Primary production of freshwater microbial communities is affected by a cocktail of herbicides in an outdoor experiment

V.L. LOZANO; A. TORREMORELL; S. ALLEN DOHLE; H.N. PIZARRO; M.S. VERA

ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY

ACADEMIC PRESS INC ELSEVIER SCIENCE

Lugar: Amsterdam; Año: 2020

0147-6513

Primary production (PP) is a key variable to evaluate the quality of the ecological services provided by fresh- water bodies because it gives information on the amount of oxygen and organic matter incorporated into the system. We analysed the impact of a mixture of commercial formulations of glyphosate- and 2,4-D-based her- bicides (Roundup Max® and AsiMax 50®, respectively) on freshwater primary production. Primary production was studied through the oxygen exchange method. Four measurements were made during a 23-day experiment in outdoor mesocosms using the light and dark bottle method. High and low concentrations of the active in- gredients were assayed to evaluate a concentration-dependent effect. Our results indicated that the mixture of Roundup Max® and AsiMax 50® acted mostly additively on gross and net primary production. Moreover, we found a concentration-dependent effect of each herbicide on PP. Thus, AsiMax 50® at low and Roundup Max® at high concentration induced a significant early decrease in respiration and gross primary production 4 h after application, attributable to physiological responses. Besides, significant increases in primary production were simultaneously recorded with increases in chlorophyll a concentration and micro + nano-phytoplankton abundance 7 days after the application of Roundup Max® at high concentration. This study contributes to the knowledge of the impact of widely used herbicides on freshwater ecosystems.