黑料网

Abstract

The Black Sea is characterized by its large continental shelf, water stratification, lack of vertical mixing, highest H2S content of deep waters worldwide, strong freshwater input, increased levels of nutrients and detritus, weak water mass exchange with the Mediterranean Sea, large spatial and temporal variability of physical and chemical properties, about half salinities of those noticed in the World?s Ocean, slightly different composition of the ionic ratios. Poorer flora and fauna have been previously compensated by their high biological productivity. Relatively few alien species entered this particular environment. Up to the end of the fifth decade of the 20th century the Black Sea underwent major changes which contributed to a severe ecological disequilibrium. Considerable efforts have been devoted after 1990 for the rehabilitation of the still highly endangered sea. Within these joint contemporary concerns the continuous development of Romanian oceanography has enriched Black Sea research. Black Sea biodiversity studies have shown that since 1950-1960 there have been significant changes in the ecosystem as a whole regarding populations, species composition and biocenosis. These changes put an end to centuries of relatively stable ecological balances and mark the beginning of a new era in Black Sea biodiversity, affecting plants, animals, benthic and pelagic inhabitants, mass and rare species, and commercially exploited organisms. The different taxa in the Black Sea have not been studied to the same extent in each of the littoral states, However, the reliable data that exist are already sufficient to draw conclusions about the present state of the Black Sea biota, including the main reasons for the changes that have occurred, the regions of the sea that have been subject to varying degrees of anthropogenic transformation, endangered species, populations and communities, and major gaps in our knowledge of biological diversity. The major biological long-term changes during the last 30 year could be summarized as follows:

Biography