INFLUENCE OF DRIVING FORCES ON BIOTIC COMMUNITIES IN LOTIC AQUATIC SYSTEMS (SOUTH-EASTERN OF DANUBE DELTA)

Catalina Stoica, Elena Stanescu, Irina Lucaciu, Stefania Gheorghe, Margareta Nicolau

National Research and Development Institute for Industrial Ecology - ECOIND, Romania

Abstract

It is known that interactions between drivers of change including hydromorphological modification, nutrient loading, acid deposition and contamination by hazardous substancesand climate change represents sourcesof environmental pressuresfor biotic communities.This studywas done by surveying the ecological status described in EU Water Framework Directive using the biological quality elements: composition and abundance, diversity, sensitive/tolerant species, biomass (phytoplankton, macro invertebrates)inone of the most productivesocio-ecological system. The assessment of biological assemblages was based onlaboratory 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 significantlylower phytoplankton biomass.The floods and changes in flow regimes have also, an impact onthe bed and bank structures, so the benthic macro invertebratesdiversity was reduced, was observed the loss of sensitive taxa and changes in community composition. A strong reduction in nonpoint inputs of pollutants would be necessary to be counterbalance the possible climate-induced effects on biological assemblages.

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