Response of the dinoflagellate Alexandrium tamarense to a range of nitrogen sources and concentrations: growth rate, chemical carbon and nitrogen, and pigments

The responses of cellular C and N, pigments and growth rates of Alexandrium tamarense to different sources of N at high concentrations (6, 12, 25, 50 and 100 μM-N) were examined. Nitrate induced the highest concentration of cellular C (an indicator of biovolume) and cellular N, followed by ammonium and then urea. Cellular C to N ratio (an indicator of physiological status) also varied between N sources. Nitrate grown cells had lower range of C:N ratios and ammonium grown cells had highly variable range. Urea cultures had the highest range of cellular C:N ratio. Pigment composition remained unchanged with all N substrates. The pigments decreased with increasing nitrate concentrations, but with ammonium pigments increased. On the other hand, urea concentrations had no clear relationship with cellular pigments. Variability in the growth of cells was due to both the physiological condition and pigments. When the cells are exposed to different N environments and concentration, they exhibit a physiological acclimation by regulating their cellular materials which is associated with growth.