Diatom Physiology Controls Silicic Acid Leakage in Response to Iron Fertilization
Diatom Physiology Controls Silicic Acid Leakage in Response to Iron Fertilization
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DOI：
10.1029/2019gb006460
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发表时间：
2019-12
影响因子：
5.2
通讯作者：
M. Holzer;B. Pasquier;T. DeVries;M. Brzezinski
中科院分区：
文献类型：
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作者：
M. Holzer;B. Pasquier;T. DeVries;M. Brzezinski
我们探讨了硅藻的 Si:P 吸收比率 RSi:P 的铁依赖性如何控制全球硅循环和浮游植物群落结构对南大洋铁施肥的响应。我们使用耦合 Si-P-Fe 循环的数据约束模型，该模型具有三个浮游植物类别的营养物共同限制的机械表示，并且嵌入数据同化的全球海洋环流模型中。我们考虑了RSi:P对铁依赖性的三个参数化，所有这些参数都与现有的现场数据一致，并且同样能够很好地拟合观测到的营养气候学，但会导致对铁施肥的非常不同的反应：根据RSi:P随着铁浓度的增加而急剧下降的程度，铁施肥可能会导致南大洋硅酸泄漏增加或南大洋硅捕获加强。如果RSi:P的减少战胜了硅藻生长的增加，硅酸泄漏就会增加，反之则会导致南大洋硅捕获的加强。硅酸泄漏导致亚热带环流中的植物区系向有利于硅藻的方向转变，并刺激低纬度蛋白石出口的增加。硅藻对全球磷出口的贡献增加，但铁充足条件下硅藻硅需求量较低，减少了全球蛋白石出口。无论RSi:P参数化如何，生物磷和硅泵的全球响应以南大洋为主。随着铁引起的硅酸泄漏的增加，蛋白石通量的硅同位素特征系统地变轻，这与富铁冰川期的沉积物记录一致。
We explore how the iron dependence of the Si:P uptake ratio RSi:P of diatoms controls the response of the global silicon cycle and phytoplankton community structure to Southern Ocean iron fertilization. We use a data‐constrained model of the coupled Si‐P‐Fe cycles that features a mechanistic representation of nutrient colimitations for three phytoplankton classes and that is embedded in a data‐assimilated global ocean circulation model. We consider three parameterizations of the iron dependence of RSi:P, all of which are consistent with the available field data and allow equally good fits to the observed nutrient climatology but result in very different responses to iron fertilization: Depending on how sharply RSi:P decreases with increasing iron concentration, iron fertilization can either cause enhanced silicic acid leakage from the Southern Ocean or strengthened Southern Ocean silicon trapping. Enhanced silicic acid leakage occurs if decreases in RSi:P win over increases in diatom growth, while the converse causes strengthened Southern Ocean silicon trapping. Silicic acid leakage drives a floristic shift in favor of diatoms in the subtropical gyres and stimulates increased low‐latitude opal export. The diatom contribution to global phosphorus export increases, but the lower diatom silicon requirement under iron‐replete conditions reduces the global opal export. Regardless of RSi:P parameterization, the global response of the biological phosphorus and silicon pumps is dominated by the Southern Ocean. The Si isotope signature of opal flux becomes systematically lighter with increasing iron‐induced silicic acid leakage, consistent with sediment records from iron‐rich glacial periods.