LIGHT-DEPENDENT COCCOLITH FORMATION IN 2 FORMS OF COCCOLITHUS PELAGICUS - WITH REMARKS ON 14C ZERO-THICKNESS COUNTING EFFICIENCY OF COCOLITHOPHORIDS

Two methods were employed for measuring coccolith formation and photosynthesis in coccolithophorids. The first method was based on measurements of 14C radioactivity of cells on membrane filters before and after acid treatment. The second method involved a conversion of 14C in coccoliths or whole cells to BaCO3 prior to counting. It was observed that in determinations of photosynthetic (or total) 14C by the first method, the count rate produced by a given amount of the isotope was 30-40% lower in the non-motile and motile forms of Coccolithus pelagicus than in C. huxleyi. There was no similarly great discrepancy in determinations of coccolith 14C. Light-dependent coccolith formation was demonstrated in both forms of C. pelagicus. The non-motile form may deposit several times more carbon in its coccoliths than it assimilates photosynthetically. In the motile form, coccolith carbon amounts to less than 2% of photosynthetic carbon. © 1969 Springer-Verlag.