Effects of heavy metals and light levels on the biosynthesis of carotenoids and fatty acids in the macroalgae Gracilaria tenuistipitata (var. liui Zhang & Xia)

We present here the effect of heavy metals and of different light intensities on the biosynthesis of fatty acids and pigments in the macroalga Gracilaria tenuistipitata (var. liui Zhang & Xia). In order to verify the fatty acid content, gas chromatography with flame ionization detection (GC-FID) was employed. Pigments (major carotenoids and chlorophyl-a) were monitored by liquid chromatography with diode array detection (HPLC-DAD). Cultures of G. tenuistipitata were exposed to cadmium (Cd2+, 200 ppb) and copper (Cu2+, 200 ppb), as well as to different light conditions (low light: 100 μmol.photons.m- 2.s-1, or high light: 1000 μmol.photons.m-2.s-1). Cd2+ and Cu2+ increased the saturated and monounsaturated fatty acid content [14:0, 16:0, 18:0, 18:1 (n-7) and 18:1 (n-9)] and all major pigments (violaxanthin, antheraxanthin, lutein, zeaxanthin, chlorophyll-a and β-carotene). Both heavy metals decreased the levels of polyunsaturated fatty acids (PUFA) [18:2 (n-6), 18:3 (n-6), 18:5 (n-4), 20:4 (n-6), 20:5 (n-3), 22:6 (n-3)]. G. tenuistipitata cultures were exposed to high light intensity for five days and no statistically significant differences were observed in the content of fatty acids. On the other hand, the levels of pigments rose markedly for chlorophyll-a and all of the carotenoids studied.