Phosphorus bioavailability
Phosphorus (P) is an essential nutrient and limits primary productivity in the ocean over geological timescales. Today, P is predominantly delivered to the ocean via continental weathering, and it is cycled many times through the marine biosphere before ultimately being buried in marine sediments. The rate of P supply and recycling allows high primary productivity in surface waters of the modern ocean; however, this balance is likely to have been different in the Archean. Here, we review the processes affecting the input, internal cycling, and output of P in the Archean ocean. We find that P may have been more widely available for the origin of life than previously considered, due to less efficient sinks. Since the origin of life, P has likely had limited productivity. Archean P delivery rates are unlikely to have exceeded those of the modern Earth. Furthermore, slow internal recycling and scavenging of P by iron minerals are likely to have kept the Archean P reservoir small, with efficient removal in sediments. Growth of the marine sulfate reservoir in the late Archean may have enabled P recycling, initiating a positive feedback wherein increasing primary productivity fueled oxygenation of the atmosphere during the Great Oxidation Event.
