Aphotic zone
Definition
The aphotic zone is the part of an ocean or lake where no sunlight penetrates, making photosynthesis impossible. It typically begins at depths around 200 meters and extends to the ocean floor.
5 Must Know Facts For Your Next Test
- The aphotic zone is also known as the midnight zone due to its complete darkness.
- Organisms in the aphotic zone often rely on chemosynthesis for energy.
- Temperatures in the aphotic zone are near freezing, averaging around 2-3 degrees Celsius.
- Pressure increases significantly with depth in the aphotic zone, reaching up to 1000 times atmospheric pressure at sea level.
- Bioluminescence is common among species living in the aphotic zone.
Review Questions
- At what approximate depth does the aphotic zone begin?
- Why can't photosynthesis occur in the aphotic zone?
- What adaptation do many organisms in the aphotic zone have for finding food and avoiding predators?
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Related terms
photic_zone: The upper layer of a body of water that receives sufficient sunlight for photosynthesis.
thermocline: A steep temperature gradient in a body of water marked by a layer above and below which the temperature is different.
chemosynthesis: The process by which certain organisms use chemical energy to produce carbohydrates, often occurring in environments without sunlight.
