Abstract
This study, analyzes the benthic macroinvertebrates community structure and composition in order to assess the ecological status
as required by the Water Framework Directive (WFD). Macroinvertebrates are the appropriate indicators to describe habitat
heterogenity and the water bodies ecological status by turning the allochtone material into biomass, which is then transferred to
the upper trophic levels. Moreover, the macroinvertebrates have the capacity to integrate in their structure the effects of
environmental pressure at a temporal and spatial scale. In this particular case, the spatial scale is represented by the Danube
Delta, Saint (St) Gheorghe Branch with a length of 112 km, carrying 22% of the Danube flow. The samples include all the
organisms life cycle and were collected each month from July to October 2012. The structure and composition of
macroinvertebrates were the main target of this study. Furthermore, the structural response of macroinvertebrates to
environmental pressure was characterized by quantitative and qualitative analysis.
Also, the ecological status was assessed by a surface water bodies methodology in accordance with WFD. This present study
brings new information of the benthic community structure and dynamics, reflects the long-term effect of environmental
pressure, and it is an effective tool for evaluating integrative ecological status of lotic aquatic systems.