Climate change – herbicides interactions on lipid biochemistry

Fatty acid (FA) synthesis and trophic transfer along aquatic food webs are essential for proper development of organisms, yet both can be attenuated by environmental factors, such as increasing temperature and exposure to xenobiotics (e.g., herbicides). While aquatic primary producers and consumers typically contain higher contents of polyunsaturated fatty acids (PUFA) at low temperatures, the presence of herbicides (e.g., atrazine, S-metolachlor) can significantly decrease the PUFA content in aquatic organisms. However, the effects of the interaction between natural temperature fluctuations (e.g., daily temperature fluctuations, DTF) and exposure to herbicides on FA synthesis and subsequent trophic transfer in freshwater ecosystems are poorly understood. At present, most studies on environmental stressors in aquatic food webs use steady temperature conditions and thus fall short in understanding the effects of naturally occurring temperature variations. Such approach is very simplistic, and results of such studies might thus be misleading to predict the ecotoxicological effects of herbicides on organisms in aquatic ecosystems. To fill this knowledge gap, this research aims to understand the ecophysiological dynamics of these essential dietary nutrients in a changing environment, by examining the effects of DTF and exposure to herbicides on FA synthesis and trophic transfer of organisms across aquatic food webs at multiple generations (long-term) and multi-taxa scales. We will track changes in the lipid profiles of algae and zooplankton, by applying compound-specific stable isotope analysis of FA, and predict that polar (membrane) lipids will be isotopically modified, while storage (neutral) lipids remain isotopically unaltered. Under the current scenario of global warming that affects water temperature and the amplitude of the DTF as well as the ecophysiological fate of herbicides, this research will considerably further, at mechanistic scales, our understanding of climate change-induced action of contaminants on essential nutrients of organisms at the base of freshwater food webs. Our findings will thus contribute to establish future directives on herbicide best practices at the terrestrial (agriculture)-aquatic food web interface, aiming at minimizing toxic effects and optimizing the FA synthesis and trophic transfer under various realistic herbicide stress in aquatic ecosystems.