Tracing the flow of energy in food webs and unraveling the factors that control these energy fluxes are of main importance in ecology. Among all levels of the food web (plants, herbivores, carnivores) the plant-animal interface is the most variable and least predictable link. Recently, polyunsaturated fatty acids (PUFAs) have been identified as key factors modulating the efficiency of energy transfer at the plant-animal interface. Despite their wide range of physiological functions, only few organisms (primary producers, some fungi species) are able to produce them de novo. However, there are indications that harpacticoids (benthic copepods, Crustacea) have the capacity to biosynthesize certain PUFAs. My research aims to further explore the fatty acid bioconversion and biosynthesis mechanisms in harpacticoid copepods (benthic copepods, Crustacea) and the role of certain environmental variables (temperature, food quality/ quantity) in these processes. In order to meet these objectives, sampling campaigns at several latitudes (Antarctica, tropics,…) are planned. Harpacticoid copepods are important first level consumers and form an important food source for juvenile fish. Therefore, better knowledge on their PUFA metabolism might help us face upcoming challenges related to our growing human population and to fundamental ecosystem changes caused by global warming.