Polychaetes are known to be good bioindicators of marine pollution, such as inorganic contamination. Major and trace elements are commonly present in sediment and may be accumulated by polychaetes such as the tubiculous Diopatra neapolitana. In this study, D. neapolitana individuals were collected in the autumn, winter, spring, and summer of 2018/2019 from the Ria de Aveiro lagoon (western Portugal) to understand how seasonality influences element accumulation. The impact of the interaction of seasonality and elements on oxidative status, energy metabolism, and oxidative damage was also assessed. The obtained results showed that the activity of the antioxidant enzymes catalase, glutathione S-transferases, and non-protein thiol levels were higher in summer and that superoxide dismutase, lipid peroxidation, and electron transport system activity increased in winter. The lowest glycogen levels were observed during spring, and protein carbonylation was the highest during autumn. These results could mainly be related to high temperatures and the bioaccumulation of Al, As, Mn, and Zn. Energy-related parameters increased during spring and autumn, mainly due to the bioaccumulation of the same elements during spring and summer. Lipid damage was higher during winter, which was mainly due to salinity and temperature decreases. Overall, this study demonstrates that seasonality plays a role in element accumulation by polychaetes and that both impact the oxidative status of D. neapolitana.

Contamination with Arsenic, a toxic metalloid, is increasing in the marine environment. Additionally, global warming can alter metalloids toxicity. Polychaetes are key species in marine environments. By mobilizing sediments, they play vital roles in nutrient and element (including contaminants) cycles. Most studies with marine invertebrates focus on the effects of metalloids on either adults or larvae. Here, we bring information on the effects of temperature increase and arsenic contamination on the polychaete Hediste diversicolor in different growth stages and water temperatures. Feeding activity and biochemical responses—cholinesterase activity, indicators of cell damage, antioxidant and biotransformation enzymes and metabolic capacity—were evaluated. Temperature rise combined with As imposed alterations on feeding activity and biochemical endpoints at different growth stages. Small organisms have their antioxidant enzymes increased, avoiding lipid damage. However, larger organisms are the most affected class due to the inhibition of superoxide dismutase, which results in protein damage. Oxidative damage was observed on smaller and larger organisms exposed to As and temperature of 21 °C, demonstrating higher sensibility to the combination of temperature rise and As. The observed alterations may have ecological consequences, affecting the cycle of nutrients, sediment oxygenation and the food chain that depends on the bioturbation of this polychaete.

Contamination with Arsenic, a toxic metalloid, is increasing in the marine environment. Additionally, global warming can alter metalloids toxicity. Polychaetes are key species in marine environments. By mobilizing sediments, they play vital roles in nutrient and element (including contaminants) cycles. Most studies with marine invertebrates focused on the effects of metalloids on either adults or larvae. Here we bring information on the effects of temperature increase and arsenic contamination on the polychaete Hediste diversicolor in different growth stages and water temperatures. Feeding activity and biochemical responses – neurotransmission, indicators of cell damage, antioxidant and biotransformation enzymes and metabolic capacity - were evaluated. Temperature rise combined with As imposed alterations on feeding activity and biochemical endpoints at different growth stages. Small organisms have their antioxidant enzymes increased, avoiding lipid damage. However, larger organisms are the most affected class due to inhibition of superoxide dismutase, which resulted in protein damage. Oxidative damage was observed on smaller and larger organisms exposed to As and 21 °C, demonstrating higher sensibility to the combination of temperature rise and As. The observed alterations may have ecological consequences, affecting the cycle of nutrients, sediment oxygenation and the food chain that depend on the bioturbation of this polychaete.

Coastal ecosystems are increasingly threatened by climate change, especially the rising frequency of marine heatwaves (MHWs), which often co-occur with emerging nanomaterials such as graphene oxide (GO), whose ecological risks are still being evaluated. While the effects of GO have been studied in isolation, little is known about its interaction with thermal stress events. This research studied the combined effects of temperature (18 °C and 23 °C, simulating control and MHW conditions) and GO nanosheets exposure (0.01 mg/L) on two key estuarine bivalves: the clam Scrobicularia plana and the mussel Mytilus galloprovincialis. After 7 days of exposure (duration of many MHWs), energy metabolism, antioxidant defenses, oxidative damage, and neurotransmission were assessed. The results revealed that clams exhibited lower ETS and SOD activity when exposed to MHWs and lower SOD and AChE activities at MHW + GO, compared to the control treatment. Mussels relied primarily on SOD activity across treatments but showed increased susceptibility to GO nanosheets, with higher LPO levels and a significant reduction in AChE activity when exposed to GO at both temperatures. Overall, our findings suggest that S. plana shows a stronger response to the environmental alterations tested than M. galloprovincialis. Combined exposure to GO + MHW triggers species-specific biochemical responses in estuarine bivalves, highlighting how physiological traits shape the assessment of ecological risks posed by nanomaterial pollution under climate change.

Bisphenol A (BPA) and lithium (Li) are emerging contaminants widely detected in aquatic environments, yet their effects on regenerative processes remain poorly understood. This study evaluated the effects of BPA, Li, and their mixture on the regenerative capacity of the estuarine polychaete Hediste diversicolor, an important bioturbator in coastal ecosystems. Organisms were exposed for 21 days to BPA (0–135 μg/kg), Li (0–78.13 mg/kg), and BPA + Li mixtures under controlled laboratory conditions. Regeneration was assessed by determining the number of regenerated segments and the percentage of body width following posterior amputation. Results showed that BPA reduced regenerative capacity across all treatments, with the strongest effects observed at 5 and 45 μg/kg. Li exposure also decreased regeneration, particularly at 12.5 mg/kg. Combined exposure also resulted in reduced regenerative capacity, with the strongest effect observed at 12.5 mg/kg Li + 45 μg/kg BPA. Regeneration in mixture-exposed organisms was generally comparable to that observed following individual exposures. Notably, organisms exposed to 12.5 mg/kg Li and 5 μg/kg BPA individually had lower regenerative capacity than the corresponding mixture treatment, suggesting that co-exposure did not exacerbate the effects observed under individual exposures. Overall, BPA and Li negatively affect regeneration in H. diversicolor, highlighting regeneration as a sensitive endpoint for ecotoxicological assessment.