The oceanic phosphorus cycle

Phosphorus is undeniably an important element in the marine environment. Its role as a limiting macronutrient for primary productivity inextricably links it to the global carbon cycle and thus the climate system over geologic time scales. However, there remain many unanswered questions or ambiguous answers to the global phosphorus cycle. Pinpointing the sources and sinks of this globally importan element remain elusive, and changes of either one could greatly alter the residence time of P in the ocean and thus, estimates of its contribution to carbon export throught ocean productivity, Furthermore, athropegenic inputs of P to the marine environment are greatly altering the source contibution of P, and the ultimate effects of these additions and how they will interact with anthropogenic inputs of nitrogen and other elements and, more importnatly, how they will affect marine ecosystmes are still largely unknown. With the advent of new techniques, we have gained a greater understanding of the forms of phosphorus in the marine environment and how specific organisms utilize each of these phosphorus pools. Major advances have been made not only in identifying the microorganisms which are active in the turnover of organic phosphorus compounds but also in identifying the genes which are involved in creating the enzymes that make this turnover possible. Furthermore, specific species have been identified which can utilize specific enzymes to access forms of P that were previously thought to be too recalcitrant to be biologically available. However, the time scales and the quantity of P turnover in this manner remain undefined. Consequently, despite the advancement in both knowledge and techniques available to understand the marine phosphorus cycle, we still have a long way to go before the cycle can be fully characterized. However, with the increased realization that the marine P cycle is more dynamic than previously thought, it is likely that more studies will focus on this element in the future.