more committed to putting those eggs into the ground. 192 00:14:36,820 --> 00:14:40,500 So she's a lot more accepting of us being around her. 193 00:14:40,500 --> 00:14:44,700 She's actually filling in her egg chamber and she's just using 194 00:14:44,700 --> 00:14:48,420 her rear flippers again just to cover those eggs 195 00:14:48,420 --> 00:14:51,700 up into a nice little secure area. 196 00:14:51,700 --> 00:14:54,700 Once she's finished laying her eggs, Janine can move 197 00:14:54,700 --> 00:14:56,500 in to attach an ID tag. 198 00:14:57,780 --> 00:15:03,060 The project itself has been going since 1974, and most of our females 199 00:15:03,060 --> 00:15:05,900 during that period of time should be tagged. 200 00:15:05,900 --> 00:15:09,780 So if we don't have a tag on this girl, it probably means 201 00:15:09,780 --> 00:15:13,380 that this is her first laying season. 202 00:15:13,380 --> 00:15:17,660 Since Janine and her team started monitoring Heron's turtles 203 00:15:17,660 --> 00:15:20,300 their numbers have more than doubled. 204 00:15:20,300 --> 00:15:23,980 A great sign that this population is doing well. 205 00:15:23,980 --> 00:15:27,420 But the impact rising temperatures will have on this species 206 00:15:27,420 --> 00:15:29,260 is not well understood. 207 00:15:29,260 --> 00:15:33,700 So this long-term monitoring work is more important than ever. 208 00:15:35,700 --> 00:15:38,740 This turtle mother's task is over. 209 00:15:38,740 --> 00:15:40,660 She heads back towards the water. 210 00:15:49,860 --> 00:15:54,500 There are plenty of opportunities on the reef around Heron Island 211 00:15:54,500 --> 00:15:57,500 for hungry turtles to replenish their food stores. 212 00:16:07,500 --> 00:16:11,460 They gather around an old shipwreck, feasting on a treat brought 213 00:16:11,460 --> 00:16:12,740 in by a high tide. 214 00:16:43,180 --> 00:16:47,820 Small, jelly-like creatures called salps, a type of plankton, 215 00:16:47,820 --> 00:16:50,300 are carried here by the current, 216 00:16:50,300 --> 00:16:53,700 and they make for a nutritious meal on the move. 217 00:17:20,340 --> 00:17:25,380 But these magnificent turtles also help the reef in return, in ways 218 00:17:25,380 --> 00:17:27,820 we're only beginning to comprehend. 219 00:17:32,060 --> 00:17:36,180 Green turtles can often be found perusing the underwater gardens, 220 00:17:36,180 --> 00:17:38,180 which neighbour coral reefs. 221 00:17:39,420 --> 00:17:41,260 These are filled with the ocean's 222 00:17:41,260 --> 00:17:44,300 only flowering plants, seagrass. 223 00:17:50,780 --> 00:17:53,820 Seagrass meadows can store ten times 224 00:17:53,820 --> 00:17:58,740 as much carbon dioxide as the same area of rainforest, 225 00:17:58,740 --> 00:18:02,460 and regular mowing keeps them in good condition. 226 00:18:20,300 --> 00:18:24,700 Consuming up to four kilos of seagrass a day, a turtle 227 00:18:24,700 --> 00:18:27,780 will graze the same patch for several months before moving on. 228 00:18:41,780 --> 00:18:44,220 But like any terrestrial prairie, 229 00:18:44,220 --> 00:18:47,900 seagrass meadows also attract herds of giant grazers. 230 00:18:50,820 --> 00:18:51,780 Dugongs... 231 00:18:53,380 --> 00:18:56,500 ..one of the largest herbivores in the ocean. 232 00:18:58,860 --> 00:19:03,500 There are more dugongs in Australia than any other place on Earth. 233 00:19:08,020 --> 00:19:12,260 A distant relative of the elephant, they can reach three metres 234 00:19:12,260 --> 00:19:14,540 in length and weigh half a tonne. 235 00:19:17,060 --> 00:19:20,180 And they eat almost nothing but seagrass. 236 00:19:25,860 --> 00:19:30,540 These regular grazers play an essential role, spreading seagrass 237 00:19:30,540 --> 00:19:31,940 seeds far and wide. 238 00:19:41,540 --> 00:19:46,220 And importantly for coral reefs, seagrass meadows provide safe 239 00:19:46,220 --> 00:19:48,460 nursery grounds for young fish. 240 00:19:55,060 --> 00:19:58,580 Fish that are still too small to cope with the hustle and bustle 241 00:19:58,580 --> 00:20:00,220 of reef life 242 00:20:00,220 --> 00:20:04,460 but who will one day grow up to join this extravagant world. 243 00:20:07,380 --> 00:20:10,940 Fish found on the reef are reliant on the healthy appetites 244 00:20:10,940 --> 00:20:12,700 of dugongs and turtles. 245 00:20:14,660 --> 00:20:18,380 It's these interconnected relationships that underpin 246 00:20:18,380 --> 00:20:21,340 the foundations of the Great Barrier Reef. 247 00:20:23,380 --> 00:20:27,620 And perhaps the most important one of all involves the corals 248 00:20:27,620 --> 00:20:32,900 themselves as they harness up to 90% of their energy from microscopic 249 00:20:32,900 --> 00:20:35,260 algae living within their cells. 250 00:20:37,060 --> 00:20:41,660 Only with this help can they build such impressive reefs. 251 00:20:41,660 --> 00:20:44,860 It's a relationship that's vital to everything that calls 252 00:20:44,860 --> 00:20:46,740 this natural wonder home. 253 00:20:48,340 --> 00:20:51,780 But in recent years, it's come under increasing pressure 254 00:20:51,780 --> 00:20:54,620 as our planet faces a climate crisis. 255 00:20:56,660 --> 00:20:58,260 Our seas are warming. 256 00:21:01,020 --> 00:21:05,460 And a rise in temperature of just two degrees for a month 257 00:21:05,460 --> 00:21:09,860 can be enough to cause the coral polyps to eject their algae. 258 00:21:16,140 --> 00:21:20,380 When this happens, the corals fade, losing both their colour 259 00:21:20,380 --> 00:21:22,380 and their main food supply. 260 00:21:31,420 --> 00:21:36,260 If high temperatures are sustained, corals bleached in this way 261 00:21:36,260 --> 00:21:37,620 are likely to die. 262 00:21:45,460 --> 00:21:49,860 Since 2016, half of the Great Barrier Reef's shallow water 263 00:21:49,860 --> 00:21:53,540 corals have perished due to bleaching. 264 00:21:53,540 --> 00:21:58,460 If we don't change our habits with regards to CO2 emissions, 265 00:21:58,460 --> 00:22:01,260 I do not believe it's possible that coral reefs will be here 266 00:22:01,260 --> 00:22:02,340 in the future. 267 00:22:03,340 --> 00:22:06,140 On Heron Island, Professor Sophie Dove 268 00:22:06,140 --> 00:22:08,180 is in a race against time, 269 00:22:08,180 --> 00:22:13,260 trying to predict what the future may look like for coral reefs. 270 00:22:13,260 --> 00:22:16,100 By creating miniature reefs in a set of tanks, 271 00:22:16,100 --> 00:22:20,580 she can find out how corals might react to future climate conditions. 272 00:22:22,420 --> 00:22:27,340 The aim is to reproduce a structure that looks a little bit at least 273 00:22:27,340 --> 00:22:29,900 what we have out there on the reef slope 274 00:22:29,900 --> 00:22:32,180 so that we can then examine 275 00:22:32,180 --> 00:22:35,820 what increases in temperature and acidification 276 00:22:35,820 --> 00:22:37,700 do to the mini reefs. 277 00:22:39,740 --> 00:22:42,260 We put them and we weigh them underwater. 278 00:22:44,340 --> 00:22:50,140 We do a lot of 3D scanning now and so they give us volumetric change 279 00:22:50,140 --> 00:22:53,460 and also the change over the surface area of the coral. 280 00:22:55,100 --> 00:22:58,540 And those are fundamental to understanding 281 00:22:58,540 --> 00:23:03,660 whether it is possible to generate corals that can grow and survive 282 00:23:03,660 --> 00:23:07,500 the type of environments that we're going to have in the future. 283 00:23:07,500 --> 00:23:12,140 Sophie's experiments have shown that if temperatures continue to rise 284 00:23:12,140 --> 00:23:15,820 at their current rate, we will lose our coral reefs 285 00:23:15,820 --> 00:23:17,620 in just 30 years. 286 00:23:17,620 --> 00:23:19,340 They literally disintegrate. 287 00:23:19,340 --> 00:23:23,940 They start off as these lovely 3-D tiered structures 288 00:23:23,940 --> 00:23:30,140 and they collapse in to this 2-D scuzz of cyanobacteria. 289 00:23:31,660 --> 00:23:33,900 The situation is desperate. 290 00:23:35,340 --> 00:23:40,780 But scientists are doing their best to bide coral reefs more time. 291 00:23:40,780 --> 00:23:44,700 And the way that corals reproduce is providing a much-needed 292 00:23:44,700 --> 00:23:45,860 glimmer of hope. 293 00:23:47,940 --> 00:23:50,340 Coral expert Professor Peter Harrison 294 00:23:50,340 --> 00:23:53,300 has travelled to the northern Great Barrier Reef 295 00:23:53,300 --> 00:23:56,900 with a ground-breaking idea that could offer reefs a lifeline. 296 00:23:58,660 --> 00:24:00,660 Coral IVF. 297 00:24:00,660 --> 00:24:02,900 Collecting eggs and sperm from corals 298 00:24:02,900 --> 00:24:05,180 that have survived mass bleaching 299 00:24:05,180 --> 00:24:08,540 and transferring them to recolonise dead reefs. 300 00:24:15,100 --> 00:24:17,900 For this to work, he's searching for live coral 301 00:24:17,900 --> 00:24:20,020 that's healthy enough to spawn. 302 00:24:24,460 --> 00:24:27,100 But these corals release eggs and sperm 303 00:24:27,100 --> 00:24:29,740 on just a few nights each year, 304 00:24:29,740 --> 00:24:31,780 so there is no margin for error. 305 00:24:34,660 --> 00:24:37,700 There's good coral cover, really good diversity, 306 00:24:37,700 --> 00:24:40,300 lots of survivors from the recent bleaching events. 307 00:24:40,300 --> 00:24:42,740 We need to capture these eggs and sperm now 308 00:24:42,740 --> 00:24:44,540 before the next bleaching event 309 00:24:44,540 --> 00:24:47,940 because we can't be absolutely sure that these corals will survive 310 00:24:47,940 --> 00:24:49,660 the coming bleaching. 311 00:24:49,660 --> 00:24:51,780 With a site identified, 312 00:24:51,780 --> 00:24:56,180 the team can deploy the 65-metre spawn catcher, 313 00:24:56,180 --> 00:24:58,700 a giant ring of floats that will corral 314 00:24:58,700 --> 00:25:00,620 the released eggs and sperm 315 00:25:00,620 --> 00:25:03,460 into a fine net where it can be collected. 316 00:25:05,940 --> 00:25:08,900 But as night falls, the weather turns. 317 00:25:08,900 --> 00:25:11,220 It's always a bit of a worry when the wind blows up, 318 00:25:11,220 --> 00:25:14,060 and particularly as the wind is coming from the wrong direction. 319 00:25:14,060 --> 00:25:17,060 We're having to use a more exposed site. 320 00:25:17,060 --> 00:25:20,140 The window of opportunity is shrinking fast. 321 00:25:21,780 --> 00:25:24,740 And because artificial light affects the spawning, 322 00:25:24,740 --> 00:25:27,860 the team prepare to work in virtual darkness. 323 00:25:30,980 --> 00:25:32,820 It's a race against time. 324 00:25:33,940 --> 00:25:35,980 Our dive teams are in the water 325 00:25:35,980 --> 00:25:40,220 and now our job is to start looking for surface slicks 326 00:25:40,220 --> 00:25:44,100 as they start to develop before the wind picks up, 327 00:25:44,100 --> 00:25:46,340 because if we can get even a little bit of it 328 00:25:46,340 --> 00:25:48,380 in these spawn catcher nets, 329 00:25:48,380 --> 00:25:51,220 then we're looking good over the next few days. 330 00:25:51,220 --> 00:25:53,020 As long as we can stay on the water... 331 00:25:53,020 --> 00:25:54,540 CLAP OF THUNDER 332 00:25:54,540 --> 00:25:57,140 ..because that was a big lightning strike. 333 00:25:57,140 --> 00:26:00,540 Small boats are one of the most dangerous places to be 334 00:26:00,540 --> 00:26:02,020 in a lightning storm. 335 00:26:02,020 --> 00:26:05,420 Peter and the team might be battling the weather on the surface, 336 00:26:05,420 --> 00:26:07,660 but their timing is perfect. 337 00:26:09,460 --> 00:26:13,140 Beneath them, the coral is putting on a dazzling display. 338 00:26:14,500 --> 00:26:18,940 Millions of individual corals are releasing their eggs and sperm 339 00:26:18,940 --> 00:26:21,420 at exactly the same time. 340 00:26:21,420 --> 00:26:24,380 This extraordinary natural phenomenon 341 00:26:24,380 --> 00:26:26,820 is happening right on cue. 342 00:26:26,820 --> 00:26:29,820 For more than 1,000 kilometres over the Great Barrier Reef, 343 00:26:29,820 --> 00:26:33,060 you'll see synchronous spawning of many of these same species. 344 00:26:39,140 --> 00:26:43,500 The team work deep into the night to collect as much as possible. 345 00:26:43,500 --> 00:26:46,860 By the time they're finished, it's 3:30 in the morning. 346 00:26:48,460 --> 00:26:54,100 Overnight, the spawn is transported 21 miles north to Vlasoff Reef. 347 00:26:55,220 --> 00:27:00,060 Just 18 months ago, Vlasoff was full of life and colour. 348 00:27:00,060 --> 00:27:03,100 But today, it's a dead, white expanse. 349 00:27:04,620 --> 00:27:08,780 Peter's team have built floating pools above this reef 350 00:27:08,780 --> 00:27:11,740 where the microscopic larvae will mature. 351 00:27:11,740 --> 00:27:14,900 In time, they will be released to form new colonies 352 00:27:14,900 --> 00:27:17,460 on the dead skeleton below. 353 00:27:17,460 --> 00:27:22,060 In just three years, the new corals should be ready to breed. 354 00:27:22,060 --> 00:27:24,260 It's a complex operation. 355 00:27:24,260 --> 00:27:26,900 We've got a lot of healthy embryos in the cultures 356 00:27:26,900 --> 00:27:29,820 and it looks like we're going to be successful in at least getting 357 00:27:29,820 --> 00:27:32,260 through the second stage of rearing the larvae. 358 00:27:34,420 --> 00:27:35,860 We've still got a way to go 359 00:27:35,860 --> 00:27:39,660 but, so far, I'm really happy and increasingly confident 360 00:27:39,660 --> 00:27:41,900 that we will get a good result. 361 00:27:48,860 --> 00:27:51,460 Peter's ground-breaking coral IVF 362 00:27:51,460 --> 00:27:56,300 is able to speed up the growth and recovery of damaged coral reefs. 363 00:27:58,620 --> 00:28:02,140 But the health of these reefs is not only influenced by life 364 00:28:02,140 --> 00:28:03,420 beneath the waves. 365 00:28:04,860 --> 00:28:08,700 Recent research has shown that life on land is more connected to coral 366 00:28:08,700 --> 00:28:11,260 reefs than we ever thought possible. 367 00:28:14,300 --> 00:28:18,060 On Heron Island, the birds are busy looking after their young. 368 00:28:30,540 --> 00:28:34,660 It's now January, and in burrows below the forest's trees 369 00:28:34,660 --> 00:28:39,500 13,000 wedge-tailed shearwaters are incubating their eggs. 370 00:28:39,500 --> 00:28:40,860 During the day, 371 00:28:40,860 --> 00:28:44,900 it's hard to know they're here as they keep below ground. 372 00:28:44,900 --> 00:28:48,580 But by using burrow cameras, Abbie Taylor and the team 373 00:28:48,580 --> 00:28:52,180 at Heron Island Research Station can get a unique insight 374 00:28:52,180 --> 00:28:53,420 into their lives. 375 00:28:58,020 --> 00:29:01,540 The shearwaters have travelled all the way from Micronesia, 376 00:29:01,540 --> 00:29:04,340 nearly 4,000 miles away, to nest here. 377 00:29:07,740 --> 00:29:12,300 This shearwater mum, called Winona, got off to a rather bad start. 378 00:29:18,060 --> 00:29:20,900 Winona is a little bit of a special story to us. 379 00:29:20,900 --> 00:29:23,700 She was a bird that was rescued out of a skip bin, 380 00:29:23,700 --> 00:29:26,940 that was placed in a nest, just to give her a little bit of a rest, 381 00:29:26,940 --> 00:29:29,060 and she happened to lay an egg in the first 24 hours 382 00:29:29,060 --> 00:29:30,180 of being in the nest. 383 00:29:30,180 --> 00:29:33,060 So we knew exactly when her egg was laid, which was great, 384 00:29:33,060 --> 00:29:35,820 because we could predict when it was going to hatch. 385 00:29:35,820 --> 00:29:40,140 Over a month has passed and her chick, named Willie, is almost 386 00:29:40,140 --> 00:29:42,220 ready to hatch. 387 00:29:42,220 --> 00:29:45,020 Winona, we're predicting, is a first-time mum. 388 00:29:45,020 --> 00:29:48,060 And she got a little bit scared when the egg started to vibrate 389 00:29:48,060 --> 00:29:51,500 when it was hatching and actually kicked it across the nest. 390 00:29:51,500 --> 00:29:52,900 And so it was pretty cool to see. 391 00:29:52,900 --> 00:29:54,380 It actually hit the back wall 392 00:29:54,380 --> 00:29:57,180 and you could hear Willie squawking inside the egg. 393 00:29:57,180 --> 00:30:00,420 SQUEAKING 394 00:30:09,180 --> 00:30:12,220 Being a shearwater parent is challenging. 395 00:30:12,220 --> 00:30:15,060 Growing chicks need a regular supply of food. 396 00:30:18,340 --> 00:30:21,380 So each morning, well before sunrise, 397 00:30:21,380 --> 00:30:24,340 they leave in search of the next meal. 398 00:30:24,340 --> 00:30:28,460 But here, in the dense forest, there is little room to fly. 399 00:30:30,260 --> 00:30:33,740 By walking along the forest's well-trodden footpath, 400 00:30:33,740 --> 00:30:37,300 they make their way towards the beach where there's easy access 401 00:30:37,300 --> 00:30:38,620 to the open ocean. 402 00:30:40,700 --> 00:30:44,340 They line up in clearings as if taxiing for takeoff... 403 00:30:48,420 --> 00:30:51,140 ..and, with a good run-up, head out to sea. 404 00:31:05,460 --> 00:31:09,900 These expert foragers will spend the entire day fishing at sea. 405 00:31:17,460 --> 00:31:21,140 One of the parents fishes close by to provide a regular supply 406 00:31:21,140 --> 00:31:22,700 of food for the chick. 407 00:31:28,180 --> 00:31:32,060 While the other will spend two weeks on the wing travelling up to 600 408 00:31:32,060 --> 00:31:34,700 miles to stock up on food for itself. 409 00:32:01,540 --> 00:32:04,780 The adults only return under cover of darkness. 410 00:32:09,180 --> 00:32:11,900 After a bumpy landing, they'll quickly head 411 00:32:11,900 --> 00:32:14,900 into their burrows to provide their chicks with a meal 412 00:32:14,900 --> 00:32:16,220 of fish and squid. 413 00:32:19,420 --> 00:32:24,100 Every couple of weeks, the parents will meet to swap shifts, 414 00:32:24,100 --> 00:32:27,220 using their haunting calls to find each other. 415 00:32:27,220 --> 00:32:31,980 When both parents come in, they are, um, I guess, super... 416 00:32:31,980 --> 00:32:33,620 'romantic' is a terrible word, 417 00:32:33,620 --> 00:32:36,860 but they are really affectionate towards each other and there is lots 418 00:32:36,860 --> 00:32:41,180 of nuzzling and preening of both parents and then the chick as well. 419 00:32:41,180 --> 00:32:43,620 So they will sit in a little kind of family huddle 420 00:32:43,620 --> 00:32:45,980 and, yeah, preen each other, which is very cute. 421 00:32:48,060 --> 00:32:51,500 Their reunion is brief, as the next morning both parents 422 00:32:51,500 --> 00:32:54,100 will go their separate ways to fish. 423 00:32:55,660 --> 00:32:58,500 It's these foraging trips that are the key 424 00:32:58,500 --> 00:33:00,180 to helping coral reefs. 425 00:33:01,820 --> 00:33:05,500 Every time they return to the island from their long-distance hunting 426 00:33:05,500 --> 00:33:08,940 trips, sea birds bring back essential nutrients in their 427 00:33:08,940 --> 00:33:13,140 droppings, or guano, which flow into the surrounding waters. 428 00:33:16,660 --> 00:33:20,300 These nutrients result in greater numbers of fish 429 00:33:20,300 --> 00:33:22,340 and healthier coral reefs... 430 00:33:24,940 --> 00:33:28,540 ..helping these precious ecosystems to thrive. 431 00:33:34,140 --> 00:33:37,780 Across our seas, ocean commuters carry nutrients 432 00:33:37,780 --> 00:33:39,420 for thousands of miles. 433 00:33:42,900 --> 00:33:46,340 And few more so than migrating whales, 434 00:33:46,340 --> 00:33:51,220 who spend their lives traversing the big blue. 435 00:33:51,220 --> 00:33:53,460 Humpback whales make their way 436 00:33:53,460 --> 00:33:57,100 from Antarctica to the Great Barrier Reef each year. 437 00:34:26,340 --> 00:34:29,180 They've travelled all the way here to breed. 438 00:34:29,180 --> 00:34:32,260 And these warm tropical waters provide a safe place 439 00:34:32,260 --> 00:34:37,300 for their calves to grow and fatten up before returning to cooler seas. 440 00:34:40,140 --> 00:34:43,860 But during the breeding season, some of the greatest migrations 441 00:34:43,860 --> 00:34:47,660 on the Great Barrier Reef are carried out by an animal 442 00:34:47,660 --> 00:34:49,500 just centimetres in size. 443 00:34:59,060 --> 00:35:03,100 Loggerhead turtle hatchlings from the Great Barrier Reef travel 444 00:35:03,100 --> 00:35:07,580 down the East Australian Current, past New Zealand, and all the way 445 00:35:07,580 --> 00:35:11,420 across the Pacific to Chile and Peru, a distance 446 00:35:11,420 --> 00:35:13,060 of over 8,000 miles. 447 00:35:14,500 --> 00:35:18,740 They won't arrive back until they're around 16 years of age. 448 00:35:23,460 --> 00:35:27,780 As adults, marine turtles will then establish home ranges 449 00:35:27,780 --> 00:35:30,940 travelling between feeding and nesting areas. 450 00:35:32,540 --> 00:35:37,220 Each year, in the northern Great Barrier Reef, tens of 451 00:35:37,220 --> 00:35:40,860 thousands of turtles gather near their natal breeding grounds. 452 00:35:44,700 --> 00:35:47,740 They spread out as far as the eye can see. 453 00:35:51,300 --> 00:35:56,060 And each turtle will carry little hitchhikers, parasites 454 00:35:56,060 --> 00:36:00,820 and barnacles, on their bodies, transporting them from open ocean 455 00:36:00,820 --> 00:36:02,660 to coral reefs - 456 00:36:02,660 --> 00:36:06,380 increasing the biodiversity of our blue planet. 457 00:36:09,140 --> 00:36:14,420 But as our influence on the ocean increases, these migrations are also 458 00:36:14,420 --> 00:36:17,420 exposing marine turtles to great dangers. 459 00:36:22,340 --> 00:36:26,180 It's thought 52% of sea turtles worldwide 460 00:36:26,180 --> 00:36:28,340 have ingested plastic debris. 461 00:36:31,300 --> 00:36:35,340 And over 1,000 die each year due to entanglement. 462 00:36:40,620 --> 00:36:44,900 Across the world, marine turtle populations are struggling. 463 00:36:46,900 --> 00:36:49,140 But there are people trying to help. 464 00:36:51,780 --> 00:36:54,260 In the northern Great Barrier Reef, 465 00:36:54,260 --> 00:36:59,340 the Cairns Turtle Rehabilitation Centre, run by Jennie Gilbert, works 466 00:36:59,340 --> 00:37:03,780 to get sick and injured turtles back into the wild. 467 00:37:03,780 --> 00:37:06,460 One of the current residents is this female, 468 00:37:06,460 --> 00:37:10,300 who was hit by a boat after ingesting some fishing line. 469 00:37:10,300 --> 00:37:13,340 It's not only done enormous amounts of damage to her shell, 470 00:37:13,340 --> 00:37:15,940 but we're going to have to amputate that back flipper 471 00:37:15,940 --> 00:37:19,100 because the propeller went through and she's got nerve damage. 472 00:37:19,100 --> 00:37:21,060 It's completely overwhelming, isn't it? 473 00:37:21,060 --> 00:37:26,100 Just... She is a case study in what we are doing to our oceans. 474 00:37:27,740 --> 00:37:31,620 Whether through entanglement or ingestion, plastics are clearly 475 00:37:31,620 --> 00:37:34,980 having a major impact on turtle populations. 476 00:37:34,980 --> 00:37:38,260 So this rescue and rehabilitation effort is more essential 477 00:37:38,260 --> 00:37:39,700 than ever before. 478 00:37:40,780 --> 00:37:46,220 At Cairns Aquarium is a very special green sea turtle called Midori. 479 00:37:46,220 --> 00:37:50,700 She was brought in two and a half years ago with tumours and plastics 480 00:37:50,700 --> 00:37:52,740 blocking her bowels. 481 00:37:52,740 --> 00:37:56,460 But now she's testament to the team's hard work and dedication. 482 00:37:56,460 --> 00:37:58,260 Isn't she beautiful? 483 00:37:58,260 --> 00:38:00,580 She looks in great shape, Jennie. She really does. 484 00:38:00,580 --> 00:38:03,020 She's in such good shape, she needs to go. 485 00:38:03,020 --> 00:38:04,820 Before Midori is released 486 00:38:04,820 --> 00:38:08,660 she needs a thorough checkup to make sure she's fit enough. 487 00:38:08,660 --> 00:38:11,780 For this, Jennie and the team have access to state-of-the-art 488 00:38:11,780 --> 00:38:14,860 medical equipment at the local hospital. 489 00:38:14,860 --> 00:38:17,980 A CT scan will reveal if she's free from tumours 490 00:38:17,980 --> 00:38:19,620 and plastic. 491 00:38:19,620 --> 00:38:22,780 So, Jennie, what are your thoughts looking at the scan? 492 00:38:22,780 --> 00:38:24,540 I can't see any obvious tumours. 493 00:38:24,540 --> 00:38:26,620 And also, we haven't picked up any plastic. 494 00:38:26,620 --> 00:38:29,900 So no tumours, no plastic. 495 00:38:29,900 --> 00:38:33,580 Is she ready to go? She's healthy and she's right to go. 496 00:38:33,580 --> 00:38:36,580 This magnificent turtle has the all clear. 497 00:38:38,020 --> 00:38:42,060 The next task is to fit Midori with a GPS tracker so the team 498 00:38:42,060 --> 00:38:45,020 can monitor her after her release. 499 00:38:45,020 --> 00:38:47,940 As much as we're aware that their carpuses 500 00:38:47,940 --> 00:38:49,980 are incredibly sensitive. 501 00:38:49,980 --> 00:38:54,100 Apparently, this beautiful female is re-assured 502 00:38:54,100 --> 00:38:57,340 if we just scratch it a little bit and pat it. 503 00:38:57,340 --> 00:38:58,940 So that's the job I've got right now, 504 00:38:58,940 --> 00:39:02,900 just to try and calm her down a little bit before we attach the tag. 505 00:39:02,900 --> 00:39:06,020 And...it's quite the privilege. 506 00:39:10,140 --> 00:39:13,580 This is nontoxic, right? Nontoxic, yes. 507 00:39:13,580 --> 00:39:16,220 So what kind of data is this going to give you 508 00:39:16,220 --> 00:39:18,540 about Midori once she's out in the wild? 509 00:39:18,540 --> 00:39:19,980 A tracker that size is amazing. 510 00:39:19,980 --> 00:39:23,940 It gives us a top time, a bottom time, dive time, dive depth, 511 00:39:23,940 --> 00:39:26,540 water temperature, distance and salinity. 512 00:39:26,540 --> 00:39:28,340 All in there. All in that little thing? Yes. 513 00:39:28,340 --> 00:39:31,100 You know, the most important thing about releasing a turtle 514 00:39:31,100 --> 00:39:33,140 is that we want a health profile. 515 00:39:33,140 --> 00:39:37,500 So we want to know that this turtle is diving and staying down there 516 00:39:37,500 --> 00:39:41,580 and feeding, rather than doing short and shallow dives. 517 00:39:41,580 --> 00:39:45,700 With the tracker fitted, Midori is transported to a reef 15 miles 518 00:39:45,700 --> 00:39:46,900 off the coast. 519 00:39:50,580 --> 00:39:53,340 She's to be released from this permanent platform 520 00:39:53,340 --> 00:39:55,220 at the reef's edge. 521 00:39:55,220 --> 00:39:59,740 This enables us to get in the water with her and make sure she's stable 522 00:39:59,740 --> 00:40:01,980 and happy before we let her go. 523 00:40:03,460 --> 00:40:06,540 After two and a half years of rehabilitation, 524 00:40:06,540 --> 00:40:08,380 this is a crucial moment. 525 00:40:11,660 --> 00:40:15,860 OK. Ready. Step forward. Stepping forward. 526 00:40:15,860 --> 00:40:17,380 Here we go. She's ready to go. 527 00:40:17,380 --> 00:40:20,780 She's going this way. We're heading her that way. Go, go, go, go. 528 00:40:30,620 --> 00:40:32,700 Yeah! 529 00:40:39,700 --> 00:40:41,700 LAUGHTER 530 00:40:41,700 --> 00:40:44,940 How are you feeling? Fantastic. What a great release. 531 00:40:44,940 --> 00:40:46,620 She was amazing. So amazing. So amazing. 532 00:40:46,620 --> 00:40:49,420 You know, that's two and a half years in captivity 533 00:40:49,420 --> 00:40:51,860 and she's just gone...straight out. 534 00:40:59,860 --> 00:41:04,500 With every turtle successfully released back into the wild, 535 00:41:04,500 --> 00:41:07,860 the future of our coral reefs looks a little bit brighter. 536 00:41:12,500 --> 00:41:16,860 But wildlife here needs to be ready for every eventuality. 537 00:41:19,740 --> 00:41:23,980 In the waters around Heron Island, reef residents have adapted 538 00:41:23,980 --> 00:41:25,740 in extraordinary ways... 539 00:41:27,900 --> 00:41:30,260 ..to this ever-changing landscape. 540 00:41:32,700 --> 00:41:37,100 Twice a day, Heron Reef undergoes a dramatic transformation... 541 00:41:38,420 --> 00:41:41,900 ..as the tide turns and gallons of water drain away. 542 00:41:53,380 --> 00:41:57,260 As the water finally recedes, this epaulette shark 543 00:41:57,260 --> 00:41:59,100 is left high and dry. 544 00:42:18,580 --> 00:42:20,820 No shark can breathe in air. 545 00:42:22,100 --> 00:42:25,300 But this fish out of water has a trick. 546 00:42:30,020 --> 00:42:33,860 By shutting down parts of its brain 547 00:42:33,860 --> 00:42:36,780 it can cope without oxygen for an hour. 548 00:42:44,580 --> 00:42:49,140 And, if necessary, it switches to survival strategy number two. 549 00:42:53,140 --> 00:42:56,180 This is a shark that can walk. 550 00:42:56,180 --> 00:42:59,220 As it searches for a refuge of water, 551 00:42:59,220 --> 00:43:01,220 it uses its fins as legs... 552 00:43:11,060 --> 00:43:13,060 ..until it reaches the sea. 553 00:43:20,380 --> 00:43:24,940 The epaulette shark is supremely adapted to life in the shallows. 554 00:43:26,980 --> 00:43:30,780 But in deeper waters, other weird and wonderful species 555 00:43:30,780 --> 00:43:33,860 have evolved their own unique strategies for survival. 556 00:43:35,940 --> 00:43:37,420 A Spanish dancer. 557 00:43:38,540 --> 00:43:42,900 This otherworldly creature is in fact a swimming sea slug. 558 00:43:43,940 --> 00:43:48,020 It spends most of its life on the sea floor, 559 00:43:48,020 --> 00:43:50,860 but by using flamenco-style movements, 560 00:43:50,860 --> 00:43:53,980 it glides through the water from one patch 561 00:43:53,980 --> 00:43:56,980 of reef to another to escape any threats. 562 00:43:58,580 --> 00:44:02,420 And its bright colours warns predators that it would make 563 00:44:02,420 --> 00:44:04,100 an unsavoury meal. 564 00:44:07,020 --> 00:44:11,940 On the seabed below, a tuskfish is presented with a problem. 565 00:44:14,420 --> 00:44:18,660 It spends each day foraging for clams, but these shells 566 00:44:18,660 --> 00:44:20,300 are difficult to open. 567 00:44:21,420 --> 00:44:26,020 Ingeniously, the tusk fish has a few tools under its belt. 568 00:44:29,540 --> 00:44:32,900 Its protruding teeth make excellent clamps 569 00:44:32,900 --> 00:44:36,860 and this mooring could provide the perfect workbench. 570 00:44:39,580 --> 00:44:41,780 It doesn't seem to be working. 571 00:44:43,260 --> 00:44:46,740 He takes a break for a mouth clean courtesy of a wrasse 572 00:44:46,740 --> 00:44:48,740 before starting round two. 573 00:45:03,780 --> 00:45:06,180 Will this brick prove to be more useful? 574 00:45:13,660 --> 00:45:15,540 Not this time. 575 00:45:18,900 --> 00:45:22,300 But it's clear that there is far more to these ocean 576 00:45:22,300 --> 00:45:24,820 creatures than first meets the eye. 577 00:45:27,620 --> 00:45:32,460 And this is never more apparent than at dawn, when coral reefs 578 00:45:32,460 --> 00:45:35,060 are filled with a chorus of sounds. 579 00:45:35,060 --> 00:45:39,100 ECHOES, CLICKS AND WHISTLES FROM MARINE LIFE 580 00:45:43,180 --> 00:45:46,900 These underwater cities are alive with conversation. 581 00:45:50,460 --> 00:45:53,820 On Heron Reef, one of the most talkative residents 582 00:45:53,820 --> 00:45:56,540 is the Barrier Reef clownfish. 583 00:45:56,540 --> 00:45:59,820 CLOWNFISH GRUNTS AND CLICKS 584 00:45:59,820 --> 00:46:03,660 This family have a convenient home within the tentacles 585 00:46:03,660 --> 00:46:05,500 of a bubble-tip anemone. 586 00:46:07,460 --> 00:46:11,220 The tentacles can kill, but by continuously rubbing 587 00:46:11,220 --> 00:46:15,620 against them, the clownfish can remain immune to their sting. 588 00:46:16,940 --> 00:46:21,180 Here they can shelter from danger and, in return, they help to keep 589 00:46:21,180 --> 00:46:22,580 the anemone clean. 590 00:46:23,820 --> 00:46:28,260 As with all clownfish, there is only one female present in this group 591 00:46:28,260 --> 00:46:31,340 and she rules over the rest. 592 00:46:31,340 --> 00:46:34,980 She's the largest amongst them and uses her size to chase 593 00:46:34,980 --> 00:46:36,380 off any intruders. 594 00:46:42,500 --> 00:46:46,420 The whole family communicates by popping and clicking, which helps 595 00:46:46,420 --> 00:46:48,980 to maintain ranks amongst the group 596 00:46:48,980 --> 00:46:53,620 and, when accompanied by some twitching, re-affirms a pair's bond. 597 00:46:57,540 --> 00:47:01,860 The noise of a coral reef is a key indication that the community 598 00:47:01,860 --> 00:47:03,260 is in good shape. 599 00:47:03,260 --> 00:47:06,420 In fact, the louder the community, the more inviting 600 00:47:06,420 --> 00:47:08,860 it is to newcomers. 601 00:47:08,860 --> 00:47:12,380 Deciphering this underwater language could be the secret 602 00:47:12,380 --> 00:47:14,060 to helping coral reefs. 603 00:47:19,660 --> 00:47:23,540 This little clownfish is no bigger than a button. 604 00:47:23,540 --> 00:47:27,980 But the time has come for it to find its place in the big city. 605 00:47:29,420 --> 00:47:33,740 At this stage in life, it may not be the best swimmer, but its hearing 606 00:47:33,740 --> 00:47:37,740 is so sensitive it can detect the presence of a reef over 100 607 00:47:37,740 --> 00:47:39,540 metres away. 608 00:47:40,940 --> 00:47:43,580 Exactly what sounds attract 609 00:47:43,580 --> 00:47:48,140 these tiny reef fish to a new home has so far evaded scientists. 610 00:47:49,700 --> 00:47:53,900 But on the outer edge of Heron Reef, Dr Steve Simpson and fellow 611 00:47:53,900 --> 00:47:58,260 biologist Tim Gordon are hoping to collect young reef fish to learn 612 00:47:58,260 --> 00:48:00,500 more about their acoustic world. 613 00:48:01,660 --> 00:48:05,580 It's here that juvenile reef fish will first arrive after spending 614 00:48:05,580 --> 00:48:08,020 several weeks at sea. 615 00:48:08,020 --> 00:48:10,540 They're swimming back towards coral reef environments. 616 00:48:10,540 --> 00:48:12,260 They're trying to find a place to make home. 617 00:48:12,260 --> 00:48:15,100 So if we take one of those fish, we can catch them in light traps. 618 00:48:16,540 --> 00:48:20,540 The baby reef fish will make their final approach in the dark 619 00:48:20,540 --> 00:48:24,260 to avoid predators and will be attracted to the bright lights 620 00:48:24,260 --> 00:48:25,420 of the trap. 621 00:48:44,940 --> 00:48:48,500 The next day, any fish that have been drawn in are ready 622 00:48:48,500 --> 00:48:50,380 for the team to retrieve. 623 00:49:06,740 --> 00:49:08,900 Right. So we've got a fish. Yes! Which is great. 624 00:49:08,900 --> 00:49:12,500 This is a peacock damselfish. That's large for the fish 625 00:49:12,500 --> 00:49:14,260 when they arrive on the reef. 626 00:49:14,260 --> 00:49:16,220 With this school of reef fish, 627 00:49:16,220 --> 00:49:18,380 they can begin their research. 628 00:49:25,340 --> 00:49:29,580 In the middle of the night, Steve and Tim set up a long plastic tube 629 00:49:29,580 --> 00:49:33,180 in shallow waters with speakers rigged at each end. 630 00:49:34,940 --> 00:49:38,900 OK. One of the fish is then transferred into the tube 631 00:49:38,900 --> 00:49:41,940 while speakers play different reef sounds. 632 00:49:43,060 --> 00:49:48,180 After a few moments to orientate itself, the fish clearly heads 633 00:49:48,180 --> 00:49:50,380 towards one of the speakers. 634 00:49:50,380 --> 00:49:53,420 By repeating this hundreds of times, 635 00:49:53,420 --> 00:49:56,740 the team can record which sounds are the most attractive 636 00:49:56,740 --> 00:49:59,100 to young reef fish. 637 00:49:59,100 --> 00:50:01,980 They really are attracted by that sound of snapping shrimp - 638 00:50:01,980 --> 00:50:03,980 the higher-frequency sounds that you could hear, 639 00:50:03,980 --> 00:50:05,300 those crackling sounds. 640 00:50:05,300 --> 00:50:07,620 And we think that that's because snapping shrimp live 641 00:50:07,620 --> 00:50:10,220 in the kind of rubbly areas on the edges of reefs, 642 00:50:10,220 --> 00:50:11,620 as do the baby fish. 643 00:50:11,620 --> 00:50:14,100 So we think snapping shrimp is a really good way of them finding 644 00:50:14,100 --> 00:50:16,020 the best possible place to live. 645 00:50:16,020 --> 00:50:19,540 The amazing thing, if we then play other sounds, then the larger fish 646 00:50:19,540 --> 00:50:21,620 start to show an interest. 647 00:50:21,620 --> 00:50:24,460 So we think that they can use snapping shrimp to find a good place 648 00:50:24,460 --> 00:50:25,700 to set up home. 649 00:50:25,700 --> 00:50:30,140 Once they're ready to graduate into the big fish community, 650 00:50:30,140 --> 00:50:32,820 they then start listening out for other fish. 651 00:50:32,820 --> 00:50:35,020 By carrying out these experiments, 652 00:50:35,020 --> 00:50:39,700 Steve can create a library of recorded sounds which could help 653 00:50:39,700 --> 00:50:41,140 to recolonize reefs. 654 00:50:43,660 --> 00:50:50,060 A bleached reef is a ghostly, silent place with very few fish around. 655 00:50:50,060 --> 00:50:53,820 But by playing the right sounds, fish could soon come back to a 656 00:50:53,820 --> 00:50:55,580 damaged reef, 657 00:50:55,580 --> 00:50:59,220 and an abundance of fish can lead to the growth of new coral. 658 00:51:02,700 --> 00:51:06,180 When you set up a restoration project, you often quickly get 659 00:51:06,180 --> 00:51:09,620 overgrown by algae, which means that the reef quite quickly dies. 660 00:51:09,620 --> 00:51:14,460 But the fish are really important as herbivores for keeping that away. 661 00:51:14,460 --> 00:51:16,220 We've got to keep these reefs alive. 662 00:51:16,220 --> 00:51:19,140 We've actually got to be throwing them lifelines to give them every 663 00:51:19,140 --> 00:51:21,780 opportunity as one of the greatest wonders on the Earth. 664 00:51:23,820 --> 00:51:27,980 Each new discovery about coral reefs is crucial. 665 00:51:27,980 --> 00:51:29,820 So much life depends on them. 666 00:51:36,540 --> 00:51:40,700 On Heron Island, summer is drawing to a close. 667 00:51:40,700 --> 00:51:43,940 It's now March and the island's fluffy chicks have ventured 668 00:51:43,940 --> 00:51:47,060 from their nests, exploring the world around them. 669 00:51:54,460 --> 00:51:55,740 Up in the trees, 670 00:51:55,740 --> 00:51:59,740 this year's noddy tern chicks have lost most of their down to make 671 00:51:59,740 --> 00:52:01,980 room for their flight feathers. 672 00:52:09,940 --> 00:52:13,580 Flapping like this may not get them very far yet... 673 00:52:15,820 --> 00:52:18,060 ..but this is essential practice 674 00:52:18,060 --> 00:52:20,260 to strengthen growing flight muscles. 675 00:52:26,740 --> 00:52:29,300 And it won't be long until they take to the skies. 676 00:52:34,500 --> 00:52:38,300 On the ground, shearwater chicks are getting their first glimpse 677 00:52:38,300 --> 00:52:39,980 of sunlight. 678 00:52:39,980 --> 00:52:43,460 Many of their parents have now started their long journeys 679 00:52:43,460 --> 00:52:47,100 back to their wintering grounds, leaving the young chicks to teach 680 00:52:47,100 --> 00:52:52,180 themselves how to fly and find their own way across the equator. 681 00:52:52,180 --> 00:52:54,380 We're predicting that we've got a few more weeks 682 00:52:54,380 --> 00:52:55,740 for the shearwaters to leave. 683 00:52:55,740 --> 00:52:57,260 It will be a little bit sad. 684 00:52:57,260 --> 00:53:00,100 You get so used to them being around and the constant noise throughout 685 00:53:00,100 --> 00:53:02,300 the night-time. And the adults will slowly go now. 686 00:53:02,300 --> 00:53:04,940 And then when the chicks go, they go in one big wave. 687 00:53:04,940 --> 00:53:07,780 So you'll just wake up one night and there'll just be no sound. 688 00:53:07,780 --> 00:53:10,020 So it's kind of eerie getting used to that sound 689 00:53:10,020 --> 00:53:11,660 and then just having nothing. 690 00:53:14,100 --> 00:53:17,420 Over the next few weeks, most of the island's birds will embark 691 00:53:17,420 --> 00:53:20,020 on huge migrations across the globe. 692 00:53:23,260 --> 00:53:26,820 But it's not just the bird life that's departing the island. 693 00:53:26,820 --> 00:53:29,940 As the dawn light starts to warm the sand, 694 00:53:29,940 --> 00:53:31,140 new life stirs. 695 00:53:33,740 --> 00:53:37,660 It's time for Heron's turtle hatchlings to embark on the greatest 696 00:53:37,660 --> 00:53:39,420 journey of their lives. 697 00:53:47,980 --> 00:53:50,820 These hatchlings are emerging from the sand 698 00:53:50,820 --> 00:53:52,900 after two months in the dark. 699 00:53:56,300 --> 00:54:00,220 Having never seen water or their mother, instinct drives them 700 00:54:00,220 --> 00:54:01,620 towards the sea. 701 00:54:09,060 --> 00:54:11,380 But danger is all around. 702 00:54:16,500 --> 00:54:19,540 This youngster will need luck on its side to make 703 00:54:19,540 --> 00:54:23,220 it past the swathes of gulls picking off its siblings. 704 00:54:24,380 --> 00:54:26,820 It's a race against all the odds. 705 00:55:32,460 --> 00:55:38,300 This year, 43,000 turtle hatchlings have left Heron Island's beaches 706 00:55:38,300 --> 00:55:41,380 to head off into the open ocean. 707 00:55:41,380 --> 00:55:48,700 And unbelievably, only about 43 of these will make it to adulthood. 708 00:55:48,700 --> 00:55:51,740 The odds are stacked against them, but we need to give them 709 00:55:51,740 --> 00:55:54,380 the best chance possible. 710 00:55:54,380 --> 00:56:00,140 We are releasing seven green sea turtle hatchlings into the sea. 711 00:56:00,140 --> 00:56:04,700 Thanks to Janine's hard work, seven individuals are getting a new chance 712 00:56:04,700 --> 00:56:08,700 at life out into this very precious reef because of the work that's 713 00:56:08,700 --> 00:56:09,980 taking place here. 714 00:56:12,860 --> 00:56:16,540 The contribution of scientists here is vital. 715 00:56:16,540 --> 00:56:19,980 The Great Barrier Reef needs these turtles, as well 716 00:56:19,980 --> 00:56:25,220 as its breeding birds and all other reef residents to thrive. 717 00:56:25,220 --> 00:56:27,700 All species here are connected. 718 00:56:27,700 --> 00:56:32,460 And when these relationships are strained, life falters. 719 00:56:32,460 --> 00:56:37,180 The Great Barrier Reef is essential to life on Earth, but it's facing 720 00:56:37,180 --> 00:56:39,700 some of its toughest challenges yet. 721 00:56:39,700 --> 00:56:43,540 And we risk losing coral reefs before we've even discovered 722 00:56:43,540 --> 00:56:45,540 just how important they are. 723 00:56:53,500 --> 00:56:57,580 This spectacular light show of glowing colours and striking 724 00:56:57,580 --> 00:57:00,660 patterns is only visible to the naked eye 725 00:57:00,660 --> 00:57:02,220 once the sun has set. 726 00:57:03,340 --> 00:57:07,300 The fluorescence is produced by proteins within the corals 727 00:57:07,300 --> 00:57:10,700 that are able to alter the wavelength of light. 728 00:57:14,860 --> 00:57:19,060 Little is known about exactly how they do this, but it's thought 729 00:57:19,060 --> 00:57:22,180 that the process provides the corals with protection 730 00:57:22,180 --> 00:57:26,140 from the harsh rays of the sun, whilst allowing enough light 731 00:57:26,140 --> 00:57:29,220 to reach the algae within their cells that provide 732 00:57:29,220 --> 00:57:30,380 them with food. 733 00:57:31,500 --> 00:57:35,540 It's one of the ingenious mechanisms of coral reefs that have enabled 734 00:57:35,540 --> 00:57:40,020 them to survive for hundreds of millions of years. 735 00:57:40,020 --> 00:57:45,300 Scientists are working tirelessly, searching for novel and innovative 736 00:57:45,300 --> 00:57:48,900 ways to preserve the future of this natural wonder. 737 00:57:49,940 --> 00:57:54,500 It's now down to us to give reefs and our planet that relies 738 00:57:54,500 --> 00:57:56,260 on them a helping hand. 739 00:57:58,460 --> 00:58:01,940 There is no denying that this awe-inspiring kingdom 740 00:58:01,940 --> 00:58:03,700 really is worth saving. 741 00:58:05,220 --> 00:58:09,420 When I think about the idea that we could easily have a world 742 00:58:09,420 --> 00:58:12,940 without a coral-dominated Great Barrier Reef. 743 00:58:12,940 --> 00:58:17,980 I mean, to me, the fact that we can talk about that spurs me on to keep 744 00:58:17,980 --> 00:58:21,660 wanting to say, "No, we still have time and we could still turn 745 00:58:21,660 --> 00:58:24,700 "this thing around and still have these beautiful and diverse 746 00:58:24,700 --> 00:58:27,300 "ecosystems to wonder and be in awe of."