THE FATTY-ACID COMPOSITION OF SEAWEEDS EXPOSED TO DIFFERENT LEVELS OFLIGHT-INTENSITY AND SALINITY

Three seaweeds Ulva pertusa (Chlorophyta), Grateloupia sparsa (Rhodoph yta) and Sargassum piluliferum (Phaeophyta) were exposed to combinatio ns of 2 light intensities (15 and 60 mu E m(-2) s(-1)) and 3 salinitie s (10, 35 and 50 parts per thousand) in a 2 x 3 factorial experiment t o examine the effects on their fatty acid (FA) profiles. In Ulva, expo sure to the high light intensity and low salinity combination resulted in huge decreases in the quantitative (mgg(-1) dry weight) total FA c ontent. High light intensity increased the quantitative levels of most saturated FAs (14:0, 15:0, 16:0 and iso-17:0). In Grateloupia, low an d high salinity exposure resulted in significant increases in the tota l FA content, total polyunsaturated FAs, total saturates and total mon oenes compared to normal salinity (35 parts per thousand) exposure. Hi gh light intensity increased the quantitative levels of 14:0, 18:1 n-9 , 18:1 n-7, 20:5 n-3 and total n-3. In Sargassum, high light intensity resulted in a decrease in the quantitative levels of almost all FAs. A trend of increasing levels of 18:4 n-3, 20:4 n-6, 20:5 n-3, total n- 3 and total n-6 FAs were observed with increasing salinity. Exposure t o high salinity in Ulva and Sargassum, and low and high salinities in Grateloupia resulted in significantly higher levels of total FAs compa red to unexposed fresh seaweeds. Changes in the quantitative FA conten t of Ulva were a consequence of light and/or salinity-controlled growt h rates.