The synergistic effects of chronic gas condensate pollution and warming on the survival, performance and reproduction of the mussel Brachidontes pharaonis

The increasing prevalence of multiple environmental stressors in marine ecosystems necessitates understanding their interactive effects. We investigated the individual and combined effects of chronic gas condensate exposure and warming of 3.1 °C on the survival, respiration and clearance rates of the mussel Brachidontes pharaonis and the mono/polycyclic aromatic hydrocarbons (M/PAHs) bioconcentration patterns in the mussels’ tissues. Mussels were exposed to gas condensate (0, 0.5, 5, 30, and 100 ppb) under both ambient and warmed conditions for 77 days. Mortality was negligible, while gas condensate exposure significantly and negatively affected metabolic rates. The combined effect of gas condensate and warming led to synergistic impacts on respiration rates. M/PAH bioconcentrations varied, showing a complex interaction between temperature and pollutant exposure. Mussels exposed to 100 ppb accumulated benzo[a]pyrene (BaP) at levels reaching 1215 ng/g — exceeding the regional regulatory threshold by a factor of 208. Our findings highlight the vulnerability of marine ecosystems to the combined threats of hydrocarbon pollution and climate change, emphasizing the need for further research on the long-term consequences of gas condensate exposure in a warmed environment. We further recommend implementing climate-based regulations to establish seasonal pollution thresholds.