Aphotic zone
Definition
The aphotic zone is the portion of a body of water where sunlight does not penetrate, making photosynthesis impossible. It typically lies below 200 meters in the ocean, beyond the reach of light.
5 Must Know Facts For Your Next Test
- The aphotic zone is also known as the midnight zone due to its complete darkness.
- This zone constitutes the largest part of marine environments by volume.
- Organisms in the aphotic zone rely on chemosynthesis or consumption of organic matter for energy.
- Temperatures in this zone are consistently cold, usually around 4°C (39°F).
- Pressure increases significantly with depth in the aphotic zone, affecting organism adaptation.
Review Questions
- Why is photosynthesis not possible in the aphotic zone?
- What adaptations do organisms have to survive in the aphotic zone?
- How does pressure and temperature change as you go deeper into the aphotic zone?
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Related terms
photic_zone: The upper layer of a body of water that receives enough sunlight for photosynthesis.
thermocline: A distinct layer in a body of water where temperature changes more rapidly with depth than it does in the layers above or below.
chemosynthesis: The process by which some organisms use chemical energy to produce carbohydrates, typically occurring in environments without sunlight.
