Combined Climate and Chemical Stressors: How Spatial Variability Shapes the Response of Ficopomatus enigmaticus (Fauvel, 1923) to Dimethyl Sulfoxide (DMSO) and Heatwaves, and What It Means for Ecotoxicology.

Ficopomatus enigmaticus, a reef-forming serpulid, has emerged as a promising candidate for biomonitoring and ecotoxicology studies. Recent research has focused on adult stress responses, highlighting the need to understand population-specific responses. This study employed a multi-biomarker approach to investigate how F. enigmaticus adults from two populations in the NE Adriatic (Site A) and NE Tyrrhenian (Site B) responded to chronic exposure to heat and chemical stress (dimethyl sulfoxide, DMSO), individually and in combination. The analysis detected significant differences in protein content and the activities of superoxide dismutase (SOD) and glutathione S-transferase (GST) between populations. Notably, no oxidative damage (measured as lipid peroxidation, LPO) was detected in any population or treatment. Similarly, no significant differences were detected in the integrated biomarker response index (IBRv2i). However, lower IBRv2i values at Site A suggested reduced stress conditions, possibly indicating that this site may have lower baseline stress. Overall, treatment effects were limited and site-specific: only the combined heat and DMSO exposure at Site A lowered GST activity compared to heat stress alone. Nevertheless, both populations exhibited broadly similar biochemical response patterns to stress. Our findings deepen the understanding of stress physiology in F. enigmaticus, underscoring the ecological importance of multi-stressor approaches in environmental monitoring.