Organic ligands play a key role in the marine biogeochemical cycle of copper (Cu), a bio-essential element, regulating its solubility and bioavailability. However, the sources, abundance, and distribution of these ligands are still poorly understood. In this study, we examined vertical Cu speciation profiles from the South-East Atlantic (GEOTRACES section GA08). Profiles were collected from a range of ocean conditions, including the Benguela upwelling region, the oligotrophic South Atlantic Gyre, and the Congo River outflow. In general, the lack of a significant correlation between most of the parameters assessed here with Cu speciation data obscures the provenance of Cu-binding ligands, suggesting that Cu speciation in the South-East Atlantic is influenced by a complex interplay between biotic and abiotic processes. Nevertheless, the total dissolved Cu (Cu_T) illustrated an allochthonous origin in the working area, while Cu-binding ligands showed both an allochthonous and a biogenic, autochthonous origin. Pigment concentrations showed that the phylogeography of different microorganisms influenced the spatial features of the Cu-binding ligand pool in the South-East Atlantic. Allochthonous Cu-binding ligand sources in the upper water column are likely associated with dissolved organic matter which originated from the Congo River and the Benguela upwelling system. Deep water ligand sources could include refractory dissolved organic carbon (DOC), resuspended benthic inputs, and lateral advected inputs from the shelf margin. The degradation of L₁-type ligands and/or siderophores in low oxygen conditions may also be a source of L₂-type ligands in the deep. Free Cu ion levels (1.7 to 156 fM), the biologically available form of Cu_T, were below the putative biolimiting threshold of many marine organisms. Two classes of ligands were found in this study with total ligand concentrations ([L_T]) ranging from 2.5 to 283.0 nM and conditional stability constants (logK_{CuL, Cu2+}^cond) ranging from 10.7 to 14.6. The Cu speciation values were spatially variable across the three subregions, suggesting that biogeochemical processes and sources strongly influence Cu speciation.

有机配体在铜 (Cu) 的海洋生物地球化学循环中起着关键作用，铜是一种生物必需元素，可调节其溶解度和生物利用度。然而，这些配体的来源、丰度和分布仍然知之甚少。在这项研究中，我们检查了东南大西洋（GEOTRACES 部分 GA08）的垂直铜形态分布。从一系列海洋条件收集剖面，包括本格拉上升流区域、贫营养的南大西洋环流和刚果河流出。一般来说，这里评估的大多数参数与 Cu 形态数据之间缺乏显着相关性，这掩盖了 Cu 结合配体的来源，这表明东南大西洋的 Cu 形态受到生物和非生物过程之间复杂相互作用的影响. 尽管如此，_T ) 说明了工作区域中的异源起源，而 Cu 结合配体显示了异源和生物、本地起源。色素浓度表明，不同微生物的系统地理学影响了东南大西洋铜结合配体库的空间特征。上部水柱中的外来铜结合配体来源可能与源自刚果河和本格拉上升流系统的溶解有机物质有关。深水配体来源可能包括难熔溶解有机碳 (DOC)、重新悬浮的底栖输入和来自陆架边缘的横向平流输入。L ₁型配体和/或铁载体在低氧条件下的降解也可能是 L ₂的来源型配体在深处。游离铜离子水平（1.7 至 156 fM）是 Cu _T的生物可利用形式，低于许多海洋生物的假定生物限制阈值。在本研究中发现了两类配体，总配体浓度 ([L _T ]) 范围为 2.5 至 283.0 nM，条件稳定性常数 (log K _CuL，Cu2+ ^cond ) 范围为 10.7 至 14.6。三个子区域的铜形态值在空间上是可变的，这表明生物地球化学过程和来源强烈影响铜形态。