Stress Ecology of Wedge Clams Donax trunculus Linnaeus, 1758 from Sandy Habitats of the Bulgarian Black Sea Coast

The aim of the present study was to assess the multiple stress or effects and adaptive capacity of wedge clams Donax trunculus Linnaeus, 1758 from nine typical localities of the Bulgarian Black Sea coast. The accumulation of trace metals, polycyclic aromatic hydrocarbons (PAH), microbiome composition and contents of microplastic particles were analysed. The levels of lipid peroxidation (LPO), protein oxidation (PO), glutathione (GSH) and activity of glutathione-S-transferase (GST) and acetylcholine esterase (AChE) in wedge clams were measured. The relationships among environmental stressor variables and values of oxidative stress biomarkers were analysed by Cluster and Principal Components Analysis. The results showed that the induction of LPO and activation of GST were associated with levels of metal accumulation in wedge clams' tissues. PO was more strongly related to increased levels of PAH, while activity of AChE was associated with the abundance of microorganism species present in the wedge clams. In conclusion, we demonstrated the presence of specific stress response of the wedge clams to the state variables of the marine environment of their habitats. Within their tolerance range, the wedge clams were able to manage and effectively compensate the different pressures of multiple environmental stressors in their local habitats.