The Lithological Composition of the Bed Sediments Collected Along the Sf. Gheorghe Branch (km 85 - km 15) (Streams, Artificial Canals, Rectified Meanders, Including Lateral Channels and Lakes), Danube Delta, Romania

The Sf. Gheorghe distributary (the oldest branch of the Danube River) is subject to different hydro - sedimentary impacts due to the anthropogenic meander cut - off plans undertaken in the last decades for navigational purposes. This study aimed to determine the contents of the main lithological levels (i.e., organic matter – TOM%, carbonates – CAR% and siliciclastics – SIL%) in the bed sediments, using the LOI (Loss in Ignition) method. In this sense, a field sediment investigation has been conducted in 58 sampling sites located on the Sf. Gheorghe Arm (km 85 – km 15) (rivers, artificial channels, rectified meanders, including side channels and lakes), during May 2024. The distribution of the organic matter, carbonates and siliciclastics showed a significant spatial variability. The implemented analyses made it possible to distinguish mineral - rich sediments (>15 - 30%SIL) found especially in river sections, while organic - rich sediments (>15 - 30%TOM) were mainly identified in lakes. From these outcomes, it seems reasonable to conclude that the sediment deposition and accumulation are strongly influenced by the local hydrodynamic conditions (fluvial and lacustrine environments) which allow the accumulation of a mixture of different sediments. This study enables quantitative evidence related to the main lithological components of the bed sediments within the Sf. Gheorghe Arm (km 85 – km 15), and present a database for future sustainable ecosystem restoration and management measures, to protect and maintain wildlife habitat and biodiversity on the Danube Delta edifice .