An estimation procedure for suspended sediment concentrations based on the intensity of backscattered sound of acoustic Doppler current profilers (ADCP) is introduced in this paper. Based on detailed moving and fixed boat ADCP measurements with concurrent sediment sampling, we have successfully calibrated the estimation method for a reach of River Danube in Hungary, characterized by significant suspended sediment transport. The effect of measurement uncertainty and various data filtering on sediment load determination is also analyzed and quantified. Some of the physical model parameters describing the propagation of sound in water are estimated based on known empirical formulas, while other parameters are derived from measured. Regression analysis is used to obtain a relationship between the intensity of backscattered sound and sediment concentrations. The empirical relationship has been then used to estimate the suspended sediment concentrations from the ADCP data collected in fixed and moving boat measurement operation mode, along verticals and path-lines, respectively. We show that while some measurement uncertainty is inherent to the acoustic Doppler principle, it is further enhanced by the complexity of the near-bottom sediment-laden flow. This uncertainty has then a significant effect on the local sediment load estimation. In turn, reasonable smoothing of raw velocity and backscatter intensity data shows insignificant impact on cross-sectional sediment load estimation.
In early spring of 2007, unusual feeding behaviour was observed for the Eurasian otter (Lutra lutra) when a cache of toads (n = 18), black bullheads (n = 2) and great diving beetles (min. 58 ind.) were found in a hollow tree-trunk on the shores of an oxbow lake near the River Danube. Spraint analysis identified the primary food of otters in the area to be fish, with non-fish (buffer) prey of very low importance. As the otter consumed almost exclusively fish, and appeared to store mainly buffer food items, this may indicate that either preferred fish were less available (limited) or that non-fish items were relatively more abundant for a short period during the mild ‘cold’ winter and spring period. The otter had abandoned this particular cache. Food caching is an important dietary adaptation for many species, providing readily available food during periods when fresh food may be difficult to find.
Diskutovány jsou tři drobné nálezy z Čech připisované tzv. köttlašské kultuře, resp. karantanskému okruhu. U náušnic či ozdob hlavy z Lékařovy Lhoty (okr. České Budějovice) a Nových Dvorů (okr. Beroun), pocházejících asi z desetiletí kolem půle 9. stol., je uvedený původ pravděpodobný, při jejich přenosu do Čech se uplatnila trasa Podunajím. Naproti tomu u malé hlavice se zbytkem dříku z Libice (okr. Nymburk) se uvažovaná souvislost s emailovanými ozdobami mladší köttlašské kultury zřetelněji neprojevuje. and On the origin of several early medieval finds in Bohemia. The work discusses three small finds from Bohemia previously attributed to the Köttlach culture, or the Carantanian cultural sphere. Such probable origin is presented for earrings or head decorations from Lékařova Lhota (České Budějovice distr.) and Nové Dvory (Beroun distr.); the finds likely date to the middle of the 9th century and were probably brought to Bohemia along the Danube Valley route. On the other hand, a small capital with the remnants of a stem from Libice (Nymburk district) did not demonstrate the speculated connection with the enamelled ornaments of the Late Köttlach culture.
The tubenose goby has been reported to be the first non-native postglacial gobiid immigrant from the Lower Danube refuges. It is thus a pioneer species that was the forerunner of the extensive invasion of Ponto-Caspian gobies that ascended the River Danube and spread across Europe a century before other goby species. It appears that recently the tubenose goby invasion has accelerated. In this paper historical data on the distribution of the tubenose goby, together with data from extensive monitoring of fish communities in Slovakia are examined to evaluate both the temporal and spatial aspects of tubenose goby distribution dynamics. Until the 1990s, the species was recorded only in the River Danube and small water bodies in the Danubian Lowland (Slovakia). Since then the tubenose goby has spread upstream into tributaries of the River Danube. It was also recorded in several streams in eastern Slovakia after 2014, and the spatial data demonstrate that the tubenose goby has been colonising new water bodies, progressing to the north and ascending rivers, reaching higher altitudes than previously reported. These findings suggest that the tubenose goby deserves attention, even after two centuries following the onset of its invasion, and its further expansion across Europe should be carefully monitored.