EFFECTS OF TEMPERATURE, LIGHT-INTENSITY, SALINITY AND SOURCE OF NITROGEN ON THE GROWTH, TOTAL LIPID AND FATTY-ACID COMPOSITION OF ULVA-PERTUSA KJELLMAN (CHLOROPHYTA)

Growth, total lipid content and fatty acid composition of Ulva pertusa Kjellman were studied in a 4 x 2 factorial laboratory experiment at two levels (low and high) of temperature (15 and 25-degrees-C), subsaturating light intensities (16 - 32 and 48 - 64 muE m-2 s-1), salinity (20 and 359 parts per thousand) and two sources of nitrogen (nitrate and ammonia). Specific growth rate (SGR) was highest at low temperature (15-degrees-C), high light intensity (48 - 64 muE m-2 s-1) and high salinity (35 parts per thousand). Interaction between temperature, light intensity and nitrogen source was the highest source of variation in SGR at the beginning of culture, while salinity and salinity-light intensity interactions were the most limiting factors during the later part of culture. Effect of nitrogen source (with a preference for ammonia) was significant only during the early part of culture. Moisture content was increased at low light intensity. Total lipid content (both as percent of fresh and dry weights) increased at low temperature and high salinity. Low temperature increased levels (as % of total fatty acids) of oleic (18 : 1n-9) and linolenic (18 : 3n-3) fatty acids. High light intensity increased levels of palmitic acid (16 : 0), the most abundant fatty acid. Low light intensity (16 - 32 muE m-2 s-1) increased levels of the tetra-unsaturated fatty acids 16 : 4n-3 and 18 : 4n-3. High salinity increased the levels of the C16 and C18 poly-unsaturated fatty acids.