Drivers of the global phosphorus cycle over geological time

Abstract

Phosphorus is a key limiting nutrient of terrestrial and marine primary production. Thus, the global phosphorus cycle is intimately linked with the carbon cycle and influences climate over geological timescales. In this Review, we explore the environmental forcings governing the global phosphorus cycle over the last ~3.0 billion years, focusing on sources from continental weathering and removal through burial in marine sediments. Modern continental weathering of phosphorus is dominated by apatite dissolution (25.4 ± 5.4 × 1010 mol year−1) and organic matter oxidation (1.2 ± 0.2 × 1010 mol year−1), and is governed by local temperature, biota, tectonic activity and atmospheric partial pressures of oxygen and carbon dioxide. Of this modern weathered phosphorus flux, rivers deliver 2.8 ± 0.2 × 1010 mol year−1 dissolved phosphorus and 20 ± 6 × 1010 mol year−1 reactive particulate phosphorus to the ocean, where phosphorus has a residence time of 11,000–27,000 years. Phosphorus burial in marine sediments is the primary sink term and balances with phosphorus weathering on geological timescales. Burial rates are governed by organic matter flux, ocean chemistry, redox conditions, temperature and biological activity in sediments. Enhanced resolution of empirical observations combined with sophisticated data analysis is needed to robustly constrain how environmental drivers influence the phosphorus cycle and, thus, climate. The phosphorus cycle limits primary production on geological timescales, influencing climate. This Review explores the environmental drivers impacting the rates of continental weathering and phosphorus burial in marine sediments, which are the primary sources and sinks in the global phosphorus cycle.