HYDRO-ECOLOGICAL QUALITY STATUS ASSESSMENT IN DIFFERENT LAKES OF DANUBE DELTA – ROMANIA. CASE STUDY: UZLINA, ISACOVA, MATIŢA, BABINA AND ROŞU LAKES - 2010

Irina Catianis*/***, Priscila Opreanu***, Dumitru Grosu**

*University of Bucharest, Faculty of Geology and Geophysics,Bucharest, Romania
**National Institute of Marine Geology and Geoecology – GeoEcoMar, Bucharest Romania
***National Institute of Marine Geology and Geoecology – GeoEcoMar, Constanta Romania

Abstract

The aim of this study is to provide a precursory estimation regarding the water and sediment quality of some lakes in the framework of the Danube Delta. The region of Danube Delta is a peculiar land, being crossed by many canals, streams, swamps and including many lakes which represent unique ecosystems which provide and sustain habitats for plant and animal communities. Due to the upstream anthropogenic activities, delta lakes are subjected to susceptible pollution, taking into account that Danube River is receiving considerable quantities of industrial, agricultural and urban wastewaters. In order to assess the hydro-ecological status of deltaic lakes, two sampling campaigns were performed during 2010 and the following measurements were fulfilled: water physico-chemical parameters (oxygen concentration, pH, electrical conductivity, total dissolved solids, nitrates, nitrites, phosphates and sulfates), main lithological parameters of sediments (total organic matter, carbonates and siliciclastic fraction) and biological assay (identification of benthic communities). The basic results show that the analysed aquatic systems are actually controlled by external factors as: lake morphology, variation of climatic parameters, and lake position within the deltaic hydrological network (directly influenced by the Danube River input or located farther on the fluvial input). Physico-chemical measurements performed on lakes and connection canals indicate small variations ranges. In some samples were incidentally noted lower concentrations of oxygen content and pH fluctuations from slightly alkaline to alkaline domain. Chemical recorded data does not present high concentrations for nitrates, nitrites and sulfates. Regarding the phosphate content, some higher values have been investigated. Generally, the physico-chemical records report normal values which are in accordance with surface water quality standards. The lacustrine sediment cores exhibit uniform profiles, display a homogenous color (from light grey brown to dark grey brown) and sometimes with evidence of layering. Sedimentologically (textural and structural), these bottom sediments correspond to the group which diverge from silty to silty clayey (fine and very fine), alternately sometimes with sandy deposits. Distribution of the main lithological components noted a similar trend for every studied core, meaning a high percentage of organic matter at the top, a subsidiary low content of carbonates and a complementary siliciclastic sediment fraction. The biological findings show some sensitive sectors (small number of taxa) which may suggest a degradation of the aquatic environment (poor growth of some species). Overall, the implemented study fulfilled in 2010 shows a normal status for such aquatic systems with undetectable contamination evidences.

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