To assess the impacts of Amazon River discharge, Saharan dust deposition, N2-fixation and mixed-layer deepening on the biological carbon pump, sediment traps were moored from October 2012 to November 2013 at two sites in the western tropical North Atlantic (49°W,12°N/57°W,12°N). Particle exports interpreted along with satellite- and Argo-float data show peak fluxes in biogenic silica (31 mg m−2 d−1) and organic carbon (25 mg m−2 d−1) during the fall of 2013 that were ten to five times higher than any time earlier during the year. These high export fluxes occurred in tandem with high surface chlorophyll a concentrations associated with the dispersal of the Amazon River plume, following retroflection into the North-Atlantic-Counter-Current. High fucoxanthin fluxes (' 80 μg m−2 d−1) and low δ15N-values (−0.6‰) suggest a large contribution by marine diatom-diazotrophic-associations, possibly enhanced by wet Saharan dust deposition. During summer, the Amazon River plume resulted in high mass fluxes at 57°W that were enriched in biogenic silica but weakly influenced by diazotrophic-associations compared to the fall event at 49°W. High carbonate-carbon fluxes (17 mg m−2 d−1) dominated a second single event at 49°W during spring that was likely triggered by mixed-layer deepening. Rain-ratios of BSi/Ccarb amounted to 1.7 when associated with high export fluxes linked to the Amazon River plume. Compared to an annual average of 0.3, this indicates a more efficient uptake of CO2 via the biological pump compared to when the plume was absent, hence supporting earlier observations that the Amazon River plume is important for ocean CO2 sequestration.

中文翻译：

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西热带北大西洋生产和颗粒出口的多重驱动因素

为了评估亚马逊河排放、撒哈拉尘埃沉积、N2 固定和混合层加深对生物碳泵的影响，2012 年 10 月至 2013 年 11 月期间，在热带北大西洋西部（49°W）的两个地点停泊了沉积物捕集器。 ,12°N/57°W,12°N)。与卫星和 Argo 浮点数据一起解释的粒子出口显示 2013 年秋季生物二氧化硅（31 mg m-2 d-1）和有机碳（25 mg m-2 d-1）的峰值通量为 10 到比今年早些时候任何时候都高出五倍。这些高出口通量与亚马逊河羽流扩散相关的高表面叶绿素 a 浓度同时发生，在逆反射进入北大西洋逆流之后。高岩藻黄质通量 (' 80 μg m-2 d-1) 和低 δ15N 值 (-0. 6‰) 表明海洋硅藻 - 固氮 - 关联的巨大贡献，可能由湿撒哈拉尘埃沉积增强。在夏季，亚马逊河羽流在 57°W 产生高质量通量，富含生物二氧化硅，但与 49°W 的秋季事件相比，受固氮关联的影响较弱。春季期间在 49°W 的第二个单一事件中，高碳酸盐-碳通量（17 mg m-2 d-1）占主导地位，这可能是由混合层加深引发的。当与亚马逊河羽流相关的高出口通量相关时，BSi/Ccarb 的降雨比达到 1.7。与年平均值 0.3 相比，这表明与没有羽流时相比，通过生物泵更有效地吸收了 CO2，因此支持早期的观察，即亚马逊河羽流对海洋 CO2 封存很重要。