Elevated water temperatures enhance 2,4,6-trinitrotoluene induced stress response of carbonyl reductase in blue mussels (Mytilus spp.) – another environmental impact of climate change?

Toxic explosives leaking from submerged munitions appear as an emerging marine pollutant in recent years. The nitroaromatic compound 2,4,6-trinitrotoluene (TNT) is of particular interest in this context. TNT poses a threat to marine environments and organisms. Previous studies showed that TNT and its metabolites are incorporated in mussel tissue thereby causing adverse effects through cellular oxidative stress. Recently, the impact of TNT on mRNA expression of the enzyme carbonyl reductase (CR) in blue mussels was discovered. This enzyme plays a key part in the cellular antioxidative system. A factor that should been taken into account is the increase in water temperature caused by anthropogenic climate change. To investigate potential synergistic effects of TNT in combination with elevated water temperatures on CR expression, blue mussels were exposed to concentrations of 0.1 µg/L, 50 µg/L, and 500 µg/L TNT and water temperatures of 11°C, 15°C and 18°C, respectively, in the present study. Semiquantitative PCR analysis of CR mRNA expression in different tissues confirmed that TNT leads to increased mRNA expression levels, especially in gill tissue even at lower concentrations as tested in previous studies. Furthermore, varying water temperatures apparently influenced CR gene expression. Our study suggests a higher vulnerability to xenobiotic-induced oxidative stress in case of simultaneous presence of pollution from munitions and elevated water temperature. Our findings also underline the importance of molecular biomarkers like CR as a method for assessment of the impact of environmental stressors on the marine ecosphere.