Based on published and unpublished data, the information about habitat and biological diversity in the sea is systematized. Relations of species, populations and communities with ther marine environment are illustrated by numerous examples. Special attention is drawn to the aquatic birds, which are among the less investigated elements of marine ecosystem. Consequences of diverse human activities in the sea and in the drainage basin to marine ecosystem are analysed and possible ways of protection are discussed. The text is illustrated by colour pictures and photographs. Besides tables and figures, there is a list of References, Glossary of special terms and a Chronological list of major events and contributions to the Black Sea ecology
