Nutrient utilization and diatom productivity changes in the low-latitude south-eastern Atlantic over the past 70 ka: response to Southern Ocean leakage
Nutrient utilization and diatom productivity changes in the low-latitude south-eastern Atlantic over the past 70 ka: response to Southern Ocean leakage
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DOI：
10.5194/cp-17-603-2021
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发表时间：
2021-03-09
影响因子：
4.3
通讯作者：
Pashley, Vanessa
中科院分区：
文献类型：
--
作者：
Hendry, Katharine;Romero, Oscar;Pashley, Vanessa
东部边界隆起（EBUs）是现代海洋中生物硅（蛋白石）埋藏的关键地点，代表着重要的生产性海岸系统，对海洋有机碳固定做出了巨大贡献。位于大西洋东南部低纬度的本格拉上升流系统（BUS）是主要的EBU之一，并受到营养丰富的南大洋沃茨的直接影响。过去的硅藻生产力的变化，通过时间的量化，在晚第四纪气候变化的反应，饲料到我们的理解EBU未来气候扰动的敏感性。硅循环的现有沉积物档案包括蛋白石埋葬通量，硅藻组合，蛋白石硅同位素变化（表示三角洲Si-30）。埋藏通量和硅质组合仅限于记录到达沉积物（即出口）的遗骸，和三角洲Si-30的变化是复杂的物种特异性的影响和季节性。在这里，我们提出了第一个结合三角洲Si-30记录的两个大型中心硅藻从总线，包括完整的冰川条件全新世。除了出口，我们的新数据使我们能够重建利用溶解硅在表面沃茨在南大洋沃茨强输入的地区。我们的新档案显示，有增强的南大洋富硅水上升流伴随着强烈的草酸利用沿海居住硅藻在海洋同位素阶段3（MIS 3; 60-40 ka）。这种脉冲的强酸性利用其次是减弱上升流和沿海硅藻硅利用到MIS 2，在整个冰消期增加远洋硅藻硅利用。我们将我们的研究结果与质量平衡模型实验相结合，表明地表水二氧化硅循环随时间的变化是上升流强度和利用率变化的函数，说明了EBU对冰川-间冰期尺度气候变化的敏感性。
Eastern boundary upwellings (EBUs) are some of the key loci of biogenic silica (opal) burial in the modern ocean, representing important productive coastal systems that extraordinarily contribute to marine organic carbon fixation. The Benguela upwelling system (BUS), in the low-latitude south-eastern Atlantic, is one of the major EBUs and is under the direct influence of nutrient-rich Southern Ocean waters. Quantification of past changes in diatom productivity through time, in response to late Quaternary climatic change, feeds into our understanding of the sensitivity of EBUs to future climatic perturbations. Existing sediment archives of silica cycling include opal burial fluxes, diatom assemblages, and opaline silicon isotopic variations (denoted by delta Si-30). Burial fluxes and siliceous assemblages are limited to recording the remains reaching the sediment (i.e. export), and delta Si-30 variations are complicated by species-specific influences and seasonality. Here, we present the first combined delta Si-30 record of two large centric diatoms from the BUS, encompassing full glacial conditions to the Holocene. In addition to export, our new data allow us to reconstruct the utilization of dissolved Si in surface waters in an area with strong input from Southern Ocean waters. Our new archives show that there was enhanced upwelling of Southern Ocean Si-rich water accompanied by strong silicic acid utilization by coastal dwelling diatoms during Marine Isotope Stage 3 (MIS3; 60-40 ka). This pulse of strong silicic acid utilization was followed by a weakening of upwelling and coastal diatom Si utilization into MIS2, before an increase in pelagic diatom Si utilization across the deglaciation. We combine our findings with mass balance model experiments to show that changes in surface water silica cycling through time are a function of both upwelling intensity and utilization changes, illustrating the sensitivity of EBUs to climatic change on glacial-interglacial scales.