Interactive effects of Titanium-based compounds with Gadolinium and Mercury in Mytilus galloprovincialis

The combined toxicity of metals in aquatic environments is a critical concern due to the complex interactions between different metal contaminants, as well as their interactions with other environmental factors. These combined effects often result in synergistic, antagonistic, or additive toxic responses, leading to heightened risks for aquatic organisms and ecosystems. This study investigates the toxicity of titanium in its bulk form (Ti) and as nanoparticles (nTi) when combined with other elements like gadolinium (Gd) and mercury (Hg), focusing on their effects on the mussel Mytilus galloprovincialis. Mussels were exposed to Ti or nTi alone, or their combination with Gd or Hg. Biomarkers of metabolic capacity and oxidative stress were measured to assess the impacts on the organisms. The results showed that exposure to Ti and nTi alone did not significantly disrupt the mussels' metabolic capacity, energy reserves or antioxidant defense systems, indicating that these concentrations were below the toxicity threshold. However, when mussels were exposed to Gd and Hg, in combination with Ti or nTi, the metabolism increased, the detoxification enzyme rose, the redox homeostasis was disrupted, leading to cellular damage. The integrated biomarker index showed that mussels were more responsive to the combination of Ti/nTi+Hg, highlighting the elevated toxicity of co-exposure to Ti and Hg. These findings suggest that while Ti-based materials may not pose significant oxidative stress on their own, their interaction with more toxic elements like Gd and Hg exacerbates the organisms' metabolic burden, compromising their health. This study emphasizes the importance of considering pollutant mixtures in assessing the environmental impacts of emerging and traditional contaminants.