Physiological response of Palaemon elegans to multi-anthropogenic stressors: assessing the impact of marine heatwaves and UV filters contained in sunscreens

Abstract

Sunscreens UV filters have been identified as emerging pollutants, representing a toxic threat to aquatic environments. In addition to that, regions with intense sunscreen usage are usually exposed to marine heat waves. This study shows the combined effects of high-water temperatures associated with sunscreen exposure in Palaemon elegans (Rathke, 1836). A full factorial experiment tested two temperature conditions (20 and 32 °C) and two sunscreens (one eco-friendly and the other non-eco-friendly) over 12 h. Shrimp were exposed to both stressors and sampled after 30 min (T1), 6 h (T6) and 12 h (T12). At each sampling point, metabolic biomarkers (cytochrome c oxidase, electron transport system) and oxidative stress biomarkers (glutathione-S-transferase, superoxide dismutase, lipid peroxidation) were analysed in the muscle and hepatopancreas. In the muscle, metabolic biomarkers showed that at T12, ETS activity was upregulated, showing a high metabolic demand at elevated temperatures, 32 °C. Meanwhile, COX activity was downregulated, suggesting possible mitochondrial dysfunction due to the increased accumulation of reactive oxygen species (ROS), further enhanced by exposure to chemicals present in the non-eco-friendly sunscreen. LPO activity indicated the presence of oxidative stress in organisms exposed to high temperatures, 32 °C, in combination with the non-eco-friendly sunscreen. In contrast, oxidative stress biomarkers such as GST and SOD showed that these antioxidant defences function effectively at 20 °C, but their efficacy fails at 32 °C, probably due to significant ROS accumulation associated with elevated temperatures and chemical pollutants. UV filters accumulation over time and temperature was analysed using UHPLC. Results show that the concentration (μg/g) of UV filters contained in the eco-friendly and non-eco.friendly sunscreens increased over time under higher temperature (32 °C). This indicates that marine heat waves can enhance the uptake of certain chemicals over just 12 h of exposure.