Henryk Renk, STANISŁAW Ochocki and Mariusz Zalewski
Sea Fisheries Institute, Kołłątaja 1, 81-332 Gdynia, Poland

Key words: assimilation number, photosynthetic light curve, southern Baltic Sea

Abstract.
This paper presents the photosynthetic light curves for phytoplankton of the southern Baltic Sea. The parameters of these curves depend on temperature. The seasonal variations of the parameters of photosynthetic light curves have been described using the following equations:
    The assimilation number  AN = 3.94 - 2.04 * sin(2px + 0.51) + 0.53 * sin(4px + 0.33)
where: x - day, expressed in the form of a decimal fraction of the year. The optimum irradiance for photosynthesis  E_s = 380.7 + 154.8 sin(2px - 1.89) - 39.3 sin(4px - 0.53). Primary production in the gulf and coastal waters may be limited by phosphate deficiency, while in the open sea waters such limitations result from the deficiency of nitrogen compounds.