Toxicological effects of atrazine in Cnesterodon decemmaculatus.

MARIA FLORENCIA NUÑEZ CRESTO; CRISTINA PÉREZ-COLL; GABRIELA SVARTZ

Montevideo

Congreso; SETAC Latin America 15th Biennial Meeting.; 2023

SETAC LA

Atrazine is one of the most used herbicides in the last decades, and it is frequently detected in different water bodies, both shallow and underground. Toxicity assessments in non-target species are important to evaluate unintended risks in the environments. Many studies have shown the potential risks of atrazine in aquatic organisms, such as endocrine disruptive effects, mortality and neurotoxicity. The purpose of this study was to evaluate the lethal and sublethal effects of this herbicide in Cnesterodon decemmaculatus, a native fish species that can be found in many water bodies in South America. To achieve this, a series of semistatic standardized bioassays were performed during acute (96 h) and subchronic (336 h) periods of time. Adult fish were randomly distributed between 8 concentrations between 0.5 and 100 mg a.i./L of a commercial formulation of atrazine (Atramyl® 90 WG) in 1 liter tanks with 10 individuals in each. Each assay was conducted by triplicate and controls with dechlorinated water were simultaneously maintained. During the exposure periods, ethological changes were recorded daily for each concentration. The LC-50s obtained were 77.46, 4.03, 56.77, 45.96 and 13.61 for 24, 96, 192, 264 and 336 h respectively. Mortality was reported at 24 h in 100 mg/L (LOEC-24h). At 96 hours, 60 mg/L was the highest concentration in which there was no observable effect (NOEC-96h). From 192 to 264 h, the NOEC value was 40 mg/L, and at 336 h it was 10 mg/L. Regarding behavioural alterations, these were observed from 10 mg/L and included lethargy, lack of equilibrium or erratic swimming and natation in the surface of the tank. These results further accentuate the toxicological effects of atrazine in aquatic organisms, both lethal and sublethal. Additionally, these findings highlight the importance of strict regulations regarding the usage of atrazine and other pesticides near water bodies, in order to avoid unintended effects in the ecosystems.