QUANTITATIVE AND QUALITATIVE EVALUATION OF ZOOBENTHOS IN THE ROSCI0066 DANUBE DELTA - THE MARIN AREA SITE – A CASE STUDY IN VERNAL SEASON 2012

Zoobenthos plays an important role in the proper functioning of aquatic ecosystems. Benthic animal organisms may have a role in filtering water, remineralisation of the organic matter but also can be used as feed for fish or human food. To assess the qualitative and quantitative structure of zoobenthos in ROSCI0066 site, in vernal season 2012, benthos sampled were taken on sedimentary substrate at depths between 8 m and 18 m, with Van Veen bodengreif. The species were identified up to species level or group and for quantitative analysis the individuals were counted simultaneously with the sorting and their identification. Density was expressed in individuals per m2 and biomass in g m-2. In vernal season 2012, in ROSCI0066 site have been identified 20 species of benthic invertebrates, mostly polychaetes (50%), followed by mollusks (bivalves and gastropods) (40%), crustaceans (5%) and other groups (5%). In quantitative terms, the values of zoobenthos density and biomass showed variations ranging from a minimum density of 50 individuals m-2 (Mila 9) and a maximum of 2575 individuals m-2 (Periboina) or a minimum biomass below 1 g m-2 (Sulina, Mila 9 Perisor) and maximum of 530 g m-2 (Periboina). Compared with the previous year, in the ROSCI0066 Danube Delta - the Marin Area site is recorded a decrease of the number of zoobenthos species from 36 to 20 species