A Seawater Medium for Dinoflagellates and the Nutrition of Cachonina Niei¹

SUMMARY Two media have been devised: an enriched seawater medium for culture of dinoflagellates and a defined medium for rapid growth of the dinoflagellate Cachonina niei. A wide range in salinity (10.23–42.38 g/liter NaCl) is tolerated by C. niei. Below 0.6 g/liter MgSO 4 , 0.19 g/liter KCl, and 0.22 g/liter CaCl 2 , the generation time greatly increases. Increase in MgSO 4 to 7.22 g/liter, KCl to 1.12 g/liter or CaCl 2 to 2.22 g/liter has little effect on generation time. The temperature optimum is 19–23 C. Saturating light intensity for growth is 1000 ft‐c and for photosynthesis (determined manometrically) is slightly less than 2000 ft‐c. Cachonina niei requires B 12 and thiamin. Neither silicate nor its competitive inhibitor germanate affects generation time or cell yield indicating silicon is not required. Of a variety of buffers tested, Tris is the best. Optimal growth occurs at pHs of 7.5–8.3. Glycerol is inhibitory and does not support dark growth.