Embryotoxicity Produced by Contaminated Sediment and Pore Water in Zebrafish (danio rerio). A Case Study at Madín Dam

Sediments are an important environmental matrix, considered as the fingerprint of water bodies, since they can incorporate pollutants that remain there for long periods of time. The Madin Dam is an important reservoir in Mexico and several studies have shown that the water of this reservoir is severely impacted by contamination, particularly by heavy metals, which endangers the health of hydrobionts and users of the resource. Thus, the objective of this study was to evaluate the embryotoxicity produced by the exposure of sediments and pore water from Madin Dam on Danio rerio. Sampling was conducted at four points in Madín Dam, analyzing the physicochemical properties of sediments and metal concentrations such as Al, Fe, Pb, Hg, and Cd. From these, the Contamination Factor (CF), Enrichment Factor (EF), and modified Contamination Degree (mCdeg) were calculated. Subsequently, zebrafish embryos were exposed to sediments and pore water, and median lethal concentrations (LC₅₀) were calculated. Finally, developmental alterations were assessed using the General Morphological Score (GMS), hatching rate and teratogenic effects at sublethal concentrations. Sediments caused higher mortality compared to pore water at all sampling points. Sediments near the tributaries of the San Juan and Tlanepantla rivers showed a higher percentage of damage, suggesting a deterioration in sediment quality due to contaminants washed in from these areas. According to the GMS, a similarity in developmental delay was observed in embryos exposed to sediments and pore water as well as pericardial edema and scoliosis, with a more pronounced effect in sediments from the Nuevo Madín location. The metal concentration order in sediments was Fe > Al > Pb > Cd > Hg, highlighting the importance of Pb, Cd, Fe and Al due to their contamination level. These findings emphasize the need for effective monitoring and addressing of pollution sources in Madín Dam sediments. This approach is crucial to safeguard environmental health of the reservoir and implement proactive measures aimed at mitigating associated negative impacts.