Holocene Refreshening and Reoxygenation of a Bothnian Sea Estuary Led to Enhanced Phosphorus BurialReport as inadecuate




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Estuaries and Coasts

pp 1–19

First Online: 21 June 2017Received: 23 September 2016Revised: 28 March 2017Accepted: 28 April 2017DOI: 10.1007-s12237-017-0262-x

Cite this article as: Dijkstra, N., Quintana Krupinski, N.B., Yamane, M. et al. Estuaries and Coasts 2017. doi:10.1007-s12237-017-0262-x

Abstract

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 δO and δC analyses to reconstruct the bottom water salinity, redox conditions, and P burial in the Ångermanälven 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 Ångermanälven 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 ∼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.

KeywordsIntegrated Ocean Drilling Program Baltic Sea Basin Paleoenvironment Ångermanälven estuary Phosphorus burial Vivianite Anoxia Communicated by David Reide Corbett

Electronic supplementary materialThe online version of this article doi:10.1007-s12237-017-0262-x contains supplementary material, which is available to authorized users.





Author: Nikki Dijkstra - Nadine B. Quintana Krupinski - Masako Yamane - Stephen P. Obrochta - Yosuke Miyairi - Yusuke Yokoyama - C

Source: https://link.springer.com/







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