Ecotoxicology of Mercerized Cellulose-Treated Tannery Effluents Using Salvinia auriculata (Salviniaceae) as a Bioindicator.

Given the growing concern over the environmental impacts of industrial effluents, particularly from tanneries, assessing the ecotoxicological risks associated with these effluents, even after remediation treatments, is crucial. Therefore, we aimed to evaluate the potential effects of exposure to raw and treated tannery effluents with mercerized microcrystalline cellulose particles (MCPs) on Salvinia auriculata. This study addresses the need for sustainable treatment alternatives that can reduce toxicity while assessing the residual impacts on aquatic plants. Plants were exposed to effluent dilutions (0.3% and 3.1%) for 15 days under controlled conditions. Biomarkers related to growth, photosynthesis (chlorophyll a, b, and total), oxidative stress (ROS, MDA, nitrite), and antioxidant enzyme activities (SOD, CAT, and SOD/CAT ratio) were analyzed. Although MCPs reduced chromium concentrations, treated effluents still caused significant toxicity, with root growth inhibition reaching 40% and chlorophyll a decreasing by over 30%. Principal Component Analysis (PCA) and Cluster Analysis revealed clear group separation, driven by Cr accumulation and changes in key physiological and biochemical markers. These findings highlight the partial effectiveness of MCPs and the importance of including ecotoxicological endpoints when evaluating treatment technologies. Although MCPs represent a promising step toward environmentally friendly remediation, further optimization is needed to reduce residual toxicity and assess long-term and multispecies effects. The study also reinforces the utility of aquatic macrophytes as sentinel organisms in environmental monitoring and supports the development of more robust effluent management strategies that integrate both chemical and biological evaluations.