Which zone receives very little sunlight and only blue-green wavelengths?

• A. Surface zone
• B. Deep zone
• C. Middle zone
• D. Epipelagic zone

Answer: (C)

Light becomes scarce quickly as you go down in the ocean, and the only light that remains at certain depths is mainly blue-green. That depth range is the twilight or mesopelagic zone, often referred to as the middle zone in some curricula. In this zone, there isn’t enough light for photosynthesis, and longer wavelengths like red are absorbed higher up, leaving blue-green light to penetrate. So the middle/twilight zone is the best description for a layer with very little sunlight and a light spectrum dominated by blue-green. The surface or epipelagic zone is bright and sunlit, while the deepest layers have almost no light at all.