Fatty Acids as Indicators of Environmental Condition in Microalgae

International audience; Fatty acids (FA) were widely used as taxonomic indicators to distinguish algal groups by the presence, the abundance and the distribution of particular FA. This work aimed to compare between species FA composition of three green algae (Chlorophyceae: Chlorella vulgaris, Pseudokirchneriella subcapitata and Scenedesmus subspicatus) grown under comparable conditions, and to assess the suitability of using FA as indicators of taxonomic groups and environmental conditions for microalgae. Results showed that FA composition could not be used as a taxonomic feature of particular species because close species may present different FA composition due to their physiological state which in turn depends on environmental conditions. In this context, FA should be used as indicator at the class rather than the genus and/or species level. We propose two FA indices, the ω3/ω6 polyunsaturated FA ratio and an unsaturation index as indicators of physiological state and the growth phase of algae and a signs of changing environment.