CELL AND GROWTH-CHARACTERISTICS OF TYPE-A AND TYPE-B OF EMILIANIA-HUXLEYI (PRYMNESIOPHYCEAE) AS DETERMINED BY FLOW-CYTOMETRY AND CHEMICAL-ANALYSES

Two morphotypes of Emiliania huxleyi (Lohmann 1902) Hay et al. 1967, t ypes A and B, known to be unequally distributed in the oceans, were gr own in dilution cultures at a range of photon flux densities (PFDs) (1 .5-155 mumol photons.m-2.s-1) and two temperatures (10-degrees and 15- degrees-C). Calcite carbon and organic carbon content of the cells as well as instantaneous growth rate, cell size, chlorophyll fluorescence , and light-scatter properties clearly depended on growth conditions a nd differed considerably for the two morphotypes. The ratio between ca lcite carbon and organic carbon production showed an optimum of 0.65 i n E. huxleyi type A cells at PFD = 17.5. The ratio increased slightly with a temperature increase from 10-degrees to 15-degrees-C but remain ed < 1.0 at both temperatures in light-limited cells. In contrast, cal cite carbon production exceeded organic carbon production (ratio: 1.4- 2.2) in phosphate-deprived cultures. Emiliania huxleyi type B generall y showed a higher calcite carbon/organic carbon ratio than E. huxleyi type A, but the relation with PFD was similar. The content Of calcite carbon and organic carbon as well as the instantaneous growth rate, ce ll size, chlorophyll fluorescence, and light-scatter properties showed large diel variations that were closely related to the division cycle . Our results show the importance of mapping the structure of any samp led cell population with respect to the phase in the cell division cyc le, as this largely determines the outcome of not only ''per cell'' me asurements but also short time (less than 24 h)flux measurements. For instance, dark production of calcite by E. huxleyi was negatively affe cted by cell division. Slowly growing (phosphate-stressed) cultures pr oduced calcite in the light and in the dark. In contrast, rapidly grow ing cultures at 10-degrees-C produced calcite only in the light, where as in the dark there was a significant loss of calcite due to dissolut ion.