The fish embryotoxicity test (FET) in zebrafish was used to identify toxicological hotspots along the Atoyac River, Mexico, to determine the presence of chemical substances with teratogenic effects for a possible monitoring program. Surface water samples were taken from eight stations along the river. We measured 18 physicochemical parameters and toxicity was determined through lethal dilution 50 (LDil50) test for each station. Further dilutions were made for malformations evaluation; delayed development and heartbeat frequency were registered as well. Multivariate cluster analysis was applied to characterize pollution sources and environmental quality. Two groups of stations were distinguished based on malformations lethality, which correspond to cluster analysis; COD and phosphate levels were close related. Malformations were obtained with all the samples and all dilutions, ranging from 1: 900 to 1: 66,000 and heartbeat frequency diminished with the dose. Even though the toxic effects were reduced with the river movement, lethality and teratogenicity were high in all stations, demonstrating a potential risk along the whole zone, where the river provides for agriculture and other human activities. Adoption of FET will provide an easy methodology for monitoring the efforts to reduce the pollution in the Atoyac River which is considered the most polluted river in Mexico.
Omar Arellano-Aguilar, Soledad Solis-Angeles, Luis Serrano-García, Eduardo Morales-Sierra, Alejandra Mendez-Serrano and Regina Montero-Montoya