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How far does light travel in the ocean?

Light may be detected as far as 1,000 meters down in the ocean, but there is rarely any significant light beyond 200 meters.

illustration of how far light travels in the ocean.

The ocean is divided into three zones based on depth and light level. Although some sea creatures depend on light to live, others can do without it. ‘Photic’ is a derivative of ‘photon,’ the word for a particle of light. A full transcript is available that presents this infographic content in plain text.

Sunlight entering the water may travel about 1,000 meters into the ocean under the right conditions, but there is rarely any significant light beyond 200 meters.

The ocean is divided into three zones based on depth and light level. The upper 200 meters of the ocean is called the euphotic, or "sunlight," zone. This zone contains the vast majority of commercial fisheries and is home to many protected marine mammals and sea turtles.

Only a small amount of light penetrates beyond this depth.

The zone between 200 meters and 1,000 meters is usually referred to as the “twilight” zone, but is officially the dysphotic zone. In this zone, the intensity of light rapidly dissipates as depth increases. Such a minuscule amount of light penetrates beyond a depth of 200 meters that photosynthesis is no longer possible.

The aphotic zone exists in depths below 1,000 meters. Sunlight does not penetrate to these depths and the zone is bathed in darkness. The aphotic zone is further subdivided into the bathypelagic zone (or midnight zone) between 1,000 and 4,000 meters, the abyssopelagic (or the abyss) between 4,000 and 6,000 meters, and the hadopelagic zone (or hadal zone) 6,000 meters and deeper.


Infographic Transcript: Distance Sunlight Travels in the Ocean

  • The left side of this graphic shows a measuring stick against a representation of the ocean; it shows three depths: sea level, 200 meters, and 1,000 meters and deeper.
  • The middle portion of the graphic shows the ocean divided into three zones. The first division from sea level to 200 meters is labeled as the euphotic (sunlight) zone and says "sunlight rarely penetrates beyond this zone." Graphic representations of tuna are shown swimming in this first zone. The second division from 200 meters to 1,000 meters is labeled as the dysphotic (twilight) zone and says "sunlight decreases rapidly with depth; photosynthesis is not possible here." Graphic representations of shrimp, swordfish, and hatchet fish are shown swimming in this second zone. The third division is labeled from 1,000 meters and deeper and is labeled as the aphotic zone and says "sunlight does not penetrate; the zone is bathed in darkness." Graphic representations of angler fish and giant squid are shown swimming in this zone.
  • The division labeled 'aphotic zone' contains this additional text: "The aphotic zone incudes: The bathypelagic (midnight) zone between 1,000-4,000 meters; the abyssopelagic (abyss) zone between 4,000-6,000 meters; and the hadopelagic (hadal) zone is 6,000 meters and deeper.
  • A solid blue thin line is at the bottom of the graphic shows the website address of the National Ocean Service and the NOAA logo.
Last updated:
11/05/21

Author: NOAA

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