The oceans cover three-quarters of our planet, and their influence dominates the world's weather systems. The first program in the series aims to introduce the viewer to the sheer scale and power of the Blue Planet. We will review the forces, both physical and biological, that make the oceans work and explain exactly where and why life congregates. All life in the oceans depends on a constant supply of nutrients and, more than any other factor, the ocean's currents control their distribution. But nutrients alone are not enough to produce life. The sun’s annual journey north and south across the planet injects energy into the oceans on a seasonal basis. In Alaska the spring return of the sun to the Northern Hemisphere signals the return of millions of herring to shallow waters to spawn. Spring in Alaska also signals the return of the Grey whales to the Bearing Sea from their breeding grounds in the Sea of Cortez. The sun's daily cycle is also vital. Each sunset is the starting gun for the largest migration on the planet. Millions of animals from the deeper ocean travel to shallower water to feed off the energy injected during the day into the surface. One of the most spectacular examples of vertical migration is the annual appearance of Opulescent squid off the coast of California. Millions of squid that normally spend their lives at depth come to the shallows in enormous shoals to breed and lay their eggs over a number of days. The moon’s daily cycle also plays a key role in controlling the oceans. Its gravitational pull is responsible for the ebb and flow of the tides, which is closely related to life in the oceans. Each year on the coast of Costa Rica, turtles start appearing from the sea. Over just three nights a hundred thousand turtles come to one beach just a mile long. This spectacular breeding congregation, an arribada, seems to be totally coordinated round the phases of the moon.moreless
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