Influence of temperature and CO2 on the strontium and magnesium composition of coccolithophore calcite

Müller, Marius N., Lebrato, Mario, Riebesell, Ulf, Barcelos e Ramos, J., Schulz, K. G., Blanco-Ameijeiras, Sonia, Sett, Scarlett, Eisenhauer, Anton and Stoll, H. M. (2014) Influence of temperature and CO2 on the strontium and magnesium composition of coccolithophore calcite Biogeosciences (BG), 11 . pp. 1065-1075. DOI 10.5194/bg-11-1065-2014.

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Abstract

Marine calcareous sediments provide a fundamental basis for paleoceanographic studies aiming to reconstruct past oceanic conditions and understand key biogeochemical element cycles. Calcifying unicellular phytoplankton (coccolithophores) are a major contributor to both carbon and calcium cycling by photosynthesis and the production of calcite (coccoliths) in the euphotic zone and the subsequent long-term deposition and burial into marine sediments. Here we present data from controlled laboratory experiments on four coccolithophore species and elucidate the relation between the divalent cation (Sr, Mg and Ca) partitioning in coccoliths and cellular physiology (growth, calcification and photosynthesis). Coccolithophores were cultured under different seawater temperature and carbonate chemistry conditions. The partition coefficient of strontium (DSr) was positively correlated with both carbon dioxide (pCO2) and temperature but displayed no coherent relation to particulate organic and inorganic carbon production rates. Furthermore, DSr correlated positively with cellular growth rates when driven by temperature but no correlation was present when changes in growth rates were pCO2-induced. The results demonstrate the complex interaction between environmental forcing and physiological control on the strontium partitioning in coccolithophore calcite. The partition coefficient of magnesium (DMg) displayed species-specific differences and elevated values under nutrient limitation. No conclusive correlation between coccolith DMg and temperature was observed but pCO2 induced a rising trend in coccolith DMg. Interestingly, the best correlation was found between coccolith DMg and chlorophyll a production suggesting that chlorophyll a and calcite associated Mg originate from the same intracellular pool. These results give an extended insight into the driving factors that lead to variations in the coccolith Mg / Ca ratio and can be used for Sr / Ca and Mg / Ca paleoproxy calibration.

Document Type: Article
Funder compliance: info:eu-repo/grantAgreement/EC/FP7/211384
Additional Information: WOS:000334100300012
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-BM Biogeochemical Modeling
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-BI Biological Oceanography
Refereed: Yes
DOI etc.: 10.5194/bg-11-1065-2014
ISSN: 1726-4170
Projects: CASIOPEIA, BIOACID, EPOCA
Date Deposited: 25 Feb 2014 08:38
Last Modified: 15 May 2014 07:20
URI: http://oceanrep.geomar.de/id/eprint/23676

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