Phyllosilicate adsorption limited phosphorus bioavailability in early ferruginous oceans.

Abstract

The phosphorus (P) cycle links the co-evolution of the biosphere and geosphere over geologic time. Modern P availability is primarily controlled by mineral adsorption, but how such processes might have operated under early Earth's anoxic conditions remains unclear. Here, we combine experimental and theoretical investigations of P adsorption onto common phyllosilicates to evaluate their role in the early P cycle. We show that the P adsorption would have been significantly enhanced in early ferruginous waters, primarily through dissolved Fe(II) bridging between orthophosphate and mineral surfaces. Such enhanced P adsorption onto phyllosilicates could have facilitated the riverine transport of bioavailable P during Archean anoxic continental weathering, yet also promoted its rapid burial in shallow marine settings. Moreover, phyllosilicate adsorption would have limited dissolved P release during seafloor weathering in the Archean and Proterozoic oceans. These processes collectively could have limited dissolved P availability for the origin and evolution of early life.