COCCOLITH PRODUCTION AND DETACHMENT BY EMILIANIA HUXLEYI (PRYMNESIOPHYCEAE)1

Abstract

ABSTRACTLaboratory experiments were performed with the prymnesiophyte Emiliania huxleyi (Lohm.) Hay and Mohler, strain 88E, to quantify calcification per cell, coccolith detachment, and effects of coccolith production on optical scattering of individual cells. 14C incorporation into attached and detached coccoliths was measured using a bulk filtration technique. 14C‐labeled cells also were sorted using a flow cytometer and analyzed for carbon incorporation into attached coccoliths. The difference between the bulk and flow cytometer analyses provided a 14C‐based estimate of the rate of production of detached coccoliths. Coccolith production and detachment were separated in time in batch cultures, with most detachment happening well after calcification had stopped. Accumulation of coccoliths was maximum at the end of logarithmic growth with 50–80 coccoliths per cell (three to five complete layers of coccoliths around the cells). Net accretion rates of coccoliths were on the order of 7 coccoliths· cell−1·d−1 while net detachment rates were as high as 15 coccoliths· cell−1·d−1 for stationary phase cells. Equal numbers of coccoliths were attached and detached early in logarithmic growth, and as cells aged, the numbers of detached coccoliths exceeded the attached ones by a factor of 6. Our results demonstrate pronounced charges of forward angle light scatter and 90° light scatter of cells as they grow logarithmically and enter stationary phase. Counts of loose coccoliths in batch cultures are consistent with the detachment of coccoliths in layers rather than individual coccoliths.