Ocean is a huge body of salt water that covers about 71 percent of Earth’s surface. It is home to many animals and plants, including mammals, fish, mollusks, algae, and more. It is also a source of energy, oxygen, and food for all living things. It influences the Earth’s climate by transferring heat from the Equator to the poles and evaporating to bring rain over land. It is also a global system of currents that transport nutrients and other materials.
The chemistry and physical properties of the ocean are controlled by many natural processes, such as the sun’s heat and the movement of wind and gravity. Human activities affect the ocean in a variety of ways, too. These include pollution, changing ocean chemistry (such as acidification), and changing the habitat of the ocean. These changes can impact biological diversity and the survival of organisms.
In addition to the countless species of sea life, oceans provide many economic benefits for people. Fishing and tourism are two of the largest ocean-based industries, employing millions worldwide. Other ocean-based industries include generating renewable energy, mining minerals, and capturing carbon dioxide. These activities require extensive marine infrastructure and technology. In the future, they could be enhanced by new technologies for exploring deeper parts of the ocean, extracting medicines components, and cultivating algae and seaweed for food and fuel.
Scientists are still discovering the vast, hidden world of the ocean. In fact, it is estimated that more than 91% of the ocean’s biodiversity remains unknown to science. This is partly because of the ocean’s immense size: it has an area of 3.6 billion square miles. Its deepest point is the Mariana Trench, at a depth of over 11,000 meters (36,000 feet).
The ocean has a vital role in the Earth’s water cycle. Warm currents in the ocean heat the air, which rises and forms clouds. Then, as the clouds move over the land, they release water, which creates rain. This water flows over, through, and into every plant, animal, and human on the planet before returning to the Ocean. Without this important water cycle, our planet would be a desert.
Streams of water called ocean currents form and move across the ocean’s surface, influenced by the ocean’s temperature, salinity, geological features, the shape of the coast, and the Earth’s rotation. Ocean currents bring fresh water from rivers to the sea, carry salts and other materials from the tropics to the poles, and transport oxygen to organisms in the entire ocean.
The ocean is the most diverse ecosystem on Earth. Its living organisms range from microscopic bacteria to the largest animal on the planet, the blue whale. The most abundant living organisms in the ocean are the tiny photosynthetic algae and bacteria called phytoplankton, which make up more than half of the total mass of the ocean. These tiny organisms form the basis of the ocean food chain. Phytoplankton also absorbs carbon dioxide and releases oxygen.