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Validation of seasonal proxies using planktic foraminifera
Project leader: Dr. G. J. Reichart
Researcher(s): Dr. L.J. de Nooijer
Starting date: 01-04-2010

Abstract
Foraminifera provide information on seawater properties in the chemical and isotopic composition of their tests. Those species calcifying throughout the year hold the potential to reflect the full seasonal range in seawater parameters and can thus be used accordingly in in paleoceanographic reconstructions. In order to establish the impact of seasonality on the chemistry of precipitiated calcite, foraminiferal tests will be analyzed which are collected throughout the year. This yields a calibration dataset reflecting all (including extreme) values, rather than yearly averages. Temperature values will be determined by the simultaneous analyses of Mg/Ca ratios and δ18O of single planktic specimens. Here we propose to develop foraminifera-based proxies that will increase the resolution of such reconstructions to the seasonal scale. Since planktic foraminifera have a short lifespan, the calcite they produce reflects the environment of the same short interval. Coupled analysis of Mg/Ca and δ18O of single specimens from material collected year-round at two sites in the Arabian Sea and will allow us to precisely calibrate the relation between seasonality and calcite chemistry. In addition, available material from plankton tows from the same areas will allow us to constrain the coupled effects of temperature, salinity and upwelling on the geochemical proxies.

Publications
Raitzsch M, Duenas-Bohorquez A, Reichart GJ, De Nooijer LJ, Bickert T (2010). Incorporation of Mg and Sr in calcite of cultured benthic foraminifera: impact of calcium concentration and associated calcite saturation state. BIOGEOSCIENCES7: 869-881.
Darwin Center authors: de Nooijer L.J., Reichart G. J.

Langer G, De Nooijer LJ, Oetjen K (2010). On the role of the cytoskeleton in coccolith morphogenesis: The effect of cytoskeleton inhibitors. PHYCOLOGY46: 1252-1256.
Darwin Center authors: Langer G., de Nooijer L.J.

Duenas-Bohorquez A, da Rocha RE, Kuroyanagi A, De Nooijer LJ, Bijma J, Reichart GJ (2011). Interindividual variability and ontogenetic effects on Mg and Sr incorporation in the planktonic foraminifer Globigerinoides sacculifer. GEOCHIMICA ET COSMOCHIMICA ACTA75: 520-532.
Darwin Center authors: Bijma J., de Nooijer L.J., Reichart G. J.