Seasonal ITCZ migration dynamically controls the location of the (sub)tropical Atlantic biogeochemical divide.
Seasonal ITCZ migration dynamically controls the location of the (sub)tropical Atlantic biogeochemical divide.
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季节性 ITCZ 迁移动态控制（亚）热带大西洋生物地球化学分水岭的位置。
DOI：
10.1073/pnas.1318670111
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发表时间：
2014
影响因子：
11.1
通讯作者：
Schlosser C
中科院分区：
文献类型：
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作者：
Schlosser C
无机氮消耗限制了大部分低纬度海洋的生产力，为能够固定大气二氮（N2）的固氮生物产生了选择性优势。然而，固氮生物的丰度和活性反过来又可以通过其他潜在限制性营养物质的可用性来控制，包括磷 (P) 和铁 (Fe)。在这里，我们提供了溶解铁、铝和无机磷的高分辨率数据（∼0.3°），证实（亚）热带大西洋表面营养物浓度存在明显的南北生物地球化学边界。结合卫星降水数据和之前的研究结果，我们证明热带辐合带区域的湿沉降是地表水的主要溶解铁源。此外，还对固氮和固氮Trichodesmiumspp 的分布进行了相应的观察。表明由于热带辐合带的季节性迁移而导致溶解铁升高的区域的移动驱动了重氮化物的纬度分布的变化和相应的溶解无机磷的消耗。这些结论与系统理想化数值模型的结果一致。因此，（亚）热带大西洋不同生物地球化学系统之间的边界似乎是由对外部铁输入的时空变化的固氮响应来定义的。因此，除了证明大气养分输入所迫使的独特季节性周期之外，我们认为潜在的生物地球化学机制可能会表征寡营养系统在较长时间尺度上对改变的环境强迫的响应。
Inorganic nitrogen depletion restricts productivity in much of the low-latitude oceans, generating a selective advantage for diazotrophic organisms capable of fixing atmospheric dinitrogen (N2). However, the abundance and activity of diazotrophs can in turn be controlled by the availability of other potentially limiting nutrients, including phosphorus (P) and iron (Fe). Here we present high-resolution data (∼0.3°) for dissolved iron, aluminum, and inorganic phosphorus that confirm the existence of a sharp north–south biogeochemical boundary in the surface nutrient concentrations of the (sub)tropical Atlantic Ocean. Combining satellite-based precipitation data with results from a previous study, we here demonstrate that wet deposition in the region of the intertropical convergence zone acts as the major dissolved iron source to surface waters. Moreover, corresponding observations of N2fixation and the distribution of diazotrophicTrichodesmiumspp. indicate that movement in the region of elevated dissolved iron as a result of the seasonal migration of the intertropical convergence zone drives a shift in the latitudinal distribution of diazotrophy and corresponding dissolved inorganic phosphorus depletion. These conclusions are consistent with the results of an idealized numerical model of the system. The boundary between the distinct biogeochemical systems of the (sub)tropical Atlantic thus appears to be defined by the diazotrophic response to spatial–temporal variability in external Fe inputs. Consequently, in addition to demonstrating a unique seasonal cycle forced by atmospheric nutrient inputs, we suggest that the underlying biogeochemical mechanisms would likely characterize the response of oligotrophic systems to altered environmental forcing over longer timescales.