Łączność hydrologiczna, strukturalna i ekologiczna funkcjonalność meandrującego ekosystemu delty Dunaju

Abstrakt

The pressure control of the climate change and anthropogenic factors have consequences on the ecological systems, generating structural changes. The abiotic (i.e., water hydrology and hydraulics, sediment load, water physic-chemistry) and biotic (i.e., biodiversity, structure and functionality of food webs) characteristics of river-channels-lakes from deltas depend on several factors; however, the main driver of these characteristics is represented by the hydrologic connectivity with the main stem of the river. Floodplain lakes can be permanently, temporarily or disconnected with the main stem of the river producing interruptions in the transfer of fresh water and thus affecting benthic macroinvertebrates, by decrease in their population, diversity and even loss of sensitive taxa. Multidisciplinary investigations (hydrodynamics, sedimentological and ecological measurements and analyses) were made to investigate a river-channel-lake site type situated on the St. George branch formed by a cutoff meander (Mahmudia meander), a connective channel (Uzlina Canal) and a lake (Uzlina Lake) to observe how much the fresh water and sediment input to the delta depressions is affected by the structural changes of the meander physiography. The Mahmudia meander was rectified 40 years ago and the response of the channel consisted in a very fast silting of the former meander, currently receiving less than 5% of the upstream water and sediment discharge. The lateral connectivity with the deltaic depressions thought the lateral canals is compromised.