Скачать или смотреть Deep sea/ആഴക്കടൽ സവിശേഷതകൾ

The deep sea is broadly defined as the ocean depth where light begins to fade, at an approximate depth of 200 m. Conditions within the deep sea are a combination of low temperatures, darkness, and high pressure. The deep sea is considered the least explored Earth biome as the extreme conditions make the environment difficult to access and explore.
Natural light does not penetrate the deep ocean. Hence life in this area of the ocean must depend on energy sources from elsewhere. Except for the areas close to the hydrothermal vents, this energy comes from organic material drifting down from the photic zone. pressure in the ocean increases by about 1 atmosphere for every 10 meters of depth. Salinity is remarkably constant throughout the deep sea, at about 35 parts per thousand. However in landlocked ocean like the Mediterranean and Red Sea salinity is very different. The two areas of greatest temperature gradient in the oceans are the transition zone between the surface waters and the deep waters, the thermocline, and the transition between the deep-sea floor and the hot water flows at the hydrothermal vents. Below the thermocline, the water mass of the deep ocean is cold and far more homogeneous.
Oceanographers divide the majority of the ocean midwater into five broad zones. From ocean surface to 200m depth, the area is called epipelagic zone and this zone receives sunlight. The area of the ocean between 200-1,000 m depth is called the mesopelagic. This zone also called the twilight zone, this area receives only faint, filtered sunlight, allowing no photosynthetic organisms to survive. Many animals have adapted to the near-darkness with large eyes and counterillumination. The bathypelagic zone is between 1,000 and 4,000 m depth. It is an area void of light (called aphotic) and at 4 degrees celsius temperature. Animals here create their own bioluminescent light . The Abyssopelagic extends from 4,000-6,000 m down to the seafloor or abyssal plain. The hadalpelagic is the very deepest part of the ocean that includes the ocean trenches. It extends from 6,000 meters to the very bottom of the Mariana Trench at 10,994 meters.
Organisms living within the deep sea have a variety of adaptations to survive in these conditions. Organisms can survive in the deep sea through a number of feeding methods including scavenging, predation and filtration, with a number of organisms surviving by feeding on marine snow. Marine snow is organic material that has fallen from upper waters into the deep sea.