The Danube is the second-longest river in Europe that is subjected to various man-made alterations, including those related to hydro-power plants. We surveyed and analyzed the presence and abundance of macrophytes in the main channel from 2582 river kilometers (rkm) to 171 rkm. We also assessed selected habitat parameters in the sampled river stretches. Sixty-eight different plant species were recorded along the entire course. Among neophytes, we found Elodea nuttallii, E. canadensis, Vallisneriaspiralis and Azolla filiculoides. Based on similarity analysis, we distinguished 15 plant communities, most of which were defined as associations, which were classified into 5 alliances and represented three vegetation classes, namely vegetation of rooted hydrophytes Potamogetonetea, the vegetation of pleustophytes Lemnetea and vegetation of marshes Phragmitetea. The number and abundance of plant species, as well as plant communities recorded in single stretches, varied along the course. Canonical correspondence analysis (CCA) revealed that environmental parameters explained 21% of plant species composition. CCA runs with neophytes explained 41% of the variance, and current velocity, water transparency, species number and bank structure were significant variables. The present study revealed that the free-running sections of the river are poor in number and abundance of plant species, whereas impounded reaches mainly show an opposite result.

This study was carried out in the Bucegi Natural Park, a protected area of the Romanian Carpathians. It aims at documenting the potential sensitivity of six widespread Natura 2000 habitat types and of all plants with conservative value (200 taxa) in the mountain area, to the changes in temperature and humidity, predicted for this century. Regional expert knowledge and environmental indicator values were considered in assessing the potential habitat’s sensitivity. The results support the evidence that sensitivity to temperature may be potentially higher for habitats at alpine and subalpine levels (bushes and grasslands) and medium for forest habitats. Sensitivity to moisture was detected as potentially high for forest habitats and as medium for bushes and grasslands at high mountain elevation. Microthermophilic plants have shown a greater share (76-79%) in alpine and subalpine communities, and the hydrophilic plants (86-96%) in forest communities. About 80% of plants of conservation value (microthermophilic or hydrophilic plants) may be potentially sensitive to predicted warming and drought and 44% of them (microthermophilic and hydrophilic plants) to the changes of both parameters. Climate scenarios (2011-2100) and sensitivity maps (Sat – image interpretation with GIS for the whole mountain area) are included.

Hydro-acoustic methods are commonly used to estimate the abundance and distribution pattern of fish in aquatic environments, while studies on the assessment of the biomass of submerged macrophytes in the littoral zones are still rare. In the present study we provide first results showing that indeed this method is a useful tool to estimate the aquatic plant stands in lakes. The aim of the recent presentation is to show an initial data evaluation by graphs describing hydro-acoustic signals at three distinct layers in a small shallow lake: the solid sediment, the fine or muddy sediment, and the ‘plant canopy’ of submerse macrophytes. The most difficulties of data processing and assessment of biomass were for hydro-acoustic records close to the water surface where the echo-signal is interfered by reflectance. Methodological details and progress in evaluating hydro-acoustic records will be discussed.