Long-term biological changes along Danube and Danube Delta systems after industrialization period

Abstract

Over the last 50 years humans have converted the export of fluvial materials which induced significant changes in biology, chemistry and morphology of the aquatic systems. The study presents the long-term changes induced on biotic communities alongside chemical parameters in Danube Delta systems after industrialization period in the context of compliance with Water Framework Directive requirements. The Danube basin has been subject to some important ecological changes, caused mainly by: hydrotechnical works, the built up of two large reservoirs (Iron Gates I and II) for hydrotechnical power plants, the conversion of floodplains into agricultural lands, opening the Danube-Black Sea canal which linked Cernavoda to Agigea, multiple uses of chemicals in agriculture which enrich the Danube waters fertilizers and pollutants, navigation development, uncontrolled tourism. The survey was done along Danube and Danube Delta (St. Gheorghe Branch) based on field experiments over 10-years (2003-2013), researches and national reports before and after industrialization period. The main problems identified in the basin were: contamination with hazardous substances, contamination with substances that enhance the heterotrophic organism’s growth, oxygen depletion, microbiological contamination, high nutrient loads and eutrophication. Those changes affected the biocenosis structure reflected by biodiversity reduction, the loss of the equilibrium between plankton species – benthos fauna, the algal blooms causing eutrophication, diatoms abundance, and loss of sensitive taxa, high number of endangered species and the decrease of biological productivity. The results assessment will allow the present ecological status to be redefined.