Multi-biomarker evaluation of the effects of a glyphosate-based commercial formulation and its active ingredient on the green microalga Scenedesmus vacuolatus.

Glyphosate ranks among the most widely used herbicides worldwide. When it enters water bodies, it can affect non-target organisms such as algae. This study evaluated the effects of a commercial formulation of glyphosate (CFG) and its active ingredient, isopropylamine salt of glyphosate (IPAG), on the growth, biomass, and biochemical parameters of the green microalga Scenedesmus vacuolatus. S. vacuolatus was exposed to IPAG (at concentrations of 150, 250, and 350 mg/L) and CFG (at concentrations of 4, 6, and 8 mg a.p./L) for 96 h. The concentrations causing a 50% growth inhibition were 326.11 mg/L for IPAG and 4.43 mg a.p./L for CFG. Exposure to IPAG led to decreased growth rates and total chlorophyll content compared to the controls. Likewise, exposure to the CFG resulted in decreased growth rates and total chlorophyll content, with increases in cell volume. Furthermore, IPAG-exposed S. vacuolatus showed increased levels of oxidized proteins, carotene/chlorophyll a ratio, glutathione (GSH) content, and activities of superoxide dismutase (SOD), catalase (CAT), and glutathione-S-transferase (GST) compared to controls. CFG-exposed S. vacuolatus showed increased thiobarbituric acid reactive substances (TBARS) content, oxidized proteins, carotene/chlorophyll a ratio, GSH content, and carotene content, along with decreased SOD, CAT, and GST activities compared to controls. These results indicate that both the CFG and IPAG negatively affected S. vacuolatus, altering its growth and metabolic parameters, including oxidative stress markers. Furthermore, the commercial formulation caused more toxic effects than the active ingredient alone, leading to greater alterations at lower glyphosate concentrations.