Krug, Sebastian (2006) Impact of CO2-induced seawater acidificationon on the calcification of Coccolithus pelagicus. (Diploma thesis), Christian-Albrechts-Universität zu Kiel, Kiel, Germany, 41 pp.

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Abstract

This study presents new insights on variations in the coccolithophore Coccolithus pelagicus due to a rising C02 concentration, caused by anthropogenic emissions. Since coccolithophores are the dominant group of pelagic calicifiers, variations in calcification and photosynthesis will have direct consequences for the global carbon cycle and hence atmospheric CO2. The research was conducted as a batch culture experiment in which C. pelagicus was grown under light and nutrient replete conditions at five different CO2 concentrations (10, 20, 30, 40 and 50μmol/kg). In previous experiments with the coccolithophores Emiliania huxleyi and Gephyrocapsa oceanica acidification due to the rising CO2 concentrations could show no effect on the growth rate, but calcification was significantly reduced while photosynthesis was promoted. This study could show same effects. There is no trend in growth rates and the transport efficiency of photosystem II (Fv/Fm) was not affected by CO2 concentrations up to 40 μmol/kg. However, at higher CO2 concentrations the efficiency decreased. Nevertheless, this reduction seems not to have influenced photosynthesis nor growth rates. The production of organic carbon significantly increased from the lowest to the highest C02 concentration, what leads to a rise of the organic carbon content by 50%. This is probably caused by a decrease in the passive loss of CO2 and an increase in the transport capacity of CO2 and HCO3-. The inorganic carbon on the other hand significantly decreased with rising CO2. There are not yet any explanations or presumptions for a reason but it is certified by studies on other coccolithophores. Finally, it can be stated that that a decrease in calcification and an increase in photosynthesis in Coccolithus pelagicus could have a negative feedback on the future atmospheric CO2. However, this potential negative feedback by C. pelagicus would not be as pronounced as it can be assumed for E. huxleyi and G. oceanica.

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