The boundary between land and sea is an exciting place, with animals constantly coming and going. From the open oceans, millions of seabirds are forced to come onto land to breed. Sea eagles steal kittiwake chicks from their nesting ledges. Turtles lay their eggs in the sand and marine mammals haul themselves out to fight on the beaches. Sea lions emerge from the kelp to give birth, while killer whales come crashing into n the surf to snatch the sea lions' young.
Tides govern marine life. Tidal marshes are some of the most productive parts of the world. Numerous plants support numerous animals, yet life is not easy; predators are attracted to these enormous quantities of food, forcing animals to seek constant protection from attack. Relief comes with the crashing waves, as the tides flow once more. Between the tides, when the sands become depleted of food and air, the worms, clams and shrimps just endure the expected pause.
Shafts of sunlight radiate through a green sea. This blazing light is the vital source of energy used by the countless billions of plankton which grow every spring and summer in the world's temperate sea, the richest of all habitats. Forests of giant kelp, the fastest growing plant in the world, harbour thousands of animals. Sharks move in to pick off the vulnerable. Sea otters, brilliantly coloured anemones, squid and exquisite leafy dragons are just a few of the other creatures that live in this cool, rich water.
Bathed in warm, clear tropical water and brilliant sunlight, coral reefs are the rainforests of the sea. Surrounded by ocean deserts, they are rich oases of life. Spectacular numbers make it necessary to stand out to survive. This competition is highly visible as brightly coloured fish compete for food, territory and mates. But the corals themselves are also dynamic. Incredible time-lapse photography shows the dramatic formation of a coral reef, portraying its myriad inhabitants and its ultimate destruction.
Endless blue stretches in every direction. The sea bed is a staggering 8km deeper down and the nearest island is 500km away. There is nothing save the burning sun above and the blackened abyss below. How, then, does life exist?
Life on the edge of a frozen sea is tough. Pack-ice at both poles is constantly on the move and, in winter, freezes solid with air temperatures 70 degrees below freezing. Only in spring, with the retreating ice and light reaching the water, does life begin again. Plankton blooms and feeds vast hordes of migrating fish, birds, whales, seals and polar bears. Walruses rake the seabed for clams. Minke and humpback whales gorge themselves on gigantic swarms of krill. But it is a brief indulgence, for the ice soon returns and pushes life back into the ocean.
The blue whale is a perfect symbol for the oceans, the vast blue expanse that dominates our planet while remaining largely unexplored and mysterious. Yet the oceans are an integral part of our lives. Their influence dominates the world's weather systems. They support an enormous range of life, from the largest whales to the smallest plankton, from hordes of sea birds to lonely deep-sea fish. All this is governed by a complex system of biological and physical forces. This first episode demonstrates the sheer scale, power and complexity of our Blue Planet.
The deep sea - which gets darker till no more sunlight penetrates at about a kilometre depth and ever colder closer to the bottom of the ocean - covers most of the planet and is, thus, by far the largest habitat on earth, yet, it has been explored less than space.
See behind the scenes of this series, concentrating on how the filmmakers worked together with scientific advisers from practically every field of marine science.
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