Holocene Refreshening and Reoxygenation of a Bothnian Sea Estuary Led to Enhanced Phosphorus Burial
Holocene Refreshening and Reoxygenation of a Bothnian Sea Estuary Led to Enhanced Phosphorus Burial
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DOI：
10.1007/s12237-017-0262-x
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发表时间：
2018-01-01
影响因子：
2.7
通讯作者：
Slomp, Caroline P.
中科院分区：
文献类型：
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作者：
Dijkstra, Nikki;Krupinski, Nadine B. Quintana;Slomp, Caroline P.
波罗的海等受限制盆地的盐度变化可能改变其对缺氧的脆弱性（即底部水氧浓度< 2毫克/升），并可能影响磷(P)的埋藏，磷是海洋生物的关键营养物质。我们结合孔隙水和固相地球化学，筛分沉积物的微观分析（包括XRD和基于同步加速器的XAS），以及有孔虫三角洲O-18和三角洲C-13分析，重建了波希尼亚海ngermanalven河口的底部水盐度、氧化还原条件和P埋藏。我们的沉积物记录是在2013年综合海洋钻探计划（IODP）波罗的海古环境考察347期间检索的。研究表明，在全新世早期海水入侵后，恩德曼阿尔文河口的底部水域出现了缺氧现象，与波斯尼亚海中部的情况类似。逐渐均衡隆起引起的更新和再氧化作用促进了富锰橄榄岩形式的P埋藏。河口较孤立部分的表层沉积物中薇薇石的自生作用最终停止，可能是由于持续的更新和相关的沉积物生产力和磷供应的下降。观测到的环境条件的变化也为自生橄榄石的沉积后形成创造了条件，可能形成磷灰石，在类似8 m的复合深度。这些与盐度相关的氧化还原条件和P埋藏变化与当前气候变化密切相关。结果特别强调，与全球变暖相关的淡水投入增加可能会增加沿海P的保留，从而导致沿海和邻近开放水域的少营养化。
Salinity variations in restricted basins like the Baltic Sea can alter their vulnerability to hypoxia (i.e., bottom water oxygen concentrations < 2 mg/l) and can affect the burial of phosphorus (P), a key nutrient for marine organisms. We combine porewater and solid-phase geochemistry, micro-analysis of sieved sediments (including XRD and synchrotron-based XAS), and foraminiferal delta O-18 and delta C-13 analyses to reconstruct the bottom water salinity, redox conditions, and P burial in the ngermanalven estuary, Bothnian Sea. Our sediment records were retrieved during the Integrated Ocean Drilling Program (IODP) Baltic Sea Paleoenvironment Expedition 347 in 2013. We demonstrate that bottom waters in the ngermanalven estuary became anoxic upon the intrusion of seawater in the early Holocene, like in the central Bothnian Sea. The subsequent refreshening and reoxygenation, which was caused by gradual isostatic uplift, promoted P burial in the sediment in the form of Mn-rich vivianite. Vivianite authigenesis in the surface sediments of the more isolated part of the estuary ultimately ceased, likely due to continued refreshening and an associated decline in productivity and P supply to the sediment. The observed shifts in environmental conditions also created conditions for post-depositional formation of authigenic vivianite, and possibly apatite formation, at similar to 8 m composite depth. These salinity-related changes in redox conditions and P burial are highly relevant in light of current climate change. The results specifically highlight that increased freshwater input linked to global warming may enhance coastal P retention, thereby contributing to oligotrophication in both coastal and adjacent open waters.