INFLUENCE OF REGIONAL CHANGE ON BIOLOGICAL ASSEMBLAGES IN THE DANUBE DELTA

Catalina Stoica, Elena Stanescu, Irina Lucaciu, Stefania Gheorghe, Margareta Nicolau, National Research and Development Institute for Industrial Ecology – ECOIND, Romania

Abstract

The effects of regional changes on the water quality of the Danube Delta (St.Gheorghe Branch) were investigated using the causal framework DPSIR, model used for describing the interactions between society and the environment adopted by the European Environment Agency (EEA): Driving forces, Pressures, States, Impacts, Responses. It is known that interactions between climate change and other drivers of change including hydromorphological modification, nutrient loading, acid deposition and contamination by hazardous substances represents sources of environmental pressures for biological assemblages. This study was done by surveying the ecological status described in EU Water Framework Directive (EU-WFD) using the biological quality elements: composition and abundance, diversity, sensitive/tolerant species, biomass (phytoplankton, macro invertebrates) in one of the most productive socio-ecological system.
The assessment of biological assemblages was based on laboratory data, results of field experiments over three-year period (2009-2011) and aspects of hydrophysical, hydrochemical and ecological change, those being early indicators of climate change in aquatic ecosystems.
Under reduced flow, combined with increasing temperature, phytoplankton biomass increased; in contrast the flood pulses have caused dilution effects on nutrients, and therefore significantly lower phytoplankton biomass. The floods and changes in flow regimes have also, an impact on the bed and bank structures, so the benthic macro invertebrates diversity was reduced, was observed the loss of sensitive taxa and changes in comunnity composition.
A strong reduction in nonpoint inputs of pollutants would be necessary to be counterbalance the possible climate-induced effects on biological assemblages.

Keywords: Danube Delta, water quality, biological assemblages, climate change, disturbed environment