alleryStart learning →Below roughly 200 m in the ocean, what changes for photosynthesis?
AIt stops, since light no longer reaches
BIt speeds up, since water is cooler
CIt stops, since oxygen no longer reaches
DIt speeds up, since pressure is higher
Answer & Solution
Correct answer: A. It stops, since light no longer reaches
1. Water absorbs light, so less and less reaches each successive depth.
2. Past about 200 m no light gets through at all, which defines the aphotic zone.
3. Photosynthesis needs light, so it cannot happen there.
4. Most of the ocean by volume is aphotic and therefore has no photosynthesis.
_Source: OpenStax Biology 1e (CC BY 4.0), Chs 44 and 46, section 44.4 Aquatic Biomes_
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