Bioconcentration of glyphosate in wetland biofilms

Wetland biofilms were exposed to the herbicide glyphosate via in situ field exposures and controlled microcosm experiments to measure bioconcentration and metabolism of glyphosate by biofilm organisms. Concentrations of glyphosate in biofilms were two to four orders of magnitude higher than the surrounding water, bioconcentration factors averaged 835 and 199 L. kg(-1) in field- and lab-exposed biofilms, respectively. Glyphosate in water where it had been detected in biofilms at field-exposed sites ranged from below detection (<1 mu g.L-1) up to 130 mu g.L-1. Bioconcentration of glyphosate in biofilms was inversely proportional to concentrations in the surrounding water, and the retention kinetics were similar to both adsorption and enzymatic models. Microorganisms present in both the water and biofilms metabolized glyphosate to its primary breakdown product aminomethyl phosphonic acid (AMPA), with increased rates of breakdown in and around the biofilms. Photosynthetic efficiency of the algae within the biofilms was not affected by 24 h controlled glyphosate exposures. Our results demonstrate the role of biofilms in improving wetland water quality by removing contaminants like glyphosate, but also as a potential exposure route to higher trophic levels via consumption. Due to bioconcentration of pesticides, exposure risk to organisms consuming or living in biofilms may be much higher than indicated by concentrations in ambient water samples. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

The study found that wetland biofilms can remove contaminants such as glyphosate through bioconcentration and metabolism. The concentrations of glyphosate in biofilms were several orders of magnitude higher than in the surrounding water, and bioconcentration factors and metabolic patterns indicated that biofilms have the ability to degrade and absorb glyphosate.