Which ocean depth zone extends from the sea surface down to approximately 200 meters, representing the only oceanic layer that receives sufficient sunlight for photosynthetic phytoplankton to generate primary production?

Answer and explanation

Correct answer: B. Epipelagic zone (Photic / Sunlight zone)

  1. Step 1: Sunlight penetrates seawater with diminishing intensity as depth increases, dictating marine ecological zonation.
  2. Step 2: The epipelagic zone (0 to 200 m) contains more than 90% of all marine life because adequate solar irradiance allows phytoplankton, seaweeds, and seagrasses to conduct photosynthesis and sustain ocean food webs.
Answer
Epipelagic zone (Photic / Sunlight zone)
Why not the others: 'Mesopelagic zone (Twilight zone)' The mesopelagic zone (200 m to 1,000 m) receives faint light insufficient for photosynthesis, home to bioluminescent creatures; 'Bathypelagic zone (Midnight zone)' The bathypelagic zone (1,000 m to 4,000 m) is perpetually dark, cold, and subject to intense hydrostatic pressure; 'Abyssopelagic zone (Abyss)' The abyssopelagic zone (4,000 m to 6,000 m) encompasses the deep ocean floor, where temperatures hover near freezing.

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