An integrated chemical and biomarker approach using Ucides cordatus (Crustacea; Decapoda) to assess trace element contamination and its biological impacts across two Amazonian estuaries

In this study, an integrated chemical and biomarker approach was applied using the mangrove crab Ucides cordatus to assess trace element contamination and its biological impacts across two distinct Amazonian estuaries. Crabs were collected from São José Bay (A1—minimally impacted) and São Marcos Bay (A2—impacted by port activities) on the Amazon coast of Brazil. Simultaneously with crab sampling, physicochemical parameters and trace element levels in sediment and water samples were assessed. Biometric measurements included cephalothorax length and width, cheliped propodus length and width, movable finger length and width, and total weight. Two biomarkers, genotoxic responses (micronuclei) and histopathological lesions (gills and liver hepatopancreas), were measured. Abiotic parameters, such as pH, dissolved oxygen, and salinity, were similar between the two study areas (A1 and A2). However, the concentrations of trace elements (Zn, Fe, Al, and Mn) in the water were increased in A2. Biometric data revealed that crabs from A2 were significantly smaller and lighter ( p < 0.05) than those from A1. Gill lesions (marginal canal deformation, pillar cell rupture, and necrosis) were frequently observed in crabs from both sites, with a higher prevalence in A2. Hepatopancreas histological alterations (e.g., necrosis) were significantly more common in crabs from A2 ( p < 0.05). Genotoxic responses, such as pycnotic nuclei, were also significantly more frequent in A2 ( p < 0.05). The results demonstrate that Ucides cordatus effectively reflects environmental contamination through measurable histological and genotoxic biomarkers, which is consistent with the chemical evidence of trace element pollution in estuarine environments.