Potential of Asparagopsis armata as a Biopesticide for Weed Control under an Invasive Seaweed Circular-Economy Framework

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.

Fluoxetine induces photochemistry-derived oxidative stress on Ulva lactuca

“…In the present study, U. lactuca exposed to increasing exogenous fluoxetine concentrations showed a significant dose-related decrease in energy absorption and trapped energy flux. A similar response has already been reported in the microalgae Phaeodactylum tricornutum, exposed to the same fluoxetine concentrations (Feijão et al, 2020), which is often associated with lower efficiency in light-harvesting and exciton energy generation from captured photons (Duarte et al, 2021d) and commonly reported in microalgal exposure to other PPCPs (Silva et al, 2020) and pesticides . The photosynthetic response seems to mirror the metabolic changes occurring in P. tricornutum, namely a decrease in the oxidized quinone pool and RC density, with a significantly increased quinone turnover and energy needed to close all RCs.…”

“…Overall, the biomarker CAP analysis demonstrated that chlorophyll a fluorescence (PAM: >70% correct classification accuracy) and oxidative stress-derived biomarkers (Oxidative stress: 100%) are the best non-invasive and invasive techniques, respectively, to assess fluoxetine exposure in U. lactuca. Bio-optical techniques such as PAM have the advantage to allow performing a non-invasive evaluation of the organisms, producing a high amount of data that can efficiently act as biomarker variables or be integrated into multivariate biomarker indexes (Duarte, et al, 2021c;Duarte et al, 2021d;Lemos, 2021), and used for exposure assessment. The assessed oxidative stress biomarkers have been demonstrated to be reliable from diatoms to plants exposed to stressors such as heavy metals, pharmaceuticals and pesticides Pires et al, 2021).…”

Effect Biomarkers of the Widespread Antimicrobial Triclosan in a Marine Model Diatom

“…Nevertheless, a significant increase in the lipid peroxidation products of the cells exposed to mild and high triclosan concentrations was detected. Observing the oxidative ratio, a promotion of the peroxidasic activity in detriment of the SOD activity [ 62 ] is evident, indicating a high generation of hydroxyl radicals by peroxidasic activity [ 63 ], which without iron-based Fenton reactions will not be efficiently quenched and prone to produce lipid hydroperoxides, thus leading to the lipid peroxidation products increase. This lack of SOD efficiency reinforces the role of carotenoid-ROS quenching mechanisms and the abovementioned carotenoid depletion.…”

Biotechnological Potential of Macroalgae during Seasonal Blooms for Sustainable Production of UV-Absorbing Compounds

“…High biofiltration capacity of nutrients; UV photoprotection [163] Exudate cocktail as a biopesticide for eco-friendly weed control [171] Preservatives, cosmeceuticals, biopharmaceuticals [117] MAAs (accumulated only under a high ammonium-N availability) [163] AS, PR, PE, SH, UN [127] Red algae Order: Gracilariales Gracilaria vermiculophylla Increase in MAAs in freshly released spores increased under UVR 8 h [172] AS, PE, PR, PI, SH, US, UN [127,166] Abbreviations: Asterina-330 (AS), Mycosporine-glycine (MG), Palythine (PI), Palythene (PE), Porphyra-334 (PR), Shinorine (SH), Unidentified MAAs (UN), Usujirene (US). Red algae-Rhodophyta; Green algae-Chlorophyta; brown algae-Phaeophyceae.…”