Glyphosate Accelerates the Proliferation of Microcystis aeruginosa, a Dominant Species in Cyanobacterial Blooms

Abstract

Glyphosate is a commonly used herbicide known for its high performance in killing certain plants and grasses; however, its use is regulated due to its harmful effects on the aquatic environment. The present study investigated and compared the toxic mechanisms of glyphosate on Microcystis aeruginosa (a toxin‐producing cyanobacterium) under 2 conditions: 0‰ saline media (experiment I) and 2.5‰ saline media (experiment II). The results indicated that an appropriate concentration of glyphosate provided a phosphate source for M. aeruginosa, resulting in an increased specific growth rate in both experimental groups compared with the controls. Glyphosate‐enhanced alkaline phosphatase (ALP) activity increased by up to 1.37‐fold in experiment I and 1.68‐fold in experiment II. Moreover, the activities of superoxide dismutase (SOD) and catalase (CAT) decreased at glyphosate concentrations below 1.2 mg L–1 but increased at concentrations greater than 1.2 mg L–1 in experiment I, whereas SOD and CAT activities decreased in experiment II and declined by 64 and 49% in the 30 mg L−1 treatments. Furthermore, the transcript abundances of the pyruvate carboxylase (pcB), microcystin synthetase B (mcyB), and paired‐like homeobox (phoX) genes were up‐regulated by up to 6.92‐, 3.63‐, and 2.27‐fold in experiment I and 6.74‐, 6.55‐, and 4.86‐fold in experiment II after 96 h of incubation. The addition of glyphosate stimulated the production of dissolved organic matter including tryptophan‐like substances, fulvic acid‐like substances, (marine) humic acid‐like substances, and microcystin–leucine‐arginine in the culture. In conclusion, glyphosate stimulates the proliferation of M. aeruginosa and enhances the release of dissolved organic matter in saltwater ecosystems. Environ Toxicol Chem 2021;40:342–351. © 2020 SETAC

A perspective on how glyphosate and 2,4-D in wetlands may impact climate change

“…Due to glyphosate's chemical structure, its degradation often contributes substantial amounts of phosphorus (P), which has been found to be favored and more rapidly utilized by microorganisms compared to other sources of soil P (Hébert et al, 2019;Sun et al, 2019). Specifically, stimulated cyanobacterial growth and cyanotoxin production has been recorded from glyphosate-derived P enrichment (Vera et al, 2010;Qiu et al, 2013;Zhang et al, 2016;Hernández-García and Martínez-Jerónimo, 2020;Wang et al, 2021;Lin et al, 2023). Glyphosate degradation was found to be positively correlated with total P concentrations in surface waters (Carles et al, 2019).…”

A Perspective on How Glyphosate and 2,4-D May Impact Climate Change

“…Due to glyphosate's chemical structure, its degradation often contributes substantial amounts of phosphorus (P), which has been found to be favored and more rapidly utilized by microorganisms compared to other sources of soil P (Hébert et al, 2019;Sun et al, 2019). Specifically, stimulated cyanobacterial growth and cyanotoxin production has been recorded from glyphosate-derived P enrichment (Vera et al, 2010;Qiu et al, 2013;Zhang et al, 2016;Hernández-García and Martínez-Jerónimo, 2020;Wang et al, 2021;Lin et al, 2023).…”