Dependence of Sub-Cellular Activities of the Blooming and Harmful Dinoflagellate Cochlodinium Polykrikoides on Temperature

Water temperature-dependent fluctuations of biochemical and molecular activities in the harmful dinoflagellate, Cochlodinium polykrikoides were studied. In terms of genomic DNA concentration, a similar value of 0.6 was observed at 12℃ and 15℃. However, DNA significantly increased beyond 18℃ (p<0.05), to a maximum of 1.8 at 24℃. DNA concentration significantly decreased to 0.6. The concentrations of RNA and total protein were likely at their highest values of 1.7 and 0.07 μg ml-¹ at 24℃, respectively. RNA and total protein concentrations began to increase at 15℃. Oxygen availability between lower and higher temperatures was significantly different and increased from 18℃ according to light intensity, regardless of wavelengths (p<0.05). At 24℃, the highest value of the maximum electron transport rate (ETRmax), ranging from 537.9 (Ch 1) to 602.5 μmol electrons g-¹ Chl a s-¹ (Ch 4), was also apparent. Nitrate reductase (NR) and ATPase activities were at their highest values of 0.11 μmol NO₂- μg-¹ Chl a h-¹ and 0.78 pmol 100 mg-¹ at 24℃, respectively. In an analysis of CHN, the concentration of C and N also significantly increased (p<0.05). Most of the measurements for the cellular activities at 27℃, however, were less than at 24℃. These results suggest that the sub-cellular activities of C. polykrikoides are sensitive to changes in water temperature. It may be desirable to estimate at 18℃ the initiation of the massive blooming development of C. polykrikoides. In nature, it will be very difficult to maintain the massive blooms beyond 24℃ because of a possibly significant decrease in molecular activity of C. polykrikoides.