Effect of glyphosate acid on periphyton exposed in outdoor microcosms

IUMMATO M.M.; RIOS DE MOLINA, MC; PIZARRO H; CATALDO D.; DI FIORI E.; JUAREZ AB

BUENOS AIRES

Congreso; SETAC Latin America 11th Biennial Meeting; 2015

SETAC

Nowadays, the agricultural technologies are associated with intensive and sustained use of agrochemicals. The runoff and aerial drift phenomena put the water bodies bordering agricultural lands in a vulnerable situation, by determining the entry of herbicides that impact their communities. Periphyton is a complex aquatic microbial community with many attributes that makes it a useful early bioindicator of pollution. The outdoor microcosms are important models, because they allow mimic the effect on natural communities. In this study the effects of glyphosate acid (GlpA) on the growth and metabolism of periphyton exposed to 0, 1, 3 and 6 mg GlpA/l with and without bivalves (Limnoperna fortunei) presence were evaluated. The experiment was carried out on outdoors microcosms. The experimental design aimed to recreate the impact of a time period of exposure to GlpA (26 days) similar to the elapsed time between two applications of the pesticide in an agricultural scheme. The impact of GlpA on biomass, carotene/chlorophyll a ratio and oxidative stress parameters was evaluated at 1, 7, 14 and 26 days of exposure. In microcosms without bivalves, it was observed an increase of total biomass of periphyton (ashfree dry weight) with 1 mg GlpA/l at day 26 (probably hormesis effect) and a diminution with 6 mg/l at 26 day (inhibitory effect). However, a differential effect on autothrophic biomass was occurred, evidenced by an increase of clorophyll a/cm2 with all GlpA concentrations at days 7, 14 and 26. The carotene/chlorophyll a ratio showed significant diminutions respect to the controls with all GlpA concentrations at 14 and 26 days of exposure. This would indicate an alteration in the structure of the photosystems in periphytic algae. The lipid peroxidation levels showed a significant increse respect to the controls in periphyton exposed to 1, 3 and 6 mg/l at day 7. The antioxidant enzymes catalase and superoxide dismutase showed activities significant lower than the controls with all GlpA concentrations at days 7, 14 and 26 days. Results indicates alterations in oxidative stress parameters, wich could indicate their participation in the effect exerted on the whole periphytic community (heterotrophic and autotrophic fractions). In microcosms with bivalves, all the effects were ameliorated, observing values similar to the controls for all parameters analyzed. This could relate to the fall of glyphosate by filtering activity of bivalve.