Using bath cultures, mathematic methods and phosphorus, the bloom of Emiliania huxleyi (Lohm.) Hay et Mohl. was found for the first time in the northeastern Black Sea shelf. Low-nitrogen phosphorus ratios did not necessarily point nitrogen as a limiting factor for coccolithophorids growth. The reaction of the phytoplankton community to the supply of nitrogen and phosphorus was determined by the composition of dominants species. If in base culture the role of diatoms was dominating, the nitrate and phosphates supply leads to the full domination of these algae due to their higher specific growth rate (maximum growth rate of diatoms was 1.53 day^-1, coccolithophorids – 0.53 day^-1). Nitrogen and phosphorus limitation increased the rate of coccolithophorids cell decay up to 0.20 day^-1.

Keywords: coccolithophorids, phosphorus, limitation, phytoplankton

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