Assessing spinel zinc ferrite nanoparticles in aquatic ecosystems: Toxic threat or beneficial detoxifier for aquatic life?

•Evaluated the toxicity of zinc ferrite nanoparticles (ZnFe2O4−MNPs) on Mytilus galloprovincialis.•Co-exposure to ZnFe2O4−MNPs and TMX exacerbated oxidative stress and cellular damage.•Significant alterations in oxidative stress markers (SOD and MDA) observed.•Urges removal of nanoparticles post-treatment to prevent ecological harm. The effectiveness of magnetic nanoparticles in removing pollutants during water treatment is well established, but their introduction into aquatic ecosystems raises significant toxicity concerns. This study investigates the histological and physiological effects of zinc ferrite magnetic nanoparticles (ZnFe2O4−MNPs) on the Mediterranean mussel (Mytilus galloprovincialis) and examines the impact of concurrent exposure to these nanoparticles and the insecticide thiomethoxam (TMX). Mussels were exposed to nominal concentrations of ZnFe2O4−MNPs (1, 10, 100 mg/L) both individually and with TMX. Physiological assessments included measuring antioxidant enzyme levels (superoxide dismutase, catalase, glutathione S-transferase) and oxidative stress markers (malondialdehyde). Results showed that ZnFe2O4−MNPs increased antioxidant activity but also caused dose-dependent pathological changes. In contrast, combined exposure with TMX significantly (p < 0.05) reduced antioxidant defenses, indicated by lower superoxide dismutase (SOD) levels and higher malondialdehyde (MDA) concentrations, suggesting oxidative stress and potential cellular damage. These findings highlight the need for comprehensive toxicity assessments of nanoparticles in aquatic environments and advocate for their complete removal from water sources post-treatment. Further research is crucial to define the toxicity profiles of spinel ferrites to ensure their safe application in environmental remediation. [Display omitted]