THE DEEP OCEAN

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 THE DEEP OCEAN

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• What is deep ocean: The deep ocean is generally defined as the depth at which light begins to dwindle, typically around 200 meters (656 feet). The top 200 meters of the ocean are known as the sunlight, or euphotic, zone.
• From light to darkness: As said, top 200 meters of the ocean is the euphotic, zone where plants, that convert the sun’s energy into food via photosynthesis, form the basis of the food chain at these depths, with sunlight. At 200 meters depth, we enter the twilight zone, where light starts to decrease rapidly. Ocean depths greater than 1,000 meters (3,280 feet) are completely devoid of light and photosynthesis does not take place.
• Why sunlight is crucial: Sunlight doesn't just provide the energy for photosynthesis: it also heats the water. This means that the deep ocean is also cold – with an average temperature of only 4°C (39°F). These depths are also subject to extreme pressure, from about 40 to over 110 times the pressure of Earth’s atmosphere.
• Life finds a way: This means the “deep” is the part of our ocean that is dark, cold, food-poor, subject to intense pressure, and typically deeper than 200 meters. Despite these extreme conditions, life has found a way to thrive even at great ocean depths, and with each new mission to explore the deep, new discoveries are made that increase our understanding of one of the largest, but least understood, living places on our planet. By 200 meters depth, there is no longer enough sunlight available to phytoplankton, or any plant-like organism, for photosynthesis (the process these organisms use to convert the sun’s energy into food – organic molecules). Water, and the particles suspended in the water, absorb and reflect light.
• Cold, dark, damp: The ocean surface near the equator is the hottest because it receives the most continuous direct sunlight. The deeper into the ocean you descend, the less sunlight there is. This results in less warming of the water. As said earlier, the deep ocean is cold – with an average temperature of only 4°C. Cold water is also more dense, and as a result heavier, than warm water. Older water sinks below the warm water at the surface, which contributes to the coldness of the deep ocean.
• Estimating the age: This means the deep sea is the part of our ocean that is dark, cold, food-poor, and typically deeper than 200 meters. Coincidentally, that depth is also a good approximation of the average depth of the edge of the continental shelf (the portion of a large continental landmass that dips below water – the submerged coastlines). Go beyond the continental shelf and the steepness of the slope increases dramatically, plunging more rapidly into the cold, dark, deep sea.

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