Dynamics of the biotic components in the aquatic ecosystems from the Danube Delta biosphere

The dynamic equilibrium of the aquatic ecosystems is accomplished because of the connections between the species and the environmental conditions and also because of the mutual connections between the existing populations. From this point of view, the study of biotic – phytoplankton, zooplankton and/or benthonic components – from the position of the systemic method and conception, in order to characterize the dynamics and role within the integrated aquatic ecosystems represents a proprietary problem of the research in ecology. The paper presents the research results regarding the biological analyses of the aquatic ecosystems of the Danube delta in two sampling sites: Uzlina and Murighiol for the samplings period April 2003 – August 2006. Investigations of the biological properties of water and sediment samples from Uzlina and Murighiol control sections have been accomplished from the viewpoint of phytoplanktonic, zooplanktonic and benthonic macroinvertebrates components and the analysis of the biotic communities in the sampling site was focused on the quantitative (numerical density, biomass, abundance after numerical density and biomass) and qualitative components (dominant species, indicator species).