Abstract
Suitable culture medium for the rapid growth of a coccolithophorid, Emiliania huxleyi, was found to be either natural or artificial seawater enriched with Erd-Schreiber's medium (ESM) and Keller's medium (K). Guillard's f/2 medium and PES (Provasoli's enriched seawater) were less effective. When ESM without soil extracts was added as an enrichment, algal growth was partly suppressed in the artificial seawater of Jamarin S, Sea Life and Marine Art SF, in this sequence. The suppression of growth by the removal of soil extracts was also checked by the addition of selenium. These results suggest that selenium is essential to the growth of Emiliania huxleyi and soil extracts in the ESM enrichment can be replaced with selenium. Both selenium dioxide and sodium selenite were more effective on growth than was sodium selenate below 0.1 mM-level. The optimum concentrations were 1-10 nM for SeO2and SeO2-3 and above 1 μM for SeO2-4. In contrast to the growth, the rate of photosynthetic 14CO2 fixation in Emiliania huxleyi was not affected by the depletion of selenium, indicating that the suppression of growth may not be due to the inhibition of photosynthesis.
