Supraglacial discharge of limiting micronutrients such as iron (Fe) into high-nutrient low-chlorophyll (HNLC) regions like the Southern Ocean has recently drawn global attention. In this study, we aim to understand the contribution of cryoconite holes (comprising a meltwater column with an underlying layer of sediment) to the discharge of Fe through the glacier runoff. Cryoconite hole meltwater collected from the Larsemann Hills, East Antarctica showed a higher concentration of dissolved Fe (dFe: 71.2 μgL) and total Fe extractable from suspended sediments (exFe: 362.1 μgL) than in the adjacent streams (dFe: 30.5 μgL; exFe: 21.2 μgL) and melt pools (dFe: 42.3 μgL; exFe: 5.8 μgL). Predictive pathways (using PICRUSt2) show that cryoconite hole bacterial communities could acquire Fe and other trace elements using different mechanisms, such as the biosynthesis of siderophores, and transport proteins, therefore influencing the trace metal chemistry in these and other environments that drain cryoconite hole contents. Estimated discharge of dFe (11.4 kg km a) and exFe (57.9 kg km a) within cryoconite holes are 2 and 17 times higher, respectively than the discharge from the adjacent supraglacial streams, indicating that cryoconite holes are an important source of potentially bioavailable Fe to the HNLC region.

中文翻译：

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冰石洞对南极洲东部拉瑟曼山生物可利用铁的冰上排放的贡献

冰上向南大洋等高营养低叶绿素（HNLC）区域排放有限的微量营养素（例如铁（Fe））最近引起了全球的关注。在这项研究中，我们的目的是了解冰石洞（包括带有沉积物层的融水柱）对通过冰川径流排放铁的贡献。从东南极洲拉斯曼山收集的冰石洞融水显示，与邻近溪流（dFe：30.5 μgL；exFe： 21.2 μgL）和熔池（dFe：42.3 μgL；exFe：5.8 μgL）。预测途径（使用 PICRUSt2）表明，冰石孔细菌群落可以使用不同的机制（例如铁载体的生物合成和转运蛋白）获取 Fe 和其他微量元素，从而影响这些环境和其他排出冰石孔内容物的环境中的痕量金属化学。冰石洞内 dFe (11.4 kg km a) 和 exFe (57.9 kg km a) 的估计排放量分别比邻近冰上溪流的排放量高 2 倍和 17 倍，表明冰冰石洞是潜在生物可利用铁的重要来源到 HNLC 区域。