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Holocene Refreshening and Reoxygenation of a Bothnian Sea Estuary Led to Enhanced Phosphorus Burial

Dijkstra, Nikki; Quintana Krupinski, Nadine B. LU ; Yamane, Masako; Obrochta, Stephen P.; Miyairi, Yosuke; Yokoyama, Yusuke and Slomp, Caroline P. (2017) In Estuaries and Coasts
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 δ18O and δ13C 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... (More)

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 δ18O and δ13C 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.

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author
organization
publishing date
type
Contribution to journal
publication status
epub
subject
keywords
Anoxia, Baltic Sea Basin Paleoenvironment, Integrated Ocean Drilling Program, Phosphorus burial, Vivianite, Ångermanälven estuary
in
Estuaries and Coasts
pages
19 pages
publisher
Estuarine Research Federation
external identifiers
  • scopus:85021087056
  • wos:000418591000012
ISSN
1559-2723
DOI
10.1007/s12237-017-0262-x
language
English
LU publication?
yes
id
97c07413-91c4-4ad5-8b75-173362553333
date added to LUP
2017-07-11 14:09:58
date last changed
2018-01-16 13:21:10
@article{97c07413-91c4-4ad5-8b75-173362553333,
  abstract     = {<p>Salinity variations in restricted basins like the Baltic Sea can alter their vulnerability to hypoxia (i.e., bottom water oxygen concentrations &lt;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 δ<sup>18</sup>O and δ<sup>13</sup>C 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.</p>},
  author       = {Dijkstra, Nikki and Quintana Krupinski, Nadine B. and Yamane, Masako and Obrochta, Stephen P. and Miyairi, Yosuke and Yokoyama, Yusuke and Slomp, Caroline P.},
  issn         = {1559-2723},
  keyword      = {Anoxia,Baltic Sea Basin Paleoenvironment,Integrated Ocean Drilling Program,Phosphorus burial,Vivianite,Ångermanälven estuary},
  language     = {eng},
  month        = {06},
  pages        = {19},
  publisher    = {Estuarine Research Federation},
  series       = {Estuaries and Coasts},
  title        = {Holocene Refreshening and Reoxygenation of a Bothnian Sea Estuary Led to Enhanced Phosphorus Burial},
  url          = {http://dx.doi.org/10.1007/s12237-017-0262-x},
  year         = {2017},
}