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Natural Fe-binding organic ligands in Fram Strait and over the northeast Greenland shelf
Marine Chemistry ( IF 3 ) Pub Date : 2020-05-01 , DOI: 10.1016/j.marchem.2020.103815
Indah Ardiningsih , Stephan Krisch , Pablo Lodeiro , Gert-Jan Reichart , Eric P. Achterberg , Martha Gledhill , Rob Middag , Loes J.A. Gerringa

There is a paucity of data on Fe-binding ligands in the Arctic Ocean. Here we investigate the distribution and chemical properties of natural Fe-binding ligands in Fram Strait and over the northeast Greenland shelf, shedding light on their potential sources and transport. Our results indicate that the main sources of organic ligands to surface waters of Fram Strait included primary productivity and supply from the Arctic Ocean. We calculated the mean total Fe-binding ligand concentration, [Lt], in Polar Surface Water from the western Fram Strait to be 1.65 ± 0.4 nM eq. Fe. This value is in between reported values for the Arctic and North Atlantic Oceans, confirming reports of north to south decreases in [Lt] from the Arctic Ocean. The differences between ligand sources in different biogeochemical provinces, resulted in distinctive ligand properties and distributions that are reflected in [Lt], binding strength (log KFe'L) and competing strength (log αFe'L) of ligands. Higher [Lt] was present near the Nioghalvfjerdsfjorden (79 N) Glacier terminus and in the Westwind Trough (median of [Lt] = 2.17 nM eq. Fe; log KFe'L = 12.3; log αFe'L = 3.4) than in the Norske Trough (median of [Lt] = 1.89 nM eq. Fe; log KFe'L= 12.8; log αFe'L = 3.8) and in Fram Strait (median of [Lt] = 1.38 nM eq. Fe; log KFe'L = 13; log αFe'L= 3.9). However, organic ligands near the 79 N Glacier terminus and in the Westwind Trough were weaker, and therefore less reactive than organic ligands in the Norske Trough and in Fram Strait. These weaker ligands, although more abundant than in the Fram Strait, reduce overall Fe solubility in waters transported from the 79N Glacier to Fram Strait. The lower ligand binding strength in the outflow results in a higher inorganic Fe concentration, [Fe´], which is more prone to precipitation and/or scavenging than Fe complexed with stronger ligands. Ongoing changes in the Arctic and sub-Arctic Oceans will influence both terrestrially derived and in-situ produced Fe-binding ligands, and therefore will have consequences for Fe solubility and availability to microbial populations and Fe cycling in Fram Strait.



中文翻译:

弗拉姆海峡和东北格陵兰架子上的天然铁结合有机配体

在北冰洋,关于铁结合配体的数据很少。在这里,我们研究了天然铁结合配体在弗拉姆海峡和东北格陵兰大陆架上的分布和化学性质,从而揭示了其潜在来源和运输。我们的结果表明,弗拉姆海峡表层水的有机配体的主要来源包括初级生产力和北冰洋的补给。我们计算出西弗拉姆海峡极地表水的平均总铁结合配体浓度[L t ]为1.65±0.4 nM eq。铁 该值介于北冰洋和北大西洋的报告值之间,从而证实了[L t]来自北冰洋。不同生物地球化学省份中配体来源之间的差异导致了独特的配体性质和分布,这些均反映在[L t ],结合强度(logķ'大号)和配体的竞争强度(logαFe'L)。Nioghalvfjerdsfjorden(79 N)冰川终点附近和西风海槽中存在较高的[L t ](中位[L t ] = 2.17 nM eq。Fe ; logķ'大号= 12.3; 日志α Fe'L = 3.4)比在挪威槽[L的(中值] = 1.89 nM的当量的Fe;日志ķ'大号= 12.8; 日志α Fe'L = 3.8),并在弗拉姆海峡[L的(中值] = 1.38 nM的当量的Fe;日志ķ'大号= 13; 日志α Fe'L= 3.9)。但是,在79 N冰川终点附近和西风海槽中的有机配体较弱,因此,其反应性比Norske海槽和Fram海峡中的有机配体低。这些较弱的配体尽管比在Fram海峡中富集得多,但会降低从79N冰川运输到Fram海峡的水中铁的整体溶解度。流出物中较低的配体结合强度会导致较高的无机Fe浓度[Fe´],这与与较强配体配合的Fe相比,更易于沉淀和/或清除。北冰洋和北冰洋的持续变化将影响陆生和就地产生的铁结合配体,因此将对铁的溶解度和微生物种群的可用性以及铁架海峡的铁循环产生影响。

更新日期:2020-05-01
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