Ocean is the largest living system on Earth and has a profound impact on our planet’s weather, temperature and food supply. Its depths and waters contain billions of species ranging from microscopic algae to large cetaceans. It provides crucial environmental services like climate regulation and a means of transportation. The ocean is also rich in natural resources such as timber and fiber from mangroves and seagrass beds and a potential source of renewable energy from wave and tidal power.
Oceans are complex systems that form, move and change over time. Their boundaries and structure are continually changing because of processes such as plate tectonics, post-glacial rebound and sea level rise. The physical characteristics of the ocean, such as temperature, salinity and density, are constantly changing, too. Ocean currents are driven by wind and the Coriolis effect, a force that causes them to rotate clockwise in the Southern Hemisphere and counterclockwise in the Northern. The surface ocean is divided into zones based on their physical properties. The photic zone, the zone where light penetrates to a depth of about 200 meters in open water, lies between the surface and the thermocline (temperature gradient). The next zone is the mesopelagic, lying between the thermocline and the bathypelagic, which is typically around 1,000 m (3,300 ft). The bottom-dwelling hadalpelagic zone is at 6,000 m (21,000 ft) or more.
Biological oceanography is the study of living organisms in the ocean. It combines the disciplines of biology and geology to investigate how living things interact with the physical environment. It encompasses a wide variety of topics, from the chemistry and physics of marine matter to the ecology and evolution of marine life.
The ocean is the habitat of nearly two million species of plants and animals, including humans. These creatures range in size from the microscopic phytoplankton that make up about 70% of the world’s biomass to the enormous blue whale, which can be 33 m (108 ft) long. Phytoplankton, bacteria and other protists, algae, fish, invertebrates and marine mammals are all found in the ocean.
The ocean has a high concentration of dissolved gases, such as oxygen, carbon dioxide and nitrogen. When fossil fuels are burned, they release carbon dioxide into the atmosphere, increasing its levels in the ocean. This, in turn, can reduce the amount of oxygen in the water and lead to ocean acidification.
The ocean is the most important habitat on the planet for many species of plants and animals, and it provides essential services to humankind. It regulates the climate, supports fisheries and other forms of marine recreation, serves as a highway for global shipping and provides raw materials that are vital to the manufacture of our daily lives, such as fibres, chemicals and pharmaceutical drugs. It also absorbs carbon dioxide and other harmful gases from the air, protecting our planet’s atmosphere. In addition, the ocean supplies us with freshwater and a source of food. The ocean is an important part of our daily lives, but we must take care not to abuse it.