Ultraviolet (UV) filters are present in a broad range of personal hygiene products, which may be transported via aquatic environments and domestic wastewaters due to inefficient treating station sewage removal and direct human contact. The aim of the present study was to evaluate the potential effects of a UV filter, in particular benzophenone-3 (BP3) (also known as oxybenzone) on the mussel species Mytilus galloprovincialis. Mussels were exposed to this organic substance for 96 h in environmentally relevant concentrations (10, 100, and 1000 ng/L). After exposure, biomarkers related with the mussels’ metabolism and oxidative stress were evaluated. The results revealed significantly higher activity of electron transport system and energy reserves (glycogen and protein (PROT)) at the intermediate concentration of 100 ng/L, suggesting that at lower concentrations mussels’ metabolism was not activated due to low stress. Conversely, at the highest concentration (1000 ng/L), mussels were no longer able to continue to increase their metabolic activity. Higher metabolic capacity was accompanied by increased PROT content associated with increased enzyme production to activate their antioxidant system. Nevertheless, at the highest concentration, cellular damage occurred as a consequence of ineffective activation of antioxidant and biotransformation enzymes. The results of the present study address uncertainties that are fundamental to the environmental risk assessment and management of these economically important near-shore bivalves and other marine species. Although an acute exposure was performed, alterations observed indicate the negative impacts of BP3 towards marine bivalves, which could be enhanced after longer exposure periods or if mussels are simultaneously exposed to other stressors (e.g., other pollutants or climate change related factors). The present study may thus contribute to the definition of fundamental knowledge for the establishment of appropriate regulatory guidelines and practices that ensure the preservation and sustainability of biological resources, allowing for prediction and mitigation of the impacts from these compounds.

Marine organisms are constantly exposed to multiple stressors including pollutants released into the environment, such as personal care products (PCPs), and climate change-derived factors, namely warming, which are aggravated by anthropogenic drivers and pose increasing pressure on coastal ecosystems. Avobenzone (AVO) is one of the most used ultraviolet (UV) filters in PCPs which have been increasingly used and, thereby, identified in aquatic environments. However, data regarding the influence of warming on the impacts caused by AVO in bivalves is lacking. Mussels are considered good bioindicators thus being often employed in ecotoxicology studies. Hence, the present study aimed to evaluate the toxic effects of an environmentally relevant concentration of AVO (0.5 μg/L) and warming (21 °C), acting alone or in combination, on sperm and adults of the Mediterranean mussel species Mytilus galloprovincialis, through in vitro and in vivo tests, respectively. AVO and warming effects were evaluated by assessing oxidative status, viability, genotoxicity, motility, and kinetics in sperm, together with the quantification of energy content, metabolic capacity, biological defence mechanisms, cellular damage, and neurotoxicity in adults. AVO induced genotoxicity and increased respiration rate in sperm while enhancing the biotransformation enzymes' activity in adults. Exposure to warming led to an increase in respiration rate, ROS overproduction, cellular damage, and viability decrease in sperm whereas metabolic capacity increased in adults. AVO combined with warming caused oxidative stress, cellular damage, genotoxicity, and decreased motility in sperm, while only antioxidant enzymes' activity was enhanced in adults. Overall, the present study demonstrated that when acting in combination the effects of both stressors were more prominent. Furthermore, considering the multiple-stressor scenario tested, major toxic effects occurred in male gametes in comparison to adults.

Marine coastal ecosystems face growing threats from chemical pollution and climate change, particularly through the intensification of marine heatwaves (MHWs). Critical metals, such as lithium (Li), cobalt (Co), and nickel (Ni), are increasingly detected in aquatic environments due to inadequate recycling and disposal practices. This study assessed the individual and combined effects of 100 µg/L of Li, Co, and Ni on the marine mussel Mytilus galloprovincialis under present-day temperature (17 °C) and simulated MHW conditions. Compared to 17 °C, under the MHW scenario, mussels exhibited enhanced mitochondrial activity and oxidative stress, particularly when exposed to the combination of the three elements. Temperature stress led to a decreased detoxification capacity, except in the case of Ni single exposure, which is consistent with the accumulation of elements in the mussels' soft tissues (with lower Ni accumulation under the MHW scenario but higher for Co and Li). The Integrated Biological Response (IBR) index increased from 8.3 to 13.6 under single-metal exposure to 18.1 and 13.9 in metal mixture treatments at 17 °C and MHW scenarios, respectively, highlighting the strong cumulative stress induced by combined metal exposure. For Co, higher IBR values were observed under MHW scenario, whereas for the remaining treatments, IBR values were similar (Li) or lower (Ni and Mix) under warming, indicating that higher temperatures imposed overwhelming conditions that limited the mussels' capacity to elicit an effective response. Together, these findings demonstrate that incorporating thermal anomalies and realistic contaminant mixtures into ecotoxicological risk assessments is therefore crucial to avoid underestimating the biological risks associated with metals from Li batteries. These insights highlight the need for urgent mitigation and circular economy strategies to reduce metal leakage into marine environments and protect ecosystem resilience in a rapidly warming ocean.