Hormesis and antagonism in low-dose phalaris allelochemicals during microcystis control

Journal article

Aquatic ecosystems face significant challenges globally from cyanobacterial blooms. Phalaris arundinacea (reed canary grass) is used in artificial wetlands and found in natural wetlands. We investigated whether allelochemicals released from Phalaris root exudates inhibit Microcystis aeruginosa growth. We conducted experiments to disentangle the effect of the root exudates from living plants on resource competition and the potential role of microbiota in controlling Microcystis growth. We found that allelochemicals from root exudates and their inhibitory effect decayed over time. Results from filtration experiments and microscopic observations indicated that the removal of microorganisms (≥0.22 µm) allowed the growth of Microcystis, suggesting that protists and rotifers may control Microcystis growth. We also tested commercial allelochemicals at environmentally relevant concentrations (≤1000 µg L−¹) against Microcystis. Concentrations of 1000 µg L−¹ of anthraquinone, gallic acid, gramine, hordenine, linoleic acid, naringuin, stigmasterol, tannic acid, 4-nitroindol-5-carboxaldehyde, and a mixture of the 9 allelochemicals inhibited Microcystis growth (≥87%). The minimum effective concentration was determined to be 100 µg L−¹ for most allelochemicals, except for anthraquinone, which had a hormetic effect of stimulating Microcystis growth by up to 70% compared to the controls. Our findings indicate that allelochemicals could be used to control Microcystis, but it is essential to establish the minimum effective allelochemical inhibitory concentrations from biofilters, wetlands, or macrophytes to assess their potential for managing Microcystis, other cyanobacteria, and microalgae. The increasing global use of artificial wetlands to control cyanobacterial blooms justifies further investigation into critical allelochemical concentrations, including decay trends over time and hormetic effects that occur in wetlands.

Authors: Castro-Castellon, AT; Hughes, JMR; Chipps, MJ; Hankins, NP

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Taylor & Francis
• Journal: Inland Waters
• Volume: 15
• Issue: 1
• Article number: 2426388
• Publication date: 2024-11-12
• Acceptance date: 2024-11-02
• DOI: 10.1080/20442041.2024.2426388
• EISSN: 2044-205X
• ISSN: 2044-2041
• Language: English
• Keywords: anthraquinone; aquatic ecosystems; constructed wetland; scyanobacteria management; macrophytes; root exudates