Influence of CO2 and nitrogen limitation on the coccolith volume of Emiliania huxleyi (Haptophyta)

[摘要] Coccolithophores, a key phytoplankton group, are one of the most studiedorganisms regarding their physiological response to oceanacidification/carbonation. The biogenic production of calcareous coccolithshas made coccolithophores a promising group for paleoceanographic researchaiming to reconstruct past environmental conditions. Recently, geochemicaland morphological analyses of fossil coccoliths have gained increasedinterest in regard to changes in seawater carbonate chemistry. Thecosmopolitan coccolithophore Emiliania huxleyi (Lohm.) Hay andMohler was cultured over a range of pCO₂ levels in controlled laboratoryexperiments under nutrient replete and nitrogen limited conditions.Measurements of photosynthesis and calcification revealed, aspreviously published, an increase in particulate organic carbon production and a moderatedecrease in calcification from ambient to elevated pCO₂. The enhancement inparticulate organic carbon production was accompanied by an increase in celldiameter. Changes in coccolith volume were best correlated with thecoccosphere/cell diameter and no significant correlation was found betweenthe coccolith volume and the particulate inorganic carbon production. Theconducted experiments revealed that the coccolith volume of E. huxleyi is variablewith aquatic CO₂ concentration but its sensitivity is rather small incomparison with its sensitivity to nitrogen limitation. Comparing coccolithmorphological and geometrical parameters like volume, mass and size tophysiological parameters under controlled laboratory conditions is animportant step to understand variations in fossil coccolith geometry.

[学科分类] 地球化学与岩石