What is the oceanic zone that extends from the surface down to 200 meters, where light supports photosynthesis?

• A. Euphotic Zone
• B. Disphotic Zone
• C. Aphotic Zone
• D. Splash Zone

Answer: (A)

In ocean ecosystems, the depth range where enough light reaches the water to drive photosynthesis is the sunlit, or euphotic, zone. This layer extends from the surface down to about 100–200 meters, depending on water clarity. In clear open water, light can penetrate to roughly 200 meters, supporting photosynthesis by phytoplankton and other light-driven organisms. The disphotic (twilight) zone receives some light but not enough for significant photosynthesis, while the aphotic (dark) zone has little to no light. The splash zone isn’t a true oceanic vertical zone; it’s a shoreline area above water. So, the description of light supporting photosynthesis from the surface down to about 200 meters best matches the euphotic zone.