The use of rare earth elements (REEs) has been increasing and one of the most used is neodymium (Nd). Being an emergent contaminant, its negative impacts are poorly understood. Aquatic organisms are also threatened by climate change-related factors, as is the case of warming, which can change the effects of REEs. Thus, the impacts of Nd, warming, and the combination of both stressors were studied in adult mussels and sperm of the species Mytilus galloprovincialis, after an exposure period of 28 days (adults) and 30 min (sperm). The effects were evaluated through the analysis of biochemical and histopathological alterations in adults and biochemical and physiological responses given by sperm. The results showed that mussels only activated their biotransformation capacity when exposed to the stressors acting alone, which was insufficient to avoid lipid peroxidation. Furthermore, warming (alone and combined with Nd) also produces damage to proteins. The digestive gland was the most sensitive organ to Nd, presenting several histopathological alterations. In the case of sperm, all stressors induced lipid peroxidation, a higher oxygen demand, and a decrease in velocity, even if the sperm viability was maintained. It seems that warming influenced the effects of Nd to some extent. The present findings contribute significantly to the field of REEs environmental toxicology by offering valuable insights into the impacts of Nd on various biological levels of mussels. Additionally, within the context of climate change, this study sheds light on how temperature influences the effects of Nd. The obtained results indicate that both stressors can potentially compromise the overall health of mussel populations, thereby affecting other species reliant on them for food and habitat. Moreover, this study highlights impaired sperm health, which could adversely affect their reproductive capacity and ultimately lead to population decline.

Per- and polyfluoroalkyl substances (PFAS) are persistent pollutants with rising concern due to their stability and toxicity. The production of novel PFAS with shorter carbon chains in the environment raises concerns related to their stability and their potential toxicity in organisms. This study examines the effects of hexafluoropropylene oxide dimer acid ammonium (HFPO-DA, or GenX) on the marine mussel Mytilus galloprovincialis under different salinity conditions. Mussels were exposed to environmentally relevant HFPO-DA concentrations, and multiple biomarkers were assessed: these include oxidative stress responses and damages, as well as neurotoxicity and histological damages. Results show that salinity strongly modulates toxicity: hyposaline conditions activated robust antioxidant defenses and increased respiration, while intermediate and high salinities led to greater metabolic disruption and cellular damage. At the highest concentration of HFPO-DA at intermediate salinities, mussels favored non-enzymatic antioxidant responses over enzymatic activity. These findings reveal a complex interplay between salinity and PFAS toxicity and underscore the need to integrate environmental variability into ecotoxicological risk assessments. Therefore, both climate change and PFAS pollution in estuarine ecosystems require urgent, context-sensitive mitigation strategies.

The growing use of products containing rare earth elements (REEs) may lead to higher environmental emissions of these elements, which can potentially enter aquatic systems. Praseodymium (Pr) and europium (Eu) are widely used REEs with various applications. However, their ecotoxicological impacts remain largely unexplored, with poorly understood risks to wildlife. Moreover, organisms also face environmental stressors like salinity fluctuations, and the nature of the interaction between salinity variations and contaminants is not yet clear. Therefore, this study aimed to evaluate the influence of salinity shifts on the impacts of Pr and Eu on adult mussels and the sperm of the species Mytilus galloprovincialis after 28 days and 30 min of exposure, respectively. To do so, biochemical and histopathological alterations were evaluated in adults, while biochemical and physiological changes were analysed in sperm. Additionally, the Integrated Biological Index (IBR) was calculated to understand the overall impact of each treatment. The results showed that adult mussels were most affected when exposed to the combination of high salinity and each element, which altered the behaviour of defence mechanisms causing redox imbalance and cellular damage. On the other hand, sperm demonstrated sensitivity to specific REE-salinity combinations, particularly Pr at lower salinity and Eu at higher salinity. These specific treatments elicited changes in sperm motility and velocity: Pr 20 led to a higher production of O₂⁻ and a decrease in velocity, while Eu 40 resulted in reduced motility and an increase in irregular movement. At both lower and higher salinity levels, exposure to Eu caused similar sensitivities in adults and sperm, reflected by comparable IBR scores. In contrast, Pr exposure induced greater alterations in sperm than in adult mussels at lower salinity, whereas the reverse was observed at higher salinity. These findings suggest that reproductive success and population dynamics could be modulated by interactions between salinity levels and REE pollution, highlighting the need for further investigation into how REEs and environmental factors interact. This study offers valuable insights to inform policymakers about the potential risks of REE contamination, emphasising the importance of implementing environmental regulations and developing strategies to mitigate the impact of these pollutants.

Climate-induced ocean warming poses a major threat to marine invertebrate reproduction, including the sea urchin Paracentrotus lividus, a species of considerable ecological, economic, and scientific interest. Its gonads, highly valued as a culinary delicacy, support local fisheries and aquaculture industries, making reproductive health a critical factor for both conservation and commercial viability. The present study reported the effects of elevated seawater temperatures, mimicking marine heatwave (MHW) conditions, on gonadal maturation and fertilization success on P. lividus. Here, adult specimens at the mature stage of gametogenesis were exposed to control (18 °C) and elevated temperature regimes (24 °C) over a six-week period, and key reproductive metrics were assessed, including histological analysis. Morphological analysis showed very evident gonadal retraction, nearly devoid of germ cells, both for males and females, with a significant decrease in the gonadal index. In addition, histological analysis revealed consistent damage to the gonads, with a significantly increase in histopathological index in specimens kept at 24 °C. These findings reinforce the temperature sensitivity of P. lividus reproduction, suggesting that recurrent heatwaves could severely impair its reproductive output and population dynamics with potential cascading effects on benthic community structure in a long-term ocean warming predicted to intensify.

Air pollution is a major environmental and public health issue, largely driven by human activities. The present study evaluates the combined use of two bioindicators from different taxonomic groups, the moss Rhytidiadelphus squarrosus and the terrestrial snail Cornu aspersum, to assess early biological effects induced by atmospheric exposure to toxic elements. Both species, chosen for their sensitivity, simple physiology, and suitability for field transplantation, were exposed for 30 days at two sites in southern Italy with contrasting environmental conditions. Toxic element accumulation in moss biomass and snail tissues was measured using ICP-OES, while snail shell composition was analyzed using FTIR spectroscopy. Biological responses were assessed through oxidative stress biomarkers (ROS levels and catalase activity), HSP70 expression determined by Western blotting, and structural damage, including ultrastructural changes in mosses and histopathological alterations in snails. Results showed site-dependent patterns of toxic elements accumulation in both organisms, consistent with increased oxidative stress and induction of HSP70 expression. Enlargement of the albumen gland and histological alterations in digestive tubules and reproductive systems were found in snails. Mosses showed severe ultrastructural alterations. FTIR analysis revealed changes in snail shell composition consistent with metal exposure. Principal component analysis highlighted clear patterns linking contamination, oxidative stress, and structural damage, supporting the complementarity of the two bioindicators and their ability to capture distinct exposure pathways and biological effects.