Estuary of the Danube

Abstract

The Danube is the second largest major European river, with a huge estuary located in two countries: Ukraine and Romania. The Danube watershed embraces 15 highly industrialized European countries that produce a high level of anthropogenic pressure. During the last 30 years they have influenced the river, estuary, and Black Sea. At present the Danube runoff is totally regulated by dams. This factor changed the hydrological regime. Another factor that has changed the hydrochemical regime is the oversupply of nutrients, primarily nitrogen and phosphorus. This affected the environment of the river, estuary, and northwestern shelf of the Black Sea. Eutrophication, “water blooming”, and near-bottom hypoxia as a result of this process are developing in the northwestern part of the Black Sea. In the estuary, both water quality and bottom sediments have deteriorated, and the fish catch and biodiversity have decreased. At present a new source of eutrophication is bottom sediment in the shore zone of the sea.