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Assessing proxy signatures of temperature, salinity, and hypoxia in the Baltic Sea through foraminifera-based geochemistry and faunal assemblages

Groeneveld, Jeroen LU ; Filipsson, Helena L. LU ; Austin, William E.N. ; Darling, Kate ; McCarthy, David ; Krupinski, Nadine B.Quintana LU ; Bird, Clare and Schweizer, Magali (2018) In Journal of Micropalaeontology 37(2). p.403-429
Abstract

Current climate and environmental changes strongly affect shallow marine and coastal areas like the Baltic Sea. This has created a need for a context to understand the severity and potential outcomes of such changes. The context can be derived from paleoenvironmental records during periods when comparable events happened in the past. In this study, we explore how varying bottom water conditions across a large hydrographic gradient in the Baltic Sea affect benthic foraminiferal faunal assemblages and the geochemical composition of their calcite tests. We have conducted both morphological and molecular analyses of the faunas and we evaluate how the chemical signatures of the bottom waters are recorded in the tests of several species of... (More)

Current climate and environmental changes strongly affect shallow marine and coastal areas like the Baltic Sea. This has created a need for a context to understand the severity and potential outcomes of such changes. The context can be derived from paleoenvironmental records during periods when comparable events happened in the past. In this study, we explore how varying bottom water conditions across a large hydrographic gradient in the Baltic Sea affect benthic foraminiferal faunal assemblages and the geochemical composition of their calcite tests. We have conducted both morphological and molecular analyses of the faunas and we evaluate how the chemical signatures of the bottom waters are recorded in the tests of several species of benthic foraminifera. We focus on two locations, one in the Kattegat (western Baltic Sea) and one in Hanö Bay (southern Baltic Sea). We show that seawater Mn-•Ca, Mg-•Ca, and Ba-•Ca (Mn-•Casw, Mg-•Casw, and Ba-•Casw) variations are mainly controlled by dissolved oxygen concentration and salinity. Their respective imprints on the foraminiferal calcite demonstrate the potential of Mn-•Ca as a proxy for hypoxic conditions, and Ba-•Ca as a proxy for salinity in enclosed basins such as the Baltic Sea. The traditional use of Mg-•Ca as a proxy to reconstruct past seawater temperatures is not recommended in the region, as it may be overprinted by the large variations in salinity (specifically on Bulimina marginata), Mg-•Casw, and possibly also the carbonate system. Salinity is the main factor controlling the faunal assemblages: a much more diverse fauna occurs in the higher-salinity (- 32) Kattegat than in the low-salinity (- 15) Hanö Bay. Molecular identification shows that only Elphidium clavatum occurs at both locations, but other genetic types of both genera Elphidium and Ammonia are restricted to either low- or high-salinity locations. The combination of foraminiferal geochemistry and environmental parameters demonstrates that in a highly variable setting like the Baltic Sea, it is possible to separate different environmental impacts on the foraminiferal assemblages and therefore use Mn-•Ca, Mg-•Ca, and Ba-•Ca to reconstruct how specific conditions may have varied in the past.

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author
; ; ; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of Micropalaeontology
volume
37
issue
2
pages
27 pages
publisher
Geological Society of London
external identifiers
  • scopus:85053426508
ISSN
0262-821X
DOI
10.5194/jm-37-403-2018
project
Fält och experimentell kalibrering av marina temperaturindikatorer genom användning av bentiska foraminiferer
language
English
LU publication?
yes
id
7a3fdc63-83a8-4515-8c68-bb86e91fc72b
date added to LUP
2018-10-12 07:55:04
date last changed
2020-10-07 06:04:50
@article{7a3fdc63-83a8-4515-8c68-bb86e91fc72b,
  abstract     = {<p>Current climate and environmental changes strongly affect shallow marine and coastal areas like the Baltic Sea. This has created a need for a context to understand the severity and potential outcomes of such changes. The context can be derived from paleoenvironmental records during periods when comparable events happened in the past. In this study, we explore how varying bottom water conditions across a large hydrographic gradient in the Baltic Sea affect benthic foraminiferal faunal assemblages and the geochemical composition of their calcite tests. We have conducted both morphological and molecular analyses of the faunas and we evaluate how the chemical signatures of the bottom waters are recorded in the tests of several species of benthic foraminifera. We focus on two locations, one in the Kattegat (western Baltic Sea) and one in Hanö Bay (southern Baltic Sea). We show that seawater Mn-•Ca, Mg-•Ca, and Ba-•Ca (Mn-•Ca<sub>sw</sub>, Mg-•Ca<sub>sw</sub>, and Ba-•Ca<sub>sw</sub>) variations are mainly controlled by dissolved oxygen concentration and salinity. Their respective imprints on the foraminiferal calcite demonstrate the potential of Mn-•Ca as a proxy for hypoxic conditions, and Ba-•Ca as a proxy for salinity in enclosed basins such as the Baltic Sea. The traditional use of Mg-•Ca as a proxy to reconstruct past seawater temperatures is not recommended in the region, as it may be overprinted by the large variations in salinity (specifically on <i>Bulimina marginata</i>), Mg-•Ca<sub>sw</sub>, and possibly also the carbonate system. Salinity is the main factor controlling the faunal assemblages: a much more diverse fauna occurs in the higher-salinity (- 32) Kattegat than in the low-salinity (- 15) Hanö Bay. Molecular identification shows that only <i>Elphidium clavatum</i> occurs at both locations, but other genetic types of both genera <i>Elphidium</i> and <i>Ammonia</i> are restricted to either low- or high-salinity locations. The combination of foraminiferal geochemistry and environmental parameters demonstrates that in a highly variable setting like the Baltic Sea, it is possible to separate different environmental impacts on the foraminiferal assemblages and therefore use Mn-•Ca, Mg-•Ca, and Ba-•Ca to reconstruct how specific conditions may have varied in the past.</p>},
  author       = {Groeneveld, Jeroen and Filipsson, Helena L. and Austin, William E.N. and Darling, Kate and McCarthy, David and Krupinski, Nadine B.Quintana and Bird, Clare and Schweizer, Magali},
  issn         = {0262-821X},
  language     = {eng},
  month        = {09},
  number       = {2},
  pages        = {403--429},
  publisher    = {Geological Society of London},
  series       = {Journal of Micropalaeontology},
  title        = {Assessing proxy signatures of temperature, salinity, and hypoxia in the Baltic Sea through foraminifera-based geochemistry and faunal assemblages},
  url          = {http://dx.doi.org/10.5194/jm-37-403-2018},
  doi          = {10.5194/jm-37-403-2018},
  volume       = {37},
  year         = {2018},
}