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 degrees C) regimes were compared with standard exposure conditions (temperature, 27 degrees C and salinity, 20). Chlorpyrifos was significantly more toxic to both life stages (P less than 0.05). Post-larvae were more sensitive than juveniles to both OPs in all altered salinities and temperatures (P less than 0.05). Acute toxicity indices (96 h LC sub(50) values) showed that lower salinities (5 and 15) and temperature (15 degrees C) induced significantly higher pesticide toxicity (P less than 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.