Abstract
Marine macroalgae have been increasingly targeted as a source of bioactive compounds to be used in several areas, such as biopesticides. When harvesting invasive species, such as Asparagopsis armata, for this purpose, there is a two-folded opportunity: acquiring these biomolecules from a low-cost resource and controlling its spreading and impacts. The secondary metabolites in this seaweed's exudate have been shown to significantly impact the physiology of species in the ecosystems where it invades, indicating a possible biocidal potential. Considering this in the present work, an A. armata exudate cocktail was applied in the model weed Thellungiella halophila to evaluate its physiological impact and mode of action, addressing its potential use as a natural biocide. A. armata greatly affected the test plants' physiology, namely, their photochemical energy transduction pathway (impairing light-harvesting and chemical energy production throughout the chloroplast electron transport chain), carotenoid metabolism and oxidative stress. These mechanisms of action are similar to the ones triggered when using the common chemical pesticides, highlighting the potential of the A. armata exudate cocktail as an eco-friendly biopesticide.