Abstract Manganese (Mn) is an essential micronutrient for phytoplankton and its cycling interacts with that of iron (Fe). Continental shelf sediments are a key but poorly quantified source of Mn to marine waters. In this study, we investigate Mn release from shelf sediments, its lateral transport (“shuttling”) in the oxic water column over the northwestern Black Sea shelf and its fate in the adjacent euxinic deep basin. We find a high release of Mn from organic-rich, bioirrigated coastal sediments, but negligible mobilization and release of Mn from sediments in offshore shelf regions, because of a low input of organic matter. Most Mn in the water column is present in dissolved form. We suggest that this dissolved Mn is released from coastal sediments and subsequently transported offshore through physical processes. Surface sediments at open shelf and shelf edge stations are highly enriched in Mn when compared to coastal and deep basin stations. Only part of the surface enrichment can be explained by oxidation of porewater Mn. The remainder of this enrichment is likely the result of oxidative removal of dissolved Mn from the water column and deposition as Mn oxides. Using X-ray spectroscopy we show that Mn in surface sediments in this area predominately consists of Mn(IV) oxides (phyllo- and/or tectomanganates). A key difference between Mn versus Fe shuttling is the form in which the metal is transported: while dissolved Mn dominates in the water column over the shelf, most Fe is present in particulate form. Sediment trap data indicate that the vertical transport of both Mn and Fe through the euxinic water column is correlated and is associated with the sinking flux of biogenic particulate matter following the spring and fall phytoplankton blooms. In the sediments of the euxinic basin, Mn is enriched when compared to a detrital Mn background and its burial correlates with that of Fe. This suggests that Mn could be incorporated in pyrite in the euxinic water column. Our results highlight the critical role of organic matter input as a driver of Mn and Fe shuttling over the Black Sea continental shelf and particulate matter as the carrier of Mn and Fe into the euxinic basin.

中文翻译：

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锰在黑海大陆架西北部穿梭的控制及其在富生深盆地中的归宿

摘要 锰 (Mn) 是浮游植物必需的微量营养素，其循环与铁 (Fe) 的循环相互作用。大陆架沉积物是海水中锰的关键但量化不足的来源。在这项研究中，我们调查了大陆架沉积物中锰的释放、其在黑海大陆架西北部的含氧水体中的横向迁移（“穿梭”）及其在相邻的富氧深盆中的归宿。我们发现富含有机物的生物灌溉沿海沉积物中锰的大量释放，但由于有机质输入量低，近海陆架地区沉积物中锰的迁移和释放可以忽略不计。水柱中的大部分锰以溶解形式存在。我们认为，这种溶解的锰从沿海沉积物中释放出来，随后通过物理过程输送到近海。与沿海和深盆站相比，开放式陆架和陆架边缘站的表层沉积物富含锰。只有部分表面富集可以用孔隙水 Mn 的氧化来解释。这种富集的其余部分可能是从水柱中氧化去除溶解的 Mn 并作为 Mn 氧化物沉积的结果。使用 X 射线光谱，我们表明该区域表层沉积物中的 Mn 主要由 Mn(IV) 氧化物（叶状和/或 tectomanganates）组成。Mn 与 Fe 穿梭之间的主要区别在于金属的运输形式：虽然溶解的 Mn 在架子上的水柱中占主导地位，但大多数 Fe 以颗粒形式存在。沉积物捕集器数据表明，Mn 和 Fe 通过 euxinic 水柱的垂直传输是相关的，并且与春季和秋季浮游植物大量繁殖后生物颗粒物质的下沉通量有关。在 euxinic 盆地的沉积物中，与碎屑 Mn 背景相比，Mn 富集，其埋藏与 Fe 的埋藏相关。这表明 Mn 可以掺入富氧水柱中的黄铁矿中。我们的研究结果强调了有机质输入作为锰和铁在黑海大陆架上穿梭的驱动因素和颗粒物质作为锰和铁进入优生盆地的载体的关键作用。与碎屑 Mn 背景相比，Mn 富集，其埋藏与 Fe 的埋藏相关。这表明 Mn 可以掺入富氧水柱中的黄铁矿中。我们的研究结果强调了有机质输入作为锰和铁在黑海大陆架上穿梭的驱动因素和颗粒物质作为锰和铁进入优生盆地的载体的关键作用。与碎屑 Mn 背景相比，Mn 富集，其埋藏与 Fe 的埋藏相关。这表明 Mn 可以掺入富氧水柱中的黄铁矿中。我们的研究结果强调了有机质输入作为锰和铁在黑海大陆架上穿梭的驱动因素和颗粒物质作为锰和铁进入优生盆地的载体的关键作用。