Toxicological impacts of biogenic zinc oxide nanoparticles on blue Parrotfish using multibiomarker assessment

This research demonstrates how using Padina pavonica extract to create zinc oxide nanoparticles (ZnO-NPs) can be toxic to aquatic organisms. Blue Parrotfish (Scarus coeruleus) were used to evaluate the effects of ZnO-NPs over a 15-day period at different concentration levels (0–80 mg/L). The mortality rate was closely related to the concentrations tested; therefore, at 80 mg/L, every single fish died from exposure. The indication of oxidative stress through the decrease of glutathione (GSH) levels, and a nonlinear relationship of the reactive oxygen species (ROS) suggests cellular adaptation occurred during this time. As expected, there was also an overall decrease in activity of hepatic enzymes (ALT, AST, ALP) due to damage done to the liver; this was supported further through the tissue analysis by histopathology assessment. Additionally, the ionic homeostasis is disrupted by increased tissue levels of sodium (Na+), potassium (K+), and calcium (Ca²+). At sublethal levels, ZnO-NPs also inhibited bacterial growth (Streptococcus and Vibrio), demonstrating both toxic and antibacterial properties These findings highlight the ecological risks associated with nanoparticle-driven marine pollution and emphasize the need to establish environmentally safe exposure limits to protect coastal and marine ecosystems.