Abstract Both bioavailable iron (Fe) and water stability have been proposed to regulate primary production in large parts of the Southern Ocean. Freshwater is not only an important factor regulating water stability, but is also an important source of dissolved iron (DFe) for phytoplankton growth. In this study, stable oxygen isotopic composition (δ18O) and salinity were used to distinguish meteoric water (glacial discharge and precipitation) from sea ice meltwater in the northernmost part of the eastern Antarctic Peninsula (eAP). The carbon fixation rate (CFR) and Fe uptake rate (FeUR) were measured via 14C and 55Fe tracer assay, respectively. We observed positive responses of FeURs to the fraction of meteoric water and sea ice meltwater, and a stronger correlation between FeUR and meteoric water, indicating that freshwater input could relieve the Fe limitation in this area, and meteoric water was likely to be the main source of DFe. In addition, we also observed that both meteoric water and sea ice meltwater increased CFR, but CFR only showed slightly positive response to sea ice meltwater. This suggested that the primary effect of increased sea ice meltwater was to enhance the stability of water column, providing a favorable condition for phytoplankton growth. Since the potential meteoric water inventory is much greater than sea ice meltwater and meteoric water input is expected to rise further as climate warming continues as mentioned in Meredith et al’s studies (2008, 2010), the meteoric water is likely increasingly important in Antarctic coastal zones. Smaller phytoplankton responded more obviously to the freshwater input, and we speculate that this would influence on the carbon export in the ambient and nearby oceanic areas. The low Fe demand (Fe:C ratio = 8.04 μmol mol−1) suggested that phytoplankton in the eAP were adapted to a low Fe environment. In addition, primary production estimated from high Fe:C ratios would underestimate the real situation in the southern ocean. These findings help to understand how meteoric water and sea ice meltwater could affect the Antarctic ecosystem in response to climate change.

中文翻译：

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流星水促进南极半岛东端浮游植物的碳固定和铁吸收 (eAP)

摘要 生物可利用铁 (Fe) 和水稳定性已被提议用于调节南大洋大部分地区的初级生产。淡水不仅是调节水体稳定性的重要因素，也是浮游植物生长溶解铁（DFe）的重要来源。在这项研究中，稳定的氧同位素组成（δ18O）和盐度被用来区分南极半岛东部（eAP）最北端的大气水（冰川排放和降水）与海冰融水。碳固定率 (CFR) 和铁吸收率 (FeUR) 分别通过 14C 和 55Fe 示踪剂测定进行测量。我们观察到 FeURs 对大气水和海冰融水的比例有积极的反应，并且 FeUR 和大气水之间的相关性更强，表明淡水输入可以缓解该地区的 Fe 限制，而大气水可能是 DFe 的主要来源。此外，我们还观察到大气水和海冰融水都增加了 CFR，但 CFR 仅对海冰融水表现出轻微的积极反应。这表明海冰融水增加的主要作用是增强了水体的稳定性，为浮游植物的生长提供了有利条件。由于潜在的大气水存量远大于海冰融水，并且如 Meredith 等人的研究（2008 年、2010 年）所述，随着气候变暖的持续，大气水输入预计将进一步增加，因此大气水在南极沿海地区可能越来越重要. 较小的浮游植物对淡水输入的反应更明显，我们推测这会影响周围和附近海洋区域的碳输出。低铁需求（铁碳比 = 8.04 μmol mol-1）表明 eAP 中的浮游植物适应了低铁环境。此外，根据高铁碳比估算的初级产量会低估南大洋的实际情况。这些发现有助于了解大气水和海冰融水如何影响南极生态系统以应对气候变化。