Correct option is C
To determine the correct increasing order of fluxes in the phosphorus cycle, we analyze the movement of phosphorus through different pathways:
- Natural Chemical Weathering (D) – Smallest Flux
- Phosphorus originates from rocks and is released very slowly through weathering and erosion.
- This is the smallest flux in the phosphorus cycle as it occurs over geological timescales.
- Terrestrial Runoff into Oceans (C) – Moderate Flux
- Phosphorus moves from soil into water bodies via erosion and leaching from land to rivers and eventually to oceans.
- This flux is larger than weathering but smaller than internal cycling because it depends on rainfall, soil type, and human activities like deforestation and agriculture.
- Internal Cycling in Terrestrial Ecosystems (A) – High Flux
- Within terrestrial ecosystems, phosphorus is continuously recycled through plant uptake, decomposition, and soil microbial activity.
- This flux is higher than runoff (C) because phosphorus is retained and utilized efficiently within ecosystems before any loss occurs through leaching.
- Internal Cycling in Marine Ecosystems (B) – Largest Flux
- Oceans store the most phosphorus and cycle it through plankton, fish, marine sediments, and deep-sea currents.
- Phosphorus recycling in the ocean is vast, involving a larger volume compared to land-based cycles.
Thus, the correct increasing order of magnitude is: D < C < A < B, making Option (C) correct.
