Nutrient Supply to Planetary Biospheres From Anoxic Weathering of Mafic Oceanic Crust

Phosphorus is an essential element for life, and the phosphorous cycle is widely believed to be a key factor limiting the extent of Earth's biosphere and its impact on remotely detectable features of Earth's atmospheric chemistry. Continental weathering is conventionally considered to be the only source of bioavailable phosphorus to the marine biosphere, with submarine hydrothermal processes acting as a phosphorus sink. Here, we use a novel Si-29 tracer technique to demonstrate that alteration of submarine basalt under anoxic conditions leads to significant soluble phosphorus release, with an estimated ratio between phosphorus release and CO2 consumption ( n-ary sumation PO43-/ n-ary sumation CO2) of 3.99 +/- 1.03 mu mol mmol(-1). This ratio is comparable to that of modern rivers, suggesting that submarine weathering under anoxic conditions is potentially a significant source of bioavailable phosphorus to planetary oceans and that volatile-rich Earth-like planets lacking exposed continents could develop robust biospheres capable of sustaining remotely detectable atmospheric biosignatures.

Automated summary

The study demonstrates that submarine weathering under anoxic conditions is a significant source of bioavailable phosphorus, with a release ratio comparable to modern rivers. This suggests that Earth-like planets lacking exposed continents may have robust biospheres capable of sustaining detectable atmospheric biosignatures.