Testing the Influence of Changing Seawater Ca Concentration on Elements/Ca Ratios in Planktic Foraminifera: A Culture Experiment
Abstract Element/Ca ratios in foraminifera shells are used to assess oceanic physical‐chemical properties (e.g., paleo‐temperature, paleo‐pH…). On geological time scales, these proxies may also depend on changes in the chemical composition of seawater. Here we investigate the effect of changing seaw...
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| Format: | Article |
| Language: | English |
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Wiley
2021-03-01
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| Series: | Geochemistry, Geophysics, Geosystems |
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| Online Access: | https://doi.org/10.1029/2020GC009496 |
| _version_ | 1797638026355015680 |
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| author | Sandrine Le Houedec Jonathan Erez Yair Rosenthal |
| author_facet | Sandrine Le Houedec Jonathan Erez Yair Rosenthal |
| author_sort | Sandrine Le Houedec |
| collection | DOAJ |
| description | Abstract Element/Ca ratios in foraminifera shells are used to assess oceanic physical‐chemical properties (e.g., paleo‐temperature, paleo‐pH…). On geological time scales, these proxies may also depend on changes in the chemical composition of seawater. Here we investigate the effect of changing seawater calcium concentration on the Li/Ca, Mg/Ca, Sr/Ca, B/Ca, and Na/Ca ratios in low‐Mg calcite shells of the planktic foraminifer Globigerinella siphonifera. Specifically, we evaluate the possibility that Na/Ca in planktic foraminifera shells may serve as a proxy for Ca concentrations in the past ocean. Since Ca concentration in today's open ocean is largely conservative with relation to salinity, field calibrations are not possible. Therefore, we cultured the planktic foraminifer (G. siphonifera) collected from the Gulf of Eilat (Red Sea) in variable Casw (10.5–29 mmol/kg), at constant temperature (25°C) and under two salinities (37 and 40.6). When changing the Casw of the growth medium, the relationships between Mg/Ca and Na/Ca in the shells and their corresponding ratios in the seawater are best described by power functions implying a variable distribution coefficient function. For Sr/Ca and Li/Ca, the relations between the shells and the seawater are described by linear functions intersecting the origin implying their distribution coefficients are insensitive to changes in Casw. The results also confirm that foraminiferal B/Ca is not influenced by seawater Casw. We conclude that Na/Ca ratios in planktic foraminifera may serve as reliable proxy for Cenozoic ocean Ca, and that other El/Ca ratios may be used to determine their past concentrations relative to Ca. |
| first_indexed | 2024-03-11T12:57:46Z |
| format | Article |
| id | doaj.art-a6bc1099e25d40c89e43b1a6be8c3984 |
| institution | Directory Open Access Journal |
| issn | 1525-2027 |
| language | English |
| last_indexed | 2024-03-11T12:57:46Z |
| publishDate | 2021-03-01 |
| publisher | Wiley |
| record_format | Article |
| series | Geochemistry, Geophysics, Geosystems |
| spelling | doaj.art-a6bc1099e25d40c89e43b1a6be8c39842023-11-03T17:00:24ZengWileyGeochemistry, Geophysics, Geosystems1525-20272021-03-01223n/an/a10.1029/2020GC009496Testing the Influence of Changing Seawater Ca Concentration on Elements/Ca Ratios in Planktic Foraminifera: A Culture ExperimentSandrine Le Houedec0Jonathan Erez1Yair Rosenthal2Institute of Earth Sciences The Hebrew University of Jerusalem Jerusalem IsraelInstitute of Earth Sciences The Hebrew University of Jerusalem Jerusalem IsraelInstitute for Marine and Coastal Sciences and Department of Earth and Planetary Sciences Rutgers University New Brunswick NJ USAAbstract Element/Ca ratios in foraminifera shells are used to assess oceanic physical‐chemical properties (e.g., paleo‐temperature, paleo‐pH…). On geological time scales, these proxies may also depend on changes in the chemical composition of seawater. Here we investigate the effect of changing seawater calcium concentration on the Li/Ca, Mg/Ca, Sr/Ca, B/Ca, and Na/Ca ratios in low‐Mg calcite shells of the planktic foraminifer Globigerinella siphonifera. Specifically, we evaluate the possibility that Na/Ca in planktic foraminifera shells may serve as a proxy for Ca concentrations in the past ocean. Since Ca concentration in today's open ocean is largely conservative with relation to salinity, field calibrations are not possible. Therefore, we cultured the planktic foraminifer (G. siphonifera) collected from the Gulf of Eilat (Red Sea) in variable Casw (10.5–29 mmol/kg), at constant temperature (25°C) and under two salinities (37 and 40.6). When changing the Casw of the growth medium, the relationships between Mg/Ca and Na/Ca in the shells and their corresponding ratios in the seawater are best described by power functions implying a variable distribution coefficient function. For Sr/Ca and Li/Ca, the relations between the shells and the seawater are described by linear functions intersecting the origin implying their distribution coefficients are insensitive to changes in Casw. The results also confirm that foraminiferal B/Ca is not influenced by seawater Casw. We conclude that Na/Ca ratios in planktic foraminifera may serve as reliable proxy for Cenozoic ocean Ca, and that other El/Ca ratios may be used to determine their past concentrations relative to Ca.https://doi.org/10.1029/2020GC009496calcium concentrationcultureforaminiferatrace element |
| spellingShingle | Sandrine Le Houedec Jonathan Erez Yair Rosenthal Testing the Influence of Changing Seawater Ca Concentration on Elements/Ca Ratios in Planktic Foraminifera: A Culture Experiment Geochemistry, Geophysics, Geosystems calcium concentration culture foraminifera trace element |
| title | Testing the Influence of Changing Seawater Ca Concentration on Elements/Ca Ratios in Planktic Foraminifera: A Culture Experiment |
| title_full | Testing the Influence of Changing Seawater Ca Concentration on Elements/Ca Ratios in Planktic Foraminifera: A Culture Experiment |
| title_fullStr | Testing the Influence of Changing Seawater Ca Concentration on Elements/Ca Ratios in Planktic Foraminifera: A Culture Experiment |
| title_full_unstemmed | Testing the Influence of Changing Seawater Ca Concentration on Elements/Ca Ratios in Planktic Foraminifera: A Culture Experiment |
| title_short | Testing the Influence of Changing Seawater Ca Concentration on Elements/Ca Ratios in Planktic Foraminifera: A Culture Experiment |
| title_sort | testing the influence of changing seawater ca concentration on elements ca ratios in planktic foraminifera a culture experiment |
| topic | calcium concentration culture foraminifera trace element |
| url | https://doi.org/10.1029/2020GC009496 |
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