But urchins can swarm in vast numbers and even attack and fell the kelp forest itself, creating vast 'urchin barrens'. When spiny urchins invade and graze their crops, the Garibaldi desperately pick them off.

In clearings, bright orange male Garibaldi fish guard territories of short turf seaweed. To outwit her nemesis, the pyjama shark, she uses ingenious tactics, never filmed before.Īlong the Pacific coast of North America stand, at 60 metres high, the largest and perhaps most diverse kelp forests in the world. Almost a hundred different species of shark patrol these waters, driving one resident - the common octopus - to become the ultimate escape artist. The most bountiful kelp forests are found off the tip of southern Africa, where two great oceans collide. They are the most abundant but fiercely competitive places in the ocean to live. Here sunlight powers the growth of enchanted forests of kelp, mangroves and prairies of sea grass. In top predators like pilot whales, the toxic chemicals can build up to lethal levels.It's our green seas, not the blue, that bring life to our oceans. As plastic breaks down it combines with other pollutants that are consumed by vast numbers of marine creatures. One possible cause of death is poisoning by its own mother's contaminated milk. In the Atlantic waters off Europe we follow a family of pilot whales whose calf has recently died. Globe-spanning currents carry it into the heart of every ocean, often with tragic consequences. An estimated eight million tons of plastic is dumped into the oceans every year. Yet even in the big blue, thousands of kilometres from land, there is evidence of human activity. And in the freezing south Atlantic, a pair of ageing wandering albatrosses give their all to raise their very last chick. Scientists now think it might be here that the pregnant females give birth to their pups in the safety of the depths.

The pregnant females make an epic journey across the Pacific to the Galapagos Islands. We get closer to solving the mystery of where the biggest fish in the sea, the whale shark, gives birth. The episode follows two very different ocean voyagers that show amazing care. Raising your young in this great wilderness is a huge challenge. New aerial footage reveals, for the first time, the truth to a centuries-old sailors' legend of the 'boiling seas' - the spectacular feeding frenzy of 90kg tuna and dolphins smashing through the lantern fish shoals turning the sea white with foam. We witness super pods of up to 5,000 spinner dolphins racing to herd vast shoals of lanternfish, briefly caught at the surface where it is thought they spawn. Sometimes there is a brief explosion of food in this marine desert, but ocean hunters must be fast to make the best of this bonanza. The jelly-like Portuguese man-of-war can harness sail power to fish with its deadly tentacles. Jellyfish cross entire oceans feeding on whatever happens to tangle with their tentacles. Over half of all animals in the open ocean drift in currents. Here they remain until adulthood, adrift on the high seas in relative safety away from coastal predators. They leave the crowded waters of the coast and head to the open ocean, where they use floating debris like logs as life rafts. Only recently have we begun to solve the mystery of where baby turtles disappear to in their early years.

Many smaller creatures find sanctuary in this great wilderness. With special pressure-proof cameras, we witness record-breaking feats of endurance as they hunt for squid a kilometre down into the abyss. They live for 80 years, and we are only now beginning to learn the extraordinary complexity of their language of clicks - thought to coordinate the whole family in everything from childcare to hunting. Sperm whales have the largest brains in the world. We witness feats of incredible endurance, moments of high drama and extraordinary acts of heart-wrenching self-sacrifice.Įvery animal in the big blue must find their own unique way to survive. This episode reveals what it takes to survive in this savage and forbidding world. Yet it's home to some of the biggest and most spectacular creatures on earth. It's a vast marine desert where there is little to eat and nowhere to hide. The big blue is the world's greatest wilderness, far from shore and many kilometres deep.

The blue planet seas of life bbc