Acute toxicity of N-(phosphonomethyl) glycine herbicide on planktonic microorganisms Artemia franciscana and Microcystis aeruginosa

Abstract

Continuous exposure to N-(phosphonomethyl) glycine (glyphosate) produces alterations on aquatic ecosystems, depending on the species or organism, concentration and exposure time. The aim of this research was to evaluate the median lethal concentration (LC₅₀₍₂₄₎) in Artemia franciscana, as well as the median population inhibitory concentration (IC₅₀) and the coefficient of form (CF) in the cyanobacterium Microcystis aeruginosa in aquatic ecosystems. The results for A. franciscana were an LC₅₀₍₂₄₎ 0.31 mg L^-1, and on M. aeruginosa of an IC₅₀₍₇₂₎ 53.95 mg L^-1. About the study of the coefficient of form, in the control cells of M. aeruginosa it resulted in a CF≈1, while exposed to 72h-NOEC (No Observable Effect Concentration) was 2.95 mg L^-1. The IC₅₀₍₇₂₎ was 53.95 mg L^-1 indicating that the cells remain spherical, however, there are significant changes in their volume and the cell surface exposed to IC₅₀₍₇₂₎ of 7.69 ± 1.69 µm³ with 33% volume reduction compared to the control cell, which reflects the ecotoxicological dangers of this herbicide. Exposure to glyphosate resulted as category I (highly toxic) in A. franciscana and category II (toxic) in M. aeruginosa, according to the classification of the United States Environmental Protection Agency (U.S. EPA).