alleryStart learning →How long does the average phosphate ion stay in the ocean?
ABetween 200 and 1,000 years
BBetween 20,000 and 100,000 years
CBetween 2,000 and 10,000 years
DBetween 2 and 10 million years
Answer & Solution
Correct answer: B. Between 20,000 and 100,000 years
1. Phosphorus has no significant gas phase, so it cannot move quickly through the atmosphere.
2. It reaches the ocean by runoff, groundwater flow and river flow.
3. Getting back to land depends on sediment forming and then being uplifted geologically.
4. That return route works on geological rather than biological timescales.
5. So the average phosphate ion sits in the ocean between 20,000 and 100,000 years.
6. This slowness is one reason phosphorus is so often the limiting nutrient in aquatic systems.
7. Ranges of hundreds or a few thousand years would imply a fast atmospheric route that does not exist.
8. A range of millions of years overstates it, since the figure quoted tops out near 100,000.
_Source: OpenStax Biology 1e (CC BY 4.0), Chs 44 and 46, section 46.3 Biogeochemical Cycles_
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