Present state and evolution trends of biodiversity in the Black Sea: decline and restoration

Abstract The biological diversity, including the marine one, and its advanced and continuous decline, respectively, range among priority issues at planetary level, y compris the Black Sea, nowadays. As to the Black Sea and its biodiversity, among the other concerns on present ecological disequilibrium, pollution, living resources, the problem consists of its five times larger watershed than the sea surface itself, totalizing about 350 km3 of freshwater, originating in the hydrographic basins of the Danube, Dneper, Dnester and Don, each year. The six Black Sea coastal states Bulgaria, Georgia, Romania, Russian Federation and Turkey themselves affect marine biodiversity directly through their land-based pollution sources. This review reveals the present state and evolution trends of Black Sea macrophytobenthos, zoobenthos, phytoplankton and related blooms, zooplankton, ichtyofauna and cetaceans, with some examples of changes occurring in the Romanian coastal and marine ecosystem during the last seven decades. The main conclusions highlight that the Black Sea ecosystem is different from that documented in the former reference periods, a slight improvement and rehabilitation tendency of the ecosystem since 1995, the considerable improvement of the pelagic ecosystem especially due to weakening of anthropic pressure. But it is still out of balance by its biodiversity and fish stocks due to eutrophication, overfishing and alien species invasion. The long lasting processes of ecosystem restoration, of qualitative improvement of environmental factors and of fishery resources depend on the efficiency of conservation, protection and management measures to be undertaken together by Danube riparian countries and Black Sea coastal states. There is still a strong need for continuing regional co-operation in the fields of monitoring, research and legislation, by developing scientifically sound data bases and communication networks, for decision makers and end-users.