Fluxes of particulate iron from the upper ocean around the Crozet Islands: A naturally iron‐fertilized environment in the Southern Ocean
Fluxes of particulate iron from the upper ocean around the Crozet Islands: A naturally iron‐fertilized environment in the Southern Ocean
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克罗泽群岛周围上层海洋的颗粒铁通量：南大洋的天然铁肥环境
DOI：
10.1029/2010gb003789
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发表时间：
2011
影响因子：
5.2
通讯作者：
G. Fones
中科院分区：
文献类型：
--
作者：
H. Planquette;R. Sanders;P. Statham;P. Morris;G. Fones
尽管有大量的常量营养素库，南大洋的叶绿素水平低，主要是由于铁的可用性低。与这种情况类似的是岛屿系统，在那里天然陆地铁的输入允许大水华的发展。颗粒有机碳（POC）和颗粒（不稳定和难熔）铁的分析进行了大（>53 μm）的颗粒收集在这样一个系统（克罗泽群岛）的混合层的基础上，并在邻近的高营养，低叶绿素（HNLC）沃茨。生物铁通过从总铁中去除估计的石生铁而获得。我们结合联合收割机这些数据与234 Th测量，以确定向下的颗粒Fe通量。铁的通量范围为4 ~ 301 nmol m−2 d−1（不稳定），不可检测到50 μmol m−2 d−1（生物源），3 ~ 145 μmol m−2 d−1（总），平均而言，高产、自然铁肥化区域下方的铁通量大约是相邻HNLC区域下方的4倍。向下的不稳定铁通量接近于根据Planquette等人（2007年）模型计算的陆地溶解铁、大气溶解铁和涌上铁的总和。难熔的铁通量要大200 - 200个数量级，这些只能来自高原本身平流的粒子。生物铁占岛屿北部颗粒铁总量的很大一部分（0- 76%，平均23%）。这个铁池的起源必须占主导地位的生物转化从成岩部分，其他供应条款，包括风成，深层混合，溶解铁和横向平流是不足以占这个铁的大小。因此，需要将成岩铁通量的近海生物可利用部分包括在内，以充分计算每单位注入铁的碳输出量。
Despite a large macronutrient reservoir, the Southern Ocean has low levels of chlorophyll, primarily due to low iron availability. Exceptions to this situation are island systems where natural terrestrial iron inputs allow the development of large blooms. Particulate organic carbon (POC) and particulate (labile and refractory) iron analyses were performed on large (>53 μm) particles collected at the base of the mixed layer within such a system (the Crozet Islands) and in adjacent high‐nutrient, low‐chlorophyll (HNLC) waters. Biogenic iron was obtained by removal of estimated lithogenic Fe from the total Fe present. We combine these data with 234Th measurements to determine downward particulate Fe fluxes. Fluxes of Fe ranged from 4 to 301 nmol m−2 d−1 (labile), not detectable to 50 μmol m−2 d−1 (biogenic), and from 3 to 145 μmol m−2 d−1 (total) and, on average, were approximately four times larger below the highly productive, naturally iron‐fertilized region than below the adjacent HNLC area. Downward labile iron fluxes are close to the sum of dissolved terrestrial, atmospheric, and upwelled iron calculated from the Planquette et al. (2007), model. Refractory iron fluxes are ∼2 orders of magnitude larger, and these can only have come from particles advected from the plateau itself. The “biogenic Fe,” is a substantial fraction (0–76, mean 23%) of the total particulate Fe to the north of the islands. The origin of this Fe pool must be dominantly biological conversion from the lithogenic fraction, as other supply terms including aeolian, deep mixing, and lateral advection of dissolved Fe are inadequate to account for the magnitude of this Fe. Inclusion of the offshore biologically available fraction of the lithogenic iron flux is therefore required to calculate fully the yield of carbon exported per unit iron injected.