Which zone receives enough light for photosynthesis?

• A. Photic zone
• B. Aphotic zone
• C. Intertidal zone
• D. Open ocean

Answer: (A)

Light availability is what enables photosynthesis, so the zone that receives enough sunlight to power photosynthetic organisms like phytoplankton is the photic zone. In clear ocean water, sunlight can penetrate the upper roughly 0 to 200 meters, allowing photosynthesis to occur there. Below this depth, light is too weak, and the aphotic zone lacks sufficient illumination for photosynthesis. The intertidal zone is a coastal region influenced by tides and air exposure, not defined by a depth where light enables photosynthesis, and the open ocean describes a broad area that includes both lighted and dark layers. So the photic zone is the layer where enough light for photosynthesis exists.