Effects of salinity and temperature on the acute toxicity of the pesticides, dimethoate and chlorpyrifos in post-larvae and juveniles of the whiteleg shrimp

Abstract

In this article, the acute toxicity of the organophosphorus pesticides (OPs), dimethoate (DMT) and chlorpyrifos (CPF) in post-larvae, and juveniles of Litopenaeus vannamei at different ambient salinity (5, 15 and 25) and temperature (15, 25 and 34 °C) regimes were compared with standard exposure conditions (temperature, 27 °C and salinity, 20). Chlorpyrifos was significantly more toxic to both life stages (P < 0.05). Post-larvae were more sensitive than juveniles to both OPs in all altered salinities and temperatures (P < 0.05). Acute toxicity indices (96 h LC50 values) showed that lower salinities (5 and 15) and temperature (15 °C) induced significantly higher pesticide toxicity (P < 0.05) in both life stages. Very low acute toxicity indices of DMT and CPF at varying levels of salinity and temperature highlight the importance of monitoring OPs pollution in low-saline shrimp aquaculture ponds. Results of the present study provide baseline information for monitoring pesticide pollution in low-saline shrimp aquaculture ponds which are influenced by changes in climatic conditions. Keywords: Dimethoate, Chlorpyrifos, Shrimp aquaculture, Climate change, Toxicity