Carbon dynamics in a productive coastal region—The Skagerrak

Hjalmarsson, Sofia; Chierici, Melissa; Anderson, Leif G.

doi:10.1016/j.jmarsys.2010.05.013

Cited by 3 publications

(2 citation statements)

References 31 publications

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“…Alkalinity is an important component of the carbonate system, and in the southern Baltic Sea it is comparably high (1600-1800 µmol L −1 ), though still considerably lower than in the open ocean (> 2200 µmol L −1 ; Hjalmarsson et al, 2010). The four largest rivers in the Baltic catchment (Neva, Vistula, Daugava, and Odra) all drain through areas with carbonate-rich bedrock as well as carbonate-rich Quaternary deposits.…”

Section: Water Column Differences Between the Kattegat And Hanö Bay (mentioning

confidence: 99%

“…Despite the different species in Hanö Bay this suggests that a relationship between salinity and Mg/Ca should be non-linear. Salinity (and therefore also Mg/Ca sw ) and alkalinity are strongly correlated in seawater; this effect is particularly strong in the Baltic Sea, where the gradients are very large due to fresh water input (Ohlson and Anderson, 1991;Hjalmarsson et al, 2010). Both salinity and carbonate system parameters like alkalinity and the carbonate ion effect are known to have an impact on Mg/Ca in open ocean settings (Elderfield et al, 2006;Raitzsch et al, 2008;Dissard et al, 2010;Huang et al, 2012;Diz et al, 2012).…”

Section: Impact Of Salinity On Mg/ca Forammentioning

confidence: 99%

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

Groeneveld

Filipsson

Austin

et al. 2018

J. Micropalaeontol.

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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 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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Section: Water Column Differences Between the Kattegat And Hanö Bay (mentioning

confidence: 99%

Section: Impact Of Salinity On Mg/ca Forammentioning

confidence: 99%

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

Groeneveld

Filipsson

Austin

et al. 2018

J. Micropalaeontol.

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Mg/Ca and Mn/Ca ratios in benthic foraminifera: the potential to reconstruct past variations in temperature and hypoxia in shelf regions

Groeneveld

Filipsson

2013

Biogeosciences

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Abstract. Shelf and coastal regions are exceptionally important for many countries as they provide the main habitat for many economically important fish and shellfish species. With ongoing climate change and human-induced eutrophication the shelf regions are especially affected, resulting in increased temperatures and stratification as well as oxygen depletion of the bottom waters. In order to be able to predict the magnitude of these changes in the future, it is necessary to study how they varied in the past. Commonly used foraminiferal climate and environmental proxies, e.g., stable isotopes and trace metal/Ca ratios, that are applied in open-ocean settings are not necessarily applicable in shelf regions, either as faunas are significantly different or as conditions can change much faster compared to the open ocean. In this study we explore the use of Mg/Ca as paleothermometer and Mn/Ca as a potential proxy for changing dissolved oxygen conditions in bottom water on the benthic foraminifera Bulimina marginata and Globobulimina turgida. Living specimens were collected from the Skagerrak and the Gullmar Fjord (SW Sweden); the latter is hypoxic for several months a year. As the specimens were alive when collected, we assume it unlikely that any diagenetic coatings have already significantly affected the trace metal/Ca ratios. The Mg/Ca ratios are similar to previously published values but display much larger variation than would be expected from the annual temperature change of less than 2 °C. An additional impact of the difference in the calcite saturation state between the Skagerrak and the Gullmar Fjord could explain the results. Mn/Ca ratios from G. turgida can potentially be related to variations in dissolved oxygen of the habitat where the foraminifera calcify. Samples from the Skagerrak display increased Mn/Ca in specimens that lived deeper in the sediment than those that lived near the surface. G. turgida samples from the low-oxygen Gullmar Fjord showed significantly increased Mn/Ca, being highest when bottom water dissolved oxygen was at a minimum. Our study suggests that trace metal/Ca ratios in benthic foraminifera from shelf regions have the potential to record past variations in bottom water temperature and dissolved oxygen concentrations, but an additional impact of the inorganic carbonate chemistry cannot be excluded.

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Trace metal/Ca ratios in benthic foraminifera: the potential to reconstruct past variations in temperature and hypoxia in shelf regions

Groeneveld¹,

Filipsson²

2013

Preprint

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Shelf and coastal regions are exceptionally important for many countries as they provide the main habitat for many economically important fish and shellfish species. With ongoing global warming and human-induced eutrophication the shelf regions are especially affected, resulting in increased temperatures and stratification as well as oxygen depletion of the bottom waters. In order to be able to predict the magnitude of these changes in the future it is necessary to study how they varied in the past. Commonly used foraminiferal climate and environmental proxies, e.g. stable isotopes and trace metal/Ca ratios, which are applied in open-ocean settings are not necessarily applicable in shelf regions, either as faunas are completely different or as conditions change a-typical compared to the open-ocean. In this study we explore the use of Mg/Ca as paleothermometer and Mn/Ca as a potential proxy for changing dissolved oxygen conditions on the benthic foraminifera Bulimina marginata and Globobulimina turgida. Living specimens were collected from the Skagerrak and the Gullmar Fjord (SW-Sweden); the latter is hypoxic for several months a year. As the specimens were alive when collected it can be excluded that any diagenetic coatings have affected the trace metal/Ca ratios. The Mg/Ca ratios are similar to previously published values from the literature but display much larger variation than would be expected from the annual temperature change of less than 2 °C. An additional impact of the difference in the carbonate ion saturation state between the Skagerrak and the Gullmar Fjord could explain the results. Mn/Ca ratios on Globobulimina turgida potentially record variations in dissolved oxygen of the habitat where the foraminifera calcify. Samples from the Skagerrak display increased Mn/Ca in specimens which lived deeper in the sediment than those that lived near the surface. Globobulimina turgida samples from the lower oxygen Gullmar Fjord showed significantly increased Mn/Ca, being highest when dissolved oxygen was at a minimum. Our study suggests that trace metal/Ca ratios in benthic foraminifera from shelf regions have the potential to record past variations in bottom water temperature and dissolved oxygen concentrations but care needs to be taken to constrain the carbonate system

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Carbon dynamics in a productive coastal region—The Skagerrak

Cited by 3 publications

References 31 publications

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

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

Mg/Ca and Mn/Ca ratios in benthic foraminifera: the potential to reconstruct past variations in temperature and hypoxia in shelf regions

Trace metal/Ca ratios in benthic foraminifera: the potential to reconstruct past variations in temperature and hypoxia in shelf regions

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