Ecotoxicology of Copper on Freshwater Fish with Different Water Hardness on the Mekong River, Lao PDR

Abstract

The aquatic resources of the Mekong River are important to support the livelihoods of a large percentage of 60 million or more people living in the Lower Mekong Basin. A study on the impact of heavy metals on tropical freshwater fish in the Mekong River is needed. Ecotoxicology of copper on freshwater fish was studied using field-collected water from two local sites along the Lower Mekong Basin in Lao PDR, which focused on two different water hardness. In this study, US EPA method was used for the acute toxicity test to larvae Labeo rohita with 7 different copper concentrations (0, 0.02, 0.09, 0.16, 0.23, 0.3, and 0.37mg/L) in moderately hardness of water (108±0.00mg/L as CaCO₃) and (0, 0.02, 0.03, 0.04, 0.05, 0.09, and 0.13mg/L) in soft hardness of water (20±2.83mg/L as CaCO₃). The mortalities of fish were observed at 24, 48, 72, and 96 hr. The results clearly showed that amount of mortalities were increased from low to high copper concentrations. The 96-hr LC₅₀ values of copper on larvae L. rohita with moderately hardness and soft hardness of water were 0.106 and 0.038 mg/L, respectively.