Adapting floodplain connectivity conditions – a prerequisite for sustaining aquatic macrophyte diversity in the UNESCO Biosphere Reserve Lobau (Austria)

The UNESCO Biosphere Reserve Lobau (Austria), established in 1977 within the city limits of Vienna, is part of the Danube National Park and one of the ecologically richest parts of the Danube River Corridor. Hardly noticed by diverging stakeholder interests the smaller aquatic habitats in the floodplain area are acutely threatened by wetland ageing and terrestrialisation processes. In 2007 an aquatic plant survey was carried out in the water bodies of the active floodplain on the left bank of the Danube main river channel as well as in the semi-separated water bodies of the Lobau. Results clearly show the impact of through-flow on aquatic plant species composition and abundance, as these metrics are significantly higher in the semiseparated location. Suitable water regime for all sensitive aquatic plants is an essential prerequisite for sustaining aquatic macrophyte diversity in the Lobau Biosphere Reserve, and could provide an ecohydrological basis for rehabilitation activities in other regulated river floodplains located in cultivated landscapes.