Acute and chronic effects of the herbicide clomazone over the apple snail Pomacea sp.

The intensification of industrial agriculture has resulted in an increased utilization of agrochemicals, a significant proportion of which enter aquatic ecosystems via surface run-off, exerting an impact on non-target species. The consequences of acute intoxication are well-documented, however sub-lethal exposure is a less well-researched topic. The present study provides an experimental evaluation of the lethal and sub-lethal effects of clomazone, a widely used herbicide, on the apple snail Pomacea sp. In the initial series of trials, the organisms were exposed to four nominal concentrations of clomazone (0, 4.86, 9.25 and 15.93 mg L⁻¹) for of 96 h to evaluate mortality and determine the lethal concentration (LC₅₀). In addition, sub-lethal responses such as behavioral activity, oxygen consumption (OC), ingestion rate (IR), ammonia excretion rate (AER) and growth were evaluated after being exposed for 76 days to concentrations of 15 and 150 µg L⁻¹. The LC₅₀ for clomazone was 14.59 mg L⁻¹ (95% CI: 13.67-15.51). A significant (p < 0.05) dose-dependent reduction in both behavioral activity (quantified as area under the curve, AUC) and OC was observed in the short term. In contrast, during chronic exposure at 150 µg L⁻¹, no significant changes in OC, AER, IR, or growth were registered along the whole period. These findings, based on a multi-endpoint approach, suggest that physiological and behavioral responses of Pomacea sp. are sensitive to clomazone exposure. This highlights the species' potential as a bioindicator, but more studies are needed to explore their responses at multiple levels and life stages to develop environmental management tools in the context of risk assessment.