Lipid composition of the red alga Tichocarpus crinitus exposed to different levels of photon irradiance.

We examined variations in the lipid composition of the marine red alga Tichocarpus crinitus exposed to different levels of photon irradiance: 70-80% and 8-10% of the incident photosynthetically active radiation (PAR). The content of storage and structural lipids was significantly affected by the light intensity. Exposure of T. crinitus to low light conditions induced an increase in the abundance of structural components of the cell membranes, especially sulfoquinovosyldiacylglycerol, phosphatidylglycerol (PG) and phosphatidylcholine, while growth of algae at high light intensity resulted in a 1.5-folder increase in the level of storage lipids, i.e. triacylglycerols. There were no significant differences in the fatty acid composition of the total lipid pool in algae grown under different light conditions. However, the content of the most unsaturated acid, 20:5n-3, was slightly higher in T. crinitus under 8-10% PAR compared to those at 70-80% PAR. Each lipid class was found to have a characteristic fatty acid composition. The relative proportions of fatty acids esterifying monogalactosyldiacylglycerol (MGDG) and PG were significantly affected by irradiance conditions. Exposure of algae to low light resulted in increase in the content of 20:5n-3 in MGDG and in decrease in the level of this acid in PG. The concentration of trans-16:1 acid in PG increased in algae grown under high light intensity. Light conditions influenced on total lipid content, which made up 4.2+/-0.5 and 3.4+/-0.3 mg g-1 fresh weight in algae exposed to 8-10% PAR and 70-80% PAR, respectively. We suggest that variations in the lipid composition of T. crinitus exposed to different levels of light intensity may be a response of alga to light conditions and it can be considered as one of the mechanisms of adaptation of T. crinitus to varying incident light intensity.

Effect of diesel fuel pollution on the lipid composition of some wide-spread Black Sea algae and invertebrates.

Two green algae (Ulva rigida and Cladophora coelothrix), the mussel Mytilus galloprovincialis and the snail Rapana thomasiana from the Bulgarian Black Sea shore have been treated with diesel fuel (100mg l(-1)) in an aquarium with sea-water for three days. The lipids and their fatty acid changes have been examined. Significant changes have been observed mainly in the polar lipids and in the saturation of the fatty acids. These changes appeared to be bigger in the evolutionary less advanced species from both groups of marine organisms--algae and invertebrates (Ulva rigida and Mytilus galloprovincialis respectively). The data obtained could be used for a biomonitoring of the pollution.