Lipid composition of phytoplankton from the Barents Sea and environmental influences on the distribution pattern of carbon among photosynthetic end products

Abstract

The colonial algae Phaeocystis pouchetii and Dinobryon pellucidum dominated the phytoplankton crop at three stations in the Polar Front area of the Barents Sea. Lipid extracted from the seawater containing the phytoplankton was dominated by neutral lipid classes, particularly triacylglycerols, and phospholipids were more abundant than galactolipids at all stations. Polyunsaturated fatty acids comprised between 15 and 26% of fatty acids of total lipid. Of the carbon assimilated into lipid over 24 hours, 40% was located in the neutral lipid fraction. Phospholipids contained a smaller proportion of fixed carbon than galactolipids. No defiinte relationships were observed between the distribution of fixed carbon in photosynthetic end products and the temperature or irradiance at which the phytoplankton was incubated. At a constant irradiance of 8.5 ?mol m?2s?1, the highest proportion of fixed carbon was recovered in protein at 4.5°C, but at ?1.5°C most radioactivity was present in low molecular weight compounds. Regardless of incubation conditions, lipid always contained less than 30% of total assimilated carbon.