Fatty acid patterns of the kelps Saccharina latissima,Saccorhiza polyschides and Laminaria ochroleuca: Influence of changing environmental conditions

Kelps play a key role in coastal ecosystems and exhibit great potential as feedstock of valuable compounds with potential biotechnological applications. This study established the fatty acid patterns of Saccharina latissima (Linnaeus) C.E. Lane, C. Mayes, Druehl & G.W. Saunders, Saccorhiza polyschides (Lightfoot) Batters, and Laminaria ochroleuca Bachelot de la Pylaie, subjected to seasonal variations, from different sources (wild and aquaculture), and cultivated at different depths at sea. Stipes, blades and whole specimens were studied. S. latissima and S. polyschides specimens exhibited a higher total fatty acid content during the colder winter months and a general tendency of decreasing unsaturation towards the warmer ones. An inverse trend was found for L. ochroleuca samples. Total fatty acid content of S. latissima stipes and blades increased by over 21.5% and 31.4% with increasing depth, respectively. There were also distinct within-thallus variations, S. latissima blades exhibiting generally higher total fatty acid amounts and slightly more n-3 polyunsaturated fatty acids (PUFA) than stipes. The whole specimens of S. polyschides and L. ochroleuca grown in an integrated multi-trophic aquaculture (IMTA) system revealed no significant differences of fatty acid content compared to the ones collected at sea. Conversely, in S. latissima from IMTA the content of fatty acids per dry weight was nearly 60% higher than in the ones from natural wild stocks, registering a large increase in the amount of the most appreciated health beneficial PUFA, cis-5,8,11,14,17-eicosapentaenoic acid (C_20:5n-3c), and a significant decline in the n-6/n-3 ratio, making these edible algal specimens potentially adequate for nutritional purposes. Altogether, our results reinforce the major contribution of surrounding environmental conditions, as well as of species-specific factors, in the chemical composition of algal material. Furthermore, it encourages the optimization of culture conditions and the careful selection of algal thallus sections to improve the recovery of natural valuable compounds.