Climate change-herbicides interactions on lipid biochemistry

Polyunsaturated fatty acids (PUFA) are essential for human health and in particular long-chain PUFA generally considered to originate from aquatic ecosystems. Yet, the production and trophic transfer of such beneficial compounds in freshwater food webs are deeply affected by environmental factors, and can be attenuated by, for example, increasing temperature and exposure to xenobiotics (e.g., pesticides). Previous studies demonstrate that the PUFA content in primary producers (e.g., phytoplankton) and consumers (e.g., zooplankton) increased with lower temperature, and decreased with the presence of pesticides (e.g., Atrazine, S-metolachlor). However, little is known how the interaction between temperature and exposure to pesticides affects the production and the transfer of PUFA in aquatic food webs. In addition to this uncertainty, most studies on environmental stressors used steady temperature conditions and thus fall short of understanding the effects of naturally occurring temperature variation (e.g., daily temperature fluctuation). Consequently, the results of such studies might be misleading in assessing the environmental risk associated with pesticide application on the production and trophic transfer of fatty acids in aquatic food webs. To fill this knowledge gap, this research project (HerbiFat) aims to understand the ecophysiological dynamics of these essential dietary nutrients in a changing environment by examining the combined effects of daily temperature fluctuations and exposure to pesticides on the production and trophic transfer of PUFA at the base of the aquatic food web. To achieve this objective, we will perform indoor laboratory experiments and track changes in lipid profiles of phytoplankton and zooplankton by investigating compound- specific stable hydrogen isotopes of fatty acids along with other ecophysiological endpoints, such as reproduction and mortality. We predict that structural fatty acids will be isotopically modified as a response to environmental stressors, while dietary storage lipids remain isotopically unchanged. Under the current scenario of global warming that affects water temperature and its interaction with pesticides on organisms, this research will considerably further our understanding of climate change-induced action of contaminants on ecophysiological dynamics of essential dietary nutrients at the base of aquatic food webs. The findings of this research will thus contribute to establishing future directives on pesticide best practice at the terrestrial (agriculture)-aquatic food web interface, aiming at minimizing toxic effects and optimizing the production and trophic transfer of fatty acids under realistic environmental stresses in aquatic ecosystems. This project is led by Dr. Fan Qin from the trophic ecology lab of Prof. Martin Kainz at the University for Continuing Education Krems, in collaboration with the ecotoxicology lab of Dr. Isabelle Lavoie at INRS in Canada.