RESUMO
Oreochromis niloticus was used to determine the effects of heavy metals and their concentration in aquatic environments. Its wide distribution, resistance, and economical importance make it a suitable biomonitor. The present study was conducted in the Tenango Dam (Puebla, Mexico) to determine water quality and its impact on O. niloticus, a species that is cultured and commercialized in this area. Five samples were collected over 1 year to evaluate the water's physicochemical parameters (temperature, dissolved oxygen, pH, and hardness) and metal contents (cadmium, chromium, copper, and lead). Metal concentrations, bioconcentration factors, and metallothionein levels were also assessed in O. niloticus livers and muscle tissues. Water and tilapia quality were estimated according to current Mexican guidelines. Results indicated that the water's physicochemical parameters were within acceptable ranges. Metal concentrations, however, suggested that this resource was not suitable for urban use. Moreover, metal levels in fish tissues exceeded the acceptable limits during two periods, rendering it unsuitable for human consumption. The bioconcentration factor indicated that the metals can potentially accumulate in organisms. Furthermore, metallothionein levels in liver and muscle showed a direct correlation with metal concentrations in these tissues. This is the first study to use tilapia as an indicator of contamination in the Tenango Dam, and also the first to describe the presence of metals in this water body.