Meropenem is a broad-spectrum antibiotic, formulated to combat pathogenic microorganisms in the treatment of respiratory diseases. Several studies have demonstrated the presence of carbapenem compounds in bodies of surface water and this requires monitoring to identify possible effects on non-target organisms, such as photosynthetic organisms present in aquatic ecosystems. This study evaluated the effects of the antibiotic meropenem on the determinations of growth, photosynthesis, chlorophyll, and catalase enzyme activity in organisms Synechococcus elongatus, Chlorella vulgaris, and Lemna minor. Among the findings, growth stimulation was identified in Synechococcus elongatus at concentrations <2 μg/L of meropenem. However, at concentrations of ≥ 20 μg/L the antibiotic inhibited the growth of the species. Although the antibiotic did not affect the growth rate of the Lemna minor plant at concentrations <200,000 μg/L, physiological alterations such as decreased photosynthetic rate and chlorophyll concentration were observed in plants exposed to concentrations >20 μg/L. In addition, meropenem caused an increase in the activity of the catalase enzyme as a defense mechanism against oxidative stress. The antibiotic did not significantly affect the growth of Chlorella vulgaris compared to the control group.Among the three tested species, meropenem showed greater toxicity to the cyanobacterial species, with an EC50 of 74.5 μg/L and EC20 of 9.1 μg/L. Molecular docking was done with a protein of Synechococcus elongatus and the 3WXO-meropenem complexes: depicting greater docking scores (affinity -7.7 kcal/mol) and their corresponding residue‐ligand with the histidines (His263A and His95A) of the KatG protein. That could explain the affinity of the antibiotic for the protein and to interpret the mechanism of action between the antibiotic with the cyanobacteria.