Rapid environmental responses to climate-induced hydrographic changes in the Baltic Sea entrance
<p>The Öresund (the Sound), which is a part of the Danish straits, is linking the marine North Sea and the brackish Baltic Sea. It is a transition zone where ecosystems are subjected to large gradients in terms of salinity, temperature, carbonate chemistry, and dissolved oxygen concentration....
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doaj-bb3f22bb498047098881c25b6edf4ce12020-11-24T21:44:15ZengCopernicus PublicationsBiogeosciences1726-41701726-41892019-10-01163835385210.5194/bg-16-3835-2019Rapid environmental responses to climate-induced hydrographic changes in the Baltic Sea entranceL. M. Charrieau0K. Ljung1F. Schenk2U. Daewel3E. Kritzberg4H. L. Filipsson5Department of Geology, Lund University, Lund, SwedenDepartment of Geology, Lund University, Lund, SwedenBolin Centre for Climate Research and Department of Geological Sciences, Stockholm University, Stockholm, SwedenDepartment of System Analysis and Modelling, Centre for Materials and Coastal Research, Geesthacht, GermanyDepartment of Biology, Lund University, Lund, SwedenDepartment of Geology, Lund University, Lund, Sweden<p>The Öresund (the Sound), which is a part of the Danish straits, is linking the marine North Sea and the brackish Baltic Sea. It is a transition zone where ecosystems are subjected to large gradients in terms of salinity, temperature, carbonate chemistry, and dissolved oxygen concentration. In addition to the highly variable environmental conditions, the area is responding to anthropogenic disturbances in, e.g., nutrient loading, temperature, and pH. We have reconstructed environmental changes in the Öresund during the last ca. 200 years, and especially dissolved oxygen concentration, salinity, organic matter content, and pollution levels, using benthic foraminifera and sediment geochemistry. Five zones with characteristic foraminiferal assemblages were identified, each reflecting the environmental conditions for the respective period. The largest changes occurred around 1950, when the foraminiferal assemblage shifted from a low diversity fauna dominated by the species <i>Stainforthia fusiformis</i> to higher diversity and abundance and dominance of the <i>Elphidium</i> species. Concurrently, the grain-size distribution shifted from clayey to sandier sediment. To explore the causes of the environmental changes, we used time series of reconstructed wind conditions coupled with large-scale climate variations as recorded by the North Atlantic Oscillation (NAO) index as well as the ECOSMO II model of currents in the Öresund area. The results indicate increased changes in the water circulation towards stronger currents in the area after the 1950s. The foraminiferal fauna responded quickly (<10 years) to the environmental changes. Notably, when the wind conditions, and thereby the current system, returned in the 1980s to the previous pattern, the foraminiferal assemblage did not rebound. Instead, the foraminiferal faunas displayed a new equilibrium state.</p>https://www.biogeosciences.net/16/3835/2019/bg-16-3835-2019.pdf |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
L. M. Charrieau K. Ljung F. Schenk U. Daewel E. Kritzberg H. L. Filipsson |
spellingShingle |
L. M. Charrieau K. Ljung F. Schenk U. Daewel E. Kritzberg H. L. Filipsson Rapid environmental responses to climate-induced hydrographic changes in the Baltic Sea entrance Biogeosciences |
author_facet |
L. M. Charrieau K. Ljung F. Schenk U. Daewel E. Kritzberg H. L. Filipsson |
author_sort |
L. M. Charrieau |
title |
Rapid environmental responses to climate-induced hydrographic changes in the Baltic Sea entrance |
title_short |
Rapid environmental responses to climate-induced hydrographic changes in the Baltic Sea entrance |
title_full |
Rapid environmental responses to climate-induced hydrographic changes in the Baltic Sea entrance |
title_fullStr |
Rapid environmental responses to climate-induced hydrographic changes in the Baltic Sea entrance |
title_full_unstemmed |
Rapid environmental responses to climate-induced hydrographic changes in the Baltic Sea entrance |
title_sort |
rapid environmental responses to climate-induced hydrographic changes in the baltic sea entrance |
publisher |
Copernicus Publications |
series |
Biogeosciences |
issn |
1726-4170 1726-4189 |
publishDate |
2019-10-01 |
description |
<p>The Öresund (the Sound), which is a part of the Danish straits, is
linking the marine North Sea and the brackish Baltic Sea. It is a transition
zone where ecosystems are subjected to large gradients in terms of salinity,
temperature, carbonate chemistry, and dissolved oxygen concentration. In
addition to the highly variable environmental conditions, the area is
responding to anthropogenic disturbances in, e.g., nutrient loading,
temperature, and pH. We have reconstructed environmental changes in the
Öresund during the last ca. 200 years, and especially dissolved oxygen
concentration, salinity, organic matter content, and pollution levels, using
benthic foraminifera and sediment geochemistry. Five zones with
characteristic foraminiferal assemblages were identified, each reflecting
the environmental conditions for the respective period. The largest changes
occurred around 1950, when the foraminiferal assemblage shifted from a low
diversity fauna dominated by the species <i>Stainforthia fusiformis</i> to higher diversity and
abundance and dominance of the <i>Elphidium</i> species. Concurrently, the grain-size
distribution shifted from clayey to sandier sediment. To explore the
causes of the environmental changes, we used time series of reconstructed
wind conditions coupled with large-scale climate variations as recorded by
the North Atlantic Oscillation (NAO) index as well as the ECOSMO II model
of currents in the Öresund area. The results indicate increased changes
in the water circulation towards stronger currents in the area after the
1950s. The foraminiferal fauna responded quickly (<10 years) to
the environmental changes. Notably, when the wind conditions, and thereby
the current system, returned in the 1980s to the previous pattern, the
foraminiferal assemblage did not rebound. Instead, the foraminiferal faunas
displayed a new equilibrium state.</p> |
url |
https://www.biogeosciences.net/16/3835/2019/bg-16-3835-2019.pdf |
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