ENHANCED CALCIFICATION IN THE COCCOLITHOPHORID EMILIANIA-HUXLEYI (HAPTOPHYCEAE) UNDER PHOSPHORUS LIMITATION

The effect of phosphorus limitation on calcification in the coccolitho phorid Emiliania huxleyi (Lohmann) Hay et Mohler was investigated by c hemical Ca and C analyses, as well as in short-term C-14 uptake experi ments. The latter made use of a newly developed microdiffusion method to separate C-14 in coccolith carbonate from photosynthetically assimi lated C-14. In comparison with exponentially growing cells in a nutrie nt-replete medium, cells grown in P-limited chemostats at half the max imum growth rate produced c. 60% more CaCO3 relative to organic carbon . In the short-term incubations, cells from P-limited chemostats showe d a relative increase in the capacity for calcification under reduced irradiance and in the dark. Nutrient effects on calcification are of p otential interest in considerations of the impact of E. huxleyi blooms on the sea-air CO2 interchange, and they deserve further study.