Ecotoxicological Risk of Sediments from the Salado River Using Earthworms (Eisenia sp.)

Introduction

The Salado River is located in the Mezquital Valley, Mexico. Along its course, it receives large volumes of wastewater from industrial, agricultural, and mining activities, as well as effluents originating from Mexico City through the Grand Drainage Canal. These discharges contain toxic substances that, due to their physicochemical properties, accumulate in river sediments, posing a potential risk to organisms inhabiting this ecosystem. The aim of this study was to evaluate the genotoxic effects of contaminants accumulated in the sediments on the coelomocytes of earthworms (Eisenia sp.) collected from the river.

Methods

Ten earthworms (Eisenia sp.) were collected from each of five sampling sites distributed along the Salado River. In the laboratory, the organisms were placed in an extrusion solution to obtain coelomocytes. Genotoxicity was assessed using the micronucleus and comet assays. Cell viability was determined by the trypan blue exclusion test, and cytotoxicity was evaluated using the neutral red uptake assay. Statistical analyses were performed by comparing each sampling site with a reference site and a negative control using analysis of variance (ANOVA) followed by Tukey's post hoc test, with a significance level of p < 0.05.

Results

Earthworms collected from the Salado River exhibited cell viability greater than 80%, with no evidence of cytotoxic effects among sampling sites. DNA damage was detected through a statistically significant increase (p < 0.05) in both micronucleus frequency and DNA fragmentation compared with the reference site and the negative control.

Conclusions

The results indicate the presence of compounds with genotoxic potential in the river sediments, representing a risk to aquatic and terrestrial biota and potentially affecting overall ecosystem health.