Acute toxic effect of glyphosate on Pomacea canaliculata under the condition of oxidative deposition

Objective  To explore the acute toxic effect of glyphosate on Pomacea canaliculata under the combined pollution of glyphosate and H₂O₂.

Method  Using the hydrostatic biological test method, adult Pomacea canaliculata with uniform growth in the field were collected, and exposed to water with different concentrations of glyphosate and similar to the average concentration of H₂O₂ (50 μmol·L⁻¹) in precipitation of Guangzhou. The influences of glyphosate on some water quality indexes of P. canaliculata habitat and acute toxic effects of P. canaliculata under oxidative deposition conditions were studied.

Result  For the water quality index, oxidation-reduction potential (ORP) increased with the increase of exposure time, from 330 mV to about 540 mV; The change of pH with the increase of exposure time increased or decreased under different treatments, and finally maintained between 7.0 and 8.5; The concentration of dissolved oxygen (DO) was between 8.5 and 16.0 mg·L⁻¹, and there was no obvious variation trend. The three water quality indexes above were within the range that the growth of P. canaliculata could adapt to. Acute toxicity tests indicated that glyphosate had low toxicity to P. canaliculata, and the 50% lethal concentration (LC₅₀) in 48 h was 133.479 mg·L⁻¹ with or without H₂O₂ deposition. The anti-oxidative stress enzymes of superoxide dismutase (SOD) and catalase (CAT), as well as energy metabolism-related enzymes of amylase (AMS) and lipase (LPS) in P. canaliculata were firstly up-regulated, then suppressed, and finally adapted to up-regulation. It showed that in the process of poisoning, P. canaliculata could slowly adapt to the stress environment and continuously improve its stress resistance, so that it could survive normally in this stress.

Conclusion  Under the condition of oxidative deposition, the acute toxic effect of glyphosate on P. canaliculata is low, and the activities of the four related typical enzymes are generally up-regulated. It is ineffective and unrealistic to try to inhibit P. canaliculata through herbicide weeding at the same time.