Recycling of dissolved iron in the North Pacific Subtropical Gyre
Recycling of dissolved iron in the North Pacific Subtropical Gyre
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DOI：
10.1002/lno.12212
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发表时间：
2022-09
影响因子：
4.5
通讯作者：
N. Hawco;Shun‐Chung Yang;P. Pinedo‐González;Erin E. Black;J. Kenyon;S. Ferrón;X. Bian;S. John
中科院分区：
文献类型：
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作者：
N. Hawco;Shun‐Chung Yang;P. Pinedo‐González;Erin E. Black;J. Kenyon;S. Ferrón;X. Bian;S. John
铁作为开阔海洋中的限制性营养素的重要性已得到广泛承认，但它在海洋环境中的循环速率存在很大的不确定性。在这里，我们结合联合收割机测量水柱，沉积物陷阱，孵化器，以限制铁周转在夏季站ALOHA在北太平洋副热带环流。使用低水平的57 Fe-58 Fe双尖峰，通过多收集器电感耦合等离子体质谱法高精度测量，我们发现整个真光层的Fe吸收率为30-60 pM d−1。溶解铁周转时间估计为10-15 d的混合层和1-3 d附近的深层叶绿素最大值。从钍同位素质量平衡推断的气溶胶Fe供应表明，溶解的Fe停留时间约为6个月，在上部真光层（0-75米），相对于外部来源，和2个月，在下部真光层（75-150米）。为了协调这些观测结果，在ALOHA站的上透光层和下透光层中，平均Fe原子必须循环25次以上（“Fe比率”分别等于0.04和0.03），到目前为止，只有在Fe有限的区域才有记录。在稳定状态下，这种情况下需要的气溶胶铁溶解度为4.5%，这是类似的溶解实验从太平洋气溶胶。我们的研究结果表明，贫营养海洋能够有效地回收铁，即使这些生态系统没有明显的铁限制。
The importance of iron as a limiting nutrient in the open ocean is widely recognized, but there is substantial uncertainty about the rate that it cycles in the marine environment. Here, we combine measurements from the water column, sediment traps, and incubations to constrain Fe turnover during summer at Station ALOHA in the North Pacific Subtropical Gyre. Using low levels of 57Fe–58Fe double spike, measured with high precision by multi‐collector inductively coupled plasma mass spectrometry, we find Fe uptake rates of 30–60 pM d−1 throughout the euphotic zone. Dissolved Fe turnover times are estimated at 10–15 d in the mixed layer and 1–3 d near the deep chlorophyll maximum. Aerosol Fe supply inferred from a thorium isotope mass balance indicates that the dissolved Fe residence time is approximately 6 months in the upper euphotic zone (0–75 m), relative to external sources, and 2 months in the lower euphotic zone (75–150 m). To reconcile these observations, the average Fe atom must be recycled over 25 times at Station ALOHA in both the upper and lower euphotic zones (an “Fe ratio” equal to 0.04 and 0.03, respectively), a level of conservation that has only been documented in Fe‐limited regions thus far. At steady state, this scenario requires an aerosol Fe solubility of 4.5%, which is similar to dissolution experiments from Pacific Ocean aerosols. Our results suggest that the oligotrophic ocean is capable of recycling iron efficiently even when these ecosystems are not demonstrably iron‐limited.