The phosphorous sinks are the ocean and ocean sediments.
The ocean holds $3 \times 10^{15}$ moles of phosphorous.
The annual amount of phosphorous input into the ocean, and well as the amount of burial of phosphorous as sediment is on the order of $10^{10}$ moles.
See Phosphorous Accumulation in Marine Sediments and the Oceanic Phosphorous Cycle for a detailed analysis.