IS THE INVASION OF THE AZOV-BLACK SEA BASIN BY THE ARK CLAM ANADARA KAGOSHIMENSIS DANGEROUS?

The bivalve Anadara kagoshimensis (Tokunaga, 1906), a recent invader of the Azov-Black Sea basin, is classified as one of the most dangerous invasive species in Russia. The main objective of this research was to test the hypothesis about the difference in zoobenthos structure assessed by Shannon, Simpson, Pielou and Margalef ecological indices (otherwise – by indexed «outer contour» of macrozoobenthos condition) in the presence and absence of A. kagoshimensis. Additionally, the possibility of A. kagoshimensis to enter direct competitive relationships with some native species was considered. The obtained results indicate that the emergence of A. kagoshimensis as an invasive species near the Black Sea coast of Crimea did not result in a modification of the indexed ‘outer contour’ of the structural organisation of the native zoobenthos complex. At the same time, this ‘external’ stability was achieved against a background of internal restructuring of the benthic ecosystem, associated with natural changes in the degree of dominance of individual species. The mere presence of intrasystem changes in the presence of A. kagoshimensis does not prove the determining role of A. kagoshimensis itself in these intrasystem processes. The researchers have no sufficient evidence of direct competition between A. kagoshimensis and native species for substrate and food in areas where they share a habitat. More obvious may be a positive or negative correlation in the dynamics of the development of individual species, mediated by changes in the conditions of their habitat – climatic, edaphic and trophic. An example of this is the substitution (not direct replacement) of the psammophilic bivalve Chamelea gallina by the pelophilic A. kagoshimensis under conditions of biotope siltation. In light of the current state of knowledge regarding the results of the invasion of A. kagoshimensis into the Azov-Black Sea basin, it is not yet possible to conclude that the results are negative or dangerous, given the lack of sufficient evidence.