Biomarkers of DNA damage in common carp inhabiting an agriculturally impacted lake in Mexico

Aquatic organisms constituted an important food resource for human populations. These are primarily obtained through capture fisheries and aquaculture. However, aquatic ecosystems are increasingly affected by complex mixtures of legacy and emerging contaminants derived from agricultural and urban activities. Many of these compounds are persistent and readily dispersed in aquatic environments, contributing to the deterioration of surface water quality and potentially inducing genotoxic effects in aquatic organisms, which may also represent a risk to consumers. The objective of this study was to determine DNA damage in Cyprinus carpio from Atlangatepec Lagoon, Tlaxcala, Mexico, an area characterised by fish production and strong influence from agricultural activities. Blood samples (100 µL) were collected from nine adult organisms in the study area and from organisms obtained from aquaculture production units, which served as the control group. Samples were processed according to the standard alkaline comet assay protocol. Slides were analysed under a fluorescence microscope using Comet Assay IV software. A total of 100 nucleoids per slide (two slides per individual) were analysed to assess tail length, tail intensity, and tail moment parameters as genotoxicity biomarkers. Before statistical analysis, data were log10- and arcsine-transformed to stabilise variances and verify statistical assumptions. Differences between groups were analysed using Welch’s t-test in R software (v.4.4.2). Significant differences (p < 0.05) were observed between fish from Atlangatepec Lake and the control group for all evaluated parameters, indicating increased DNA damage in exposed organisms. The results indicate the presence of genotoxic agents, likely associated with agricultural runoff and urban discharges. Likewise, these findings confirm the effectiveness of the comet assay as a sensitive biomonitoring tool in ecotoxicology and its value for environmental genotoxicity assessment in aquatic ecosystems of fisheries importance.