Eicosapentaenoic acid content of Skeletonema costatum as a function of growth and irradiance; Relation with chlorophyll a content and photosynthetic capacity

Eicosapentaenoic acid (20:5(n-3)) and chlorophyll a contents were examined during the growth of Skeletonema costatum batch cultures. When the results were normalized to dry weight, it was shown that the 20:5(n-3) content and the Chl a content were maximum at the end of the logarithmic growth phase. The rate of photosynthetic oxygen evolution showed a similar pattern of change. The influence of irradiance on 20:5(n-3) content was also investigated: lower the irradiances, higher the dry weight related 20:5(n-3) content, as well as the Chl a content and the rate of photosynthetic oxygen evolution. These results suggested that the abundance of 20:5(n-3) associated with the specific pigment could be related to the photosynthetic activity. When the results were related to dry weight, the ratio of the 20:5(n-3) to Chl a contents seemed to be correlated to the photosynthetic rate. When the results were reported to % molar of total fatty acids, the 20:5(n-3) content did not seem to vary at the same extent.