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Surface waters

A variety of animals swimming in the sunlit surface waters of the ocean The richest variety of life in the oceans is found in the top 200 metres (about 660 feet): the “roof” of the ocean. Here, light from the sun penetrates the water, allowing tiny plants, called phytoplankton, to grow. This is food for tiny animals called zooplankton, which forms a vital part of the ocean food web, to which all ocean creatures are linked. Small fish, for example, feed on the zooplankton and are themselves preyed upon by larger predatory fish, such as tuna or sharks. They also fall prey to sea turtles, and mammals such as seals, dolphins and whales


Humpback whales bubble-net fishing off the coast of Alaska. The whales swim in a circle blowing bubbles below a shoal of fish....Read More >>Humpback whales bubble-net fishing off the coast of Alaska. The whales swim in a circle blowing bubbles below a shoal of fish. The ring of bubbles traps the shoal and becomes smaller and smaller as the whales move in to feed.
Diatoms, a type of algae, one of the commonest phytoplankton, seen under a microscope

Plankton

Unlike land plants, oceanic plants cannot put down roots into the ground. Instead, ocean plants, called phytoplankton, are microscopic in size and float around in the ocean currents, living off the chemical nutrients dissolved in the water. 

The top 200 m (660 ft) of the ocean is known as the photic zone, after the Greek word phos, meaning "light". About 90% of all marine life lives in the photic zone.

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