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Transition towards hypertrophy has affected biodiversity and productivity of most aquatic and wetland systems in the Lower Danube Wetland System (LDWS) over the last two decades. The aquatic macrophytes have been deeply involved in ecosystem reorganization in these circumstances. Representative shallow lakes and channels located in the river floodplain and delta were studied in this period in terms of space distribution, diversity, species composition, primary production and main hydrogeomorphic features (morphometrical and physico-chemical parameters). Changes in submerged vegetation dynamics along two successive decades after 1980 included diminishing areas of about 50% in the Danube Delta, restructuring primary producers by suppressing aquatic weed in some lakes or parts of lakes and decreasing species richness to few populations with upright and floating growth strategy. Biomass production showed different trends, from severe reduction in some lakes and periods to marked increase in other ones, provided by a changed and simplified species structure, generally dominated by Ceratophyllum demersum L. and Potamogeton species. It was concluded that the eutrophication effects are maintaining, modulated by diverse response mechanisms developed by submerged macrophytes. Finally, the main lessons to be learned for the management of aquatic macrophyte-dominated systems in the framework of redesigning the LDWS structures are emphasized on the basis of a large scale and long-term prospect of the Danube River and Black Sea Basins. [ABSTRACT FROM AUTHOR]

The objective of this paper is to estimate the non-market benefits of ecological river restoration and test their transferability across the second largest river basin in Europe. River restoration reduces flood risk and improves water quality, the welfare impacts of which are measured in an identical choice experiment conducted in three Danube river basin countries: Austria, Hungary and Romania. The estimated choice models differ in preference and scale parameters. Distance-decay effects are detected for water quality improvements in Austria and Romania and for a reduction in flood risk in Austria. Public perception of current water quality affects the value people attach to further improvements in water quality levels in all three countries. Controlling for these influencing factors, the estimated non-market benefits of river restoration policy scenarios appear to be transferable between Hungary and Romania, but not between Austria and Hungary and Austria and Romania. Given the role of location specific factors such as differences in population density and degree of urbanization, the use of a generally applicable research design seems a necessary, but insufficient precondition to reduce transfer errors when applying existing estimates of the non-market benefits of river restoration from the international literature to new river restoration contexts. [ABSTRACT FROM AUTHOR]