Pure cultures of the coccolithophoridSyracosphaera carleraewere grown in a synthetic saline medium containing 3.4mM Ca++and 2.0, 1.0, 0.5 or 0.0mM Sr++. The coccoliths were separated by differential centrifugation, washed, dried, and examined by flame photometry and by X-ray diffraction. In the absence of Sr, they consisted of pure calcite. In media containing Sr, the concentration factor or incorporation factor (Sr/Ca in coccoliths Sr/Ca in medium) was approx. 0.02 in each case, indicating a high degree of discrimination against Sr.
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