Two strains of Phaeocystis sp., one isolated from the Weddell Sea region (Antarctica) and one from the North Sea, were compared for their growth characteristics and pigmentation during growth in batch cultures. Experiments were performed starting with identical nutrient and light conditions at 2°C, 7°C and 10°C. Division rates ranged from 0.17 to 0.94 d-1 depending on strain and temperature: the Antarctic strain grew fastest at 2°C (µ=0.71 d-1), the strain from the North Sea at 10°C (µ=0.94 d-1). Growth phase, phase in the diurnal cycle and temperature influenced the 19'hexanoyloxyfucoxanthin to chlorophyll a ratio in both strains. Large differences in this ratio were found between flagellates and colony cells from the same strain. Despite variability within each strain, mean levels of 19'hexanoyloxyfucoxanthin were always higher in the Antarctic strain. Another fucoxanthin-related pigment, 19'butanoyloxyfucoxanthin, showed the same trends during growth as 19'hexanoyloxyfucoxanthin in the Antarctic strain but was undetectable in the strain isolated from the North Sea. A comparison was made with field data collected during the Phaeocystis blooming period in the coastal zone of the North Sea. During this period relative amounts of 19'hexanoyloxyfucoanthin as well as the absence of 19'butanoyloxyfucoxanthin matched with the results from the North Sea strain in culture. Environmental factors influence pigment content and ratio, yet the two investigated Phaeocystis strains can be distinguished on the basis of their pigment characteristics. |
