CALCIFICATION, PHOTOSYNTHESIS AND GROWTH OF THE BLOOM-FORMING COCCOLITHOPHORE, EMILIANIA-HUXLEYI

Measurements were made of photosynthesis and calcification in a bloom of coccolithophores in the Gulf of Maine as well as in laboratory batch cultures of the Emiliania huxleyi strain 88E. The C-14 technique for measuring calcification was evaluated with calcifying and non-calcifying coccolithophore strains. Shipboard bloom observations showed physiological evidence of stratification between surface and deep populations within the surface mixed layer. Photosynthesis and calcification rates were enhanced within hours of addition of KNO3 or nitrate-rich deep water (to the same final concentration). Such rates were strongly temperature dependent in laboratory cultures, decreasing over a factor of two from 15 to 20-degrees-C. Calcification was considerably less light-dependent than photosynthesis and consistently had a measurable dark rate. In culture, maximum calcification rates and degree of cell plating were limited to logarithmic growth phase. This was followed by rapid increase in the coccolith shedding rate 1 day prior to the onset of stationary phase which continued several days after cell division stopped. The regional significance of these features to total organic and inorganic carbon production as well as calcite burial is discussed.