Biomarkers of oxidative stress in Bidens laevis for analyzing pollution by current use pesticides in La Brava lake (Argentina)

Abstract

La Brava lake is a protected landscape by the Provincial Agency for Sustainable Development of Buenos Aires Province (OPDS), Argentina. Despite this status, the lake is surrounded by important agricultural activities. The aim of the present study was to evaluate the pollution by current use pesticides (CUPs) in surface water of La Brava basin using biomarkers of oxidative stress in the aquatic macrophyte Bidens laevis. Two samplings per year were performed in Tajamar creek, one in spring and the other in summer when peak pesticides concentrations were expected. Samplings were performed for two consecutive years. Each time, macrophyte samples (n=10) for biomarkers analysis and surface water (n=3) for pesticides quantification using UPLC- MS/MS, were collected. Catalase (CAT), glutathione reductase (GR), and guaiacol peroxidase (POD) activity, as well as levels of hydrogen peroxide (H2O2) and malondialdehyde (MDA) in roots and leaves were spectrophotometrically analyzed. In the first year, in spring the herbicide glyphosate (3.5 µg/L) and the insecticide chlorpyrifos (0.7 µg/L) were detected while in summer glyphosate (2.0 µg/L), its metabolite AMPA (2.7 µg/L) and chlorpyrifos (2.4 µg/L) were detected. Leaf tissues presented higher levels of H2O2 and MDA as well as higher activities of GR but lower activity of POD in summer than in spring. Roots tissues showed higher levels of H2O2 and MDA and lower activities of CAT and POD in summer, in comparison to spring. In the second year, only chlorpyrifos in spring (3.1 µg/L) and summer (1.5 µg/L) was found. In both analyzed tissues, higher activity of POD, lower levels of H2O2 but higher levels of MDA in summer than in spring were detected. These results show that the oxidative stress biomarkers in summer increased respect the spring, mainly the oxidative damage, according to the highest levels of CUPs detected in La Brava lake. More studies will be carried out to elucidate the direct relationship between the CUPs and the adverse effects in B. laevis.