A Five-stage Evolution of Earth's Phosphorus Cycle

Phosphorus (P) is a key biological nutrient and probably the ultimate limiter of marine productivity during Earth history. In recent years, a wealth of new knowledge has revolutionized our understanding of the global P cycle, yet its long-term evolution remains incompletely documented. In this paper, we review the effects of three major controlling factors on the long-term evolution of the global P cycle, i.e., tectonics, marine redox conditions, and bio-evolution, on the basis of which a five-stage model is proposed: Stage I (>∼2.4 Ga), tectonic-lithogenic-controlled P cycling; Stage II (∼2.4 Ga to 635 Ma), low-efficiency biotic P cycling; Stage III (∼635 Ma to 380 Ma), transitional biotic P cycling; Stage IV (∼380 Ma to near-modern), high-efficiency biotic P cycling; and Stage V (Anthropocene), human-influenced P cycling. This model implies that the earlier-proposed Ediacaran reorganization of the marine P cycle may represent only the start of a ∼250–Myr–long transition of the Earth's P cycle (Stage III) between the low-efficiency biotic mode of the Proterozoic (Stage II) and the high-efficiency biotic mode of the Phanerozoic (Stage IV). The development of biologically-driven, high-efficiency P cycling may have been a key factor for the increasing frequency and volume of phosphorite deposits since the late Neoproterozoic.