State of the Marine Environment along the Bulgarian Black Sea Coast as Indicated by Acetylcholinesterase Activity of Wedge Clam (Donax trunculus Linnaeus, 1758)

The aim of the study was to assess changes in the acetylcholinesterase (AChE) activity in the wedge clam (Donax trunculus L.), gathered in spring (March), summer (June/July) and early autumn (September) from shallow sublittoral sandy habitats at different localities along the Bulgarian Black Sea coast. It is well established that inhibition of AChE in marine organisms is mainly caused by the neurotoxic effects of organophosphate and carbamate pesticides, however recently it was found that a number of other chemical substances have similar effects including heavy metals, polycyclic aromatic hydrocarbons, detergents etc. The activity of AChE in the soft body of the clams in our study showed considerable variation among the studied localities. The most significant AChE inhibition was present in clams from localities close to coastal areas with intensive tourism, such as the big resorts Slanchev Bryag, Duni, Arkutino and Primorsko. Significant seasonal differences in AChE activity were also established. Higher activity of AChE was present in the wedge clams gathered in autumn than in the other seasons. Overall, our results demonstrated for the first time the presence of significant ecotoxicological effects of anthropogenic impact on the shallow sublittoral sandy habitats along the Bulgarian Black Sea coast where D. trunculus is a dominant. Hence, this clam species appears to be suitable bioindicator of marine environmental quality.