EFFECTS OF NITROGEN AND PHOSPHORUS ON THE GROWTH AND FATTY-ACID COMPOSITION OF ULVA-PERTUSA KJELLMAN (CHLOROPHYTA)

The effects of nutrient levels of nitrogen (0, 0.01, 1.5, and 15 mM as nitrate) and phosphorus (0, 1, 75, and 750 mu M as phosphate) on the growth and qualitative fatty acid composition of the green seaweed, Ul va pertusa were studied in a completely randomized laboratory experime nt using an artificial seawater medium. Nutrient (nitrogen and phospho rus) starvation resulted in loss of biomass and negative specific grow th rates on the 4th day of culture. Nitrogen starvation and very high levels of nitrogen (15 mM) increased crude lipid content (as a percent age of dry weight). Increasing the level of nitrogen decreased the pro portions of the major polyunsaturated fatty acids 16:4 n-3 and 18:4 n- 3; and increased the proportions of 16:0, 18:1 n-7 and 18:2 n-6. Nitro gen levels tested gave no significant effects on the other major fatty acids, 18:3 n-3 and 18:4 n-1. Phosphorus starvation decreased the pro portions of 16:0 and increased that of 16:4 n-3. Varying levels of pho sphorus did not produce observable changes in the crude lipid content of the seaweed. Chlorosis was observed in nitrogen-starved cultures bu t not in phosphorus-starved seaweed.