8th International Nannoplankton Association Conference


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Heather Stoll, Christine Klaas, Ian Probert, Patrizia Ziveri, Jorge R. Encinar, Ignacio G. Alonso:
Sr/Ca of coccolith carbonate: testing the stories of the smallest carbonate repositories

Field studies in the equatorial Pacific have suggested that the Sr/Ca ratio of coccolith calcite might depend on the growth and calcification rate of coccolithophorids. In the context of CODENET, we have been able to undertake a multifaceted approach to evaluate the utility of coccolith elemental chemistry for palaeoceagraphic and palaeoclimatological studies. Culture experiments with several species of coccolithophorids show upto 40% variation in Sr partitioning in coccolith calcite, in response to changing coccolithophorid growth and calcification rates, and varying culture temperatures and alkalinities. Culture experiments also indicate different Sr partitioning by different species cultured under similar conditions. In sediments, a range of Sr partitioning is also observed in fractions enriched in different species. Core-top sediments in the Somali upwelling region show a direct relationship between Sr/Ca of the coccolith fraction and upwelling intensity. Work to measure Mg/Ca ratios in culture samples, likely to reflect culture temperature, is currently underway. This combined approach permits a realistic assessment of the potential for using coccolith Sr/Ca to infer past changes in coccolithophorid productivity, to infer past changes in the organic/inorganic carbon rain ratio, and to correct alkenone pCO2 estimates for variations in coccolithophorid growth rates.


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 [Division of Micropalaeontology] [Department of Geosciences] [Bremen University]

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