Resumen:
The Ecuadorian Amazon has experienced a significant land use change due to the demographic increase and the
expansion of the agricultural frontier. Such changes in land use have been associated to water pollution prob lems, including the emission of untreated urban wastewater and pesticides. Here we provide the first report on
the influence of urbanization and intensive agriculture expansion on water quality parameters, pesticide
contamination and the ecological status of Amazonian freshwater ecosystems of Ecuador. We monitored 19
water quality parameters, 27 pesticides, and the macroinvertebrate community in 40 sampling locations of the
Napo River basin (northern Ecuador), including a nature conservation reserve and sites in areas influenced by
African palm oil production, corn production and urbanization. The ecological risks of pesticides were assessed
using a probabilistic approach based on species sensitivity distributions. The results of our study show that urban
areas and areas dominated by African palm oil production have a significant influence on water quality pa rameters, affecting macroinvertebrate communities and biomonitoring indices. Pesticide residues were detected
in all sampling sites, with carbendazim, azoxystrobin, diazinon, propiconazole and imidacloprid showing the
largest prevalence (>80% of the samples). We found a significant effect of land use on water pesticide
contamination, with residues of organophosphate insecticides correlating with African palm oil production and
some fungicides with urban areas. The pesticide risk assessment indicated organophosphate insecticides (ethion,
chlorpyrifos, azinphos-methyl, profenofos and prothiophos) and imidacloprid as the compounds posing the
