Apatite weathering and the Phanerozoic phosphorus cycle

Despite widespread debate in the literature, there is still considerable un certainty concerning which nutrient ultimately controls marine net ecosyste m production (NEP) over geologic time, Geochemical arguments suggest that p hosphorus is the culprit. The weathering of apatite, the primary phosphorus sink in Earth's exosphere, controls long-term phosphorus availability. If phosphorus is the ultimate controlling nutrient over geologic time scales, then long-term marine NEP is coupled to the release of phosphorus from apat ite weathering, The most abundant apatite compositions found in nature are igneous fluorapatite and marine sedimentary carbonate fluorapatite, Sparse data exist on how these compositions dissolve under Earth's surface conditi ons, To demonstrate a need for these data and their application, we present a kinetic treatment of existing data, augmented by new results. We then us e these results in a weathering model designed to illustrate the control ex erted by temperature (via activation energy) and surface area on the phosph orus flux from apatite dissolution during the Phanerozoic, Our conclusion i s that activation energy, and hence temperature, and apatite surface area a re important parameters governing the phosphorus flux from apatite weatheri ng and therefore marine NEP during Phanerozoic time.