The Ocean – Home to More Than 700,000 Species of Marine Life

Ocean is the world’s largest body of water, covering more than 70% of Earth’s surface. It is vital for life on our planet because it creates oxygen, carries food and energy to living things, protects coastlines and provides a natural habitat for marine plants, fish and other animals. The ocean also provides important routes for travel and trade, and is a major source of raw materials used in building and making products.

Scientists have found that there are over 3,500 species of sea plants and over 700,000 types of animals in the ocean. These include microscopic plankton and small floating organisms, such as zooplankton (tiny drifting animals with shells of calcium carbonate), which form the base of most marine food webs. Many larger animals feed on these tiny organisms, or eat the dead zooplankton that drift down to the ocean floor and eventually decompose to become part of the sediment. The ocean is also critical for the carbon cycle, which involves moving carbon (as a gas or in a solid) between air, land and sea.

The ocean is formed by tectonic plates that float on a layer of hot, semi-liquid rock called the mantle. The plates move slowly together and apart, sometimes separating so that hot molten rock rises from deep within the Earth to fill the gap, creating new ocean floors and underwater mountain ranges over millions of years. This process is known as seafloor spreading.

Water from the ocean flows to the land and back again, in a cycle called the water cycle. This cycle carries dissolved minerals and salts from rocks and soil to the ocean, where they become part of the salty water that covers more than 70 percent of our planet’s surface.

In addition, ocean currents are partly controlled by the fact that the Earth rotates, a phenomenon known as the Coriolis effect. This causes large systems, such as winds and ocean currents that would otherwise move in straight lines, to veer to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

Oceans are complex, dynamic places with a huge variety of creatures and landscapes. They are home to an immense array of ecosystems and are essential for sustaining life on our planet.

The ocean plays an important role in providing a wide range of “ecosystem services” that humans need, including clean air, regulating temperature, stabilizing climate, providing food and energy, and absorbing carbon. When an ecosystem is damaged, however, it can take a long time for it to recover and return its original function.

It is important to understand and appreciate the value of the ocean, as well as to work together to protect it. Ocean-based industries provide jobs for fishermen, lifeguards, surf instructors, harbours, marine-based tour operators, water sports businesses and holiday accommodations. Research has shown that ocean views and visits can even have a therapeutic effect, lowering stress levels and heart and breathing rates.

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