Ecotoxic Effects of Heavy Metals on Daphnia magna and Paracheirodon innesi in an Amazonian Peruvian River

The Madre de Dios River, in the Peruvian Amazon, is a body of water that receives tailings and waste containing mercury (Hg) discharged by artisanal, informal, and illegal gold mining. The ecotoxic effect of heavy metals in surface water and sediments of the Madre de Dios River was evaluated on the microcrustacean Daphnia magna and the fish Paracheirodon innesi, in surface water and sediments by determining the toxicity level with the Roig ecotoxic scale, based on at the median lethal concentration (LC₅₀) for D. magna and with the median effective concentration (EC₅₀) for the sublethal effect “strange swimming” of P. innesi. Four points were sampled in the dry season in 2019 between the area of the crossing with the tributary Colorado River and the port of the Boca Colorado district, in Madre de Dios. Heavy metals were determined in water and sediment, additionally evaluating the pH and electrical conductivity. At the four sampling points, the Hg in surface water and sediments did not exceed the Peruvian Environmental Quality Standard for water from jungle rivers-Conservation of the aquatic environment (<0.0001 mg L^-1). LC₅₀ values in water and sediment in D. magna were non-toxic. The point with the highest toxicity for mortality and strange swimming in P. innesi in water was between the mining area and the port of Boca Colorado and it is considered slightly toxic. An analysis of acute and chronic ecotoxicological effects in Amazon aquatic planktonic, benthic and nektonic organisms is suggested.