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NUTRIENT REQUIREMENTS OF THE DINOFLAGELLATE PERIDINIUM GATUNENSE 1

Optimum nutrient conditions for growth and photosynthesis of Peridinium gatunense (Nygaard) (Peridinium cinctum fa. westii) were investigated using axenic clones in batch cultures. Selenium (Se) had previously been found to be an indispensable growth factor for P. gatunense. Optimal, suboptimal, and supraoptimal concentrations of HCO3−, N, Ca, Cl, Mg, P, K, S, Si, EDTA‐Na, Fe, Mo, Zn, Mn, Co, Se, B, Br, I, and various trace element mixtures were determined by measuring biomass development, growth rates, 14C uptake, and/or oxygen production at various concentration gradients of these elements. The general characteristics of the best formulation, medium‐L 16, relative to other media, are its high content of NaHCO3 (1 meq · L−1) and Mo (0.2 μM) but low concentrations of NO3‐N (150 μM), PO4‐P (10 μM), and Fe (0.4 μM), in addition to its content of Se. The total content of trace metals, except for Se, may be reduced to one‐fourth of that in medium‐L 16 without altering the major growth‐promoting properties of the medium. Medium‐L 16 deviated considerably from Lake Kinneret (Israel) water, being much lower in macroelements except for N and P. The pH (8.1–8.4) was in the same range, but the values of conductivity (140 μS · cm−1), alkalinity (1 meq · L−1) and NaCl (200 μM) were > 8, 2, and 30 times higher, respectively, in the lake water. Selenium deficiency may limit the growth of P. gatunense in this lake.