Phosphate is an essential macronutrient for all organisms with a key role in setting levels of marine primary productivity. Despite its importance for marine biogeochemical cycles and its role in shaping the evolution of marine organisms, the factors controlling phosphate bioavailability on geologic timescales remain poorly understood. Here we develop a statistical model of the coupled cycles of phosphate, carbon, oxygen and calcium to constrain the weathering-derived fluxes and seawater concentrations of phosphate through Phanerozoic time (541 million years ago to the present). Our model includes input parameters and time-dependent forcings derived from geologic and geochemical data. We find that the climate sensitivity of chemical weathering of the oceanic crust by low-temperature fluids exerts a first-order control on phosphate availability. Specifically, continental weathering is a source of the limiting nutrient phosphate, but seafloor weathering is considered to be a minor phosphate sink. Consequently, times in Earth history during which seafloor weathering constituted a large fraction of the total (seafloor + continental) weathering were also times during which phosphate influxes to and concentrations in the ocean were relatively low. Lower seawater phosphate levels during those times probably resulted in lower primary productivity and oceanic and atmospheric oxygen concentrations.

磷酸盐是所有生物体必需的常量营养素，在设定海洋初级生产力水平方面起着关键作用。尽管它对海洋生物地球化学循环很重要并且在塑造海洋生物的进化中发挥作用，但在地质时间尺度上控制磷酸盐生物利用度的因素仍然知之甚少。在这里，我们开发了磷酸盐、碳、氧和钙耦合循环的统计模型，以限制显生宙时期（5.41 亿年前到现在）风化引起的磷酸盐通量和海水浓度。我们的模型包括来自地质和地球化学数据的输入参数和随时间变化的强迫。我们发现，低温流体对海洋地壳化学风化的气候敏感性对磷酸盐可用性施加了一级控制。具体而言，大陆风化是限制营养磷酸盐的来源，但海底风化被认为是次要的磷酸盐汇。因此，在地球历史上，海底风化占总风化（海底+大陆）很大一部分的时期也是磷酸盐流入海洋和海洋中浓度相对较低的时期。那些时期较低的海水磷酸盐水平可能导致较低的初级生产力以及海洋和大气中的氧气浓度。在地球历史上，海底风化占总风化（海底+大陆）很大一部分的时期也是磷酸盐流入海洋和海洋中浓度相对较低的时期。那些时期较低的海水磷酸盐水平可能导致较低的初级生产力以及海洋和大气中的氧气浓度。在地球历史上，海底风化占总风化（海底+大陆）很大一部分的时期也是磷酸盐流入海洋和海洋中浓度相对较低的时期。那些时期较低的海水磷酸盐水平可能导致较低的初级生产力以及海洋和大气中的氧气浓度。