The deep basins of the Baltic Sea experienced dramatic climate- and eutrophication-induced redox changes between oxic and euxinic water column conditions. Irregularly appearing Major Baltic Inflows (MBI) carrying North Sea waters to the Baltic Sea are partly able to oxygenate euxinic bottom waters within several weeks. After an absence of ~10 years, an exceptional strong inflow event in December 2014 reached the Gotland Basin in early March 2015 providing the opportunity of detailed studies on the impact of fast redox shifts on elemental cycles. Here we report on P and trace metal (Co, Mo, U, V and W) dynamics in the water column, pore water, and sediment of the central Gotland Basin over a 4.5 year-long observation period. These time series record the entire redox development including the primary MBI-related oxygenation, the transitional development to anoxia before a second inflow pulse, and the final re-establishment of euxinia. Samples obtained in August 2012 represent the previous euxinic stagnation period not affected by MBI's since nearly a decade. Concentration measurements and a budget calculation suggest only a limited impact of the MBI on the water column P inventory and the corresponding eutrophication level of the Gotland Basin. This is due to insufficient Fe availability preventing efficient trapping of phosphate during water column oxygenation. In addition, the fast recovery of reducing conditions allowed only a short-term storage of deposited Mn–Fe–P mineral phases in the surface sediment. Due to pronounced scavenging by Mn oxides, substantial water column depletion occurred intermittently for V and W, but again, re-establishing reducing conditions favored Mn oxide dissolution and the release especially of W back into the water column. Mo and U were less affected by Mn and Fe shuttling and Mo even showed an increasing water column inventory due to replenishment by intruding North Sea waters. In contrast, the water column inventory of Co remained on an approx. 50% level about 4.5 years after the inflow suggesting a significant sedimentary burial of Co within the course of the inflow event. Although sedimentary Mn carbonate layers, which were commonly formed in concert with the frequent inflows between ~1960 and 1980, were missing or only weakly developed after the single inflow events in 1994, 2003, and 2014, dated short cores from the study area reveal clear Co and less pronounced V enrichments during the latter inflows. Because Mo, U and W are synchronously depleted compared with their normal sapropel levels, the combination of these trace metals and Co may help to identify past MBIs not reflected by Mn carbonate presence.

波罗的海深海盆地在富氧和富氧水柱条件之间经历了由气候和富营养化引起的剧烈氧化还原变化。将北海水带入波罗的海的不规则出现的主要波罗的海流入量（MBI）能够在几周内将富氧的底部水氧化。经过约10年的时间，2014年12月发生了一次异常强烈的流入事件，于2015年3月上旬到达哥得兰盆地，为进一步研究快速氧化还原变化对元素周期的影响提供了机会。在这里，我们报告了在长达4.5年的观察期内中部哥得兰盆地水柱，孔隙水和沉积物中的P和痕量金属（Co，Mo，U，V和W）动力学。这些时间序列记录了整个氧化还原的发展，包括与MBI相关的主要氧合，在第二次流入脉冲之前向缺氧的过渡发展，并最终重新建立了游刃有余的状态。2012年8月获得的样本代表了过去近十年以来不受MBI影响的先前的共济失调时期。浓度测量和预算计算表明，MBI仅对水柱P存量和哥得兰盆地的相应富营养化水平产生有限的影响。这是由于铁的利用率不足，阻止了水柱氧合过程中磷酸盐的有效捕集。此外，还原条件的快速恢复只能在表层沉积物中短期存储沉积的Mn-Fe-P矿物相。由于Mn氧化物的明显清除作用，V和W间歇性地发生了水柱的大量消耗，但同样，重新建立还原条件有利于Mn氧化物的溶解，尤其是W释放回水柱中。Mo和U受Mn和Fe穿梭的影响较小，并且Mo甚至显示出由于入侵北海水补充水柱而增加了水柱的存量。相比之下，Co的水柱存量保持在约5％。流入后约4.5年的水平为50％，表明在流入事件过程中大量的Co被沉积。尽管通常与1960年至1980年之间的频繁流入共同形成的沉积碳酸锰层，在1994年，2003年和2014年单次流入事件之后，缺失或仅发育较弱，但研究区的短岩心显示清楚在后面的流入过程中，Co和不太明显的V富集。因为莫