Large river ecosystems: Concepts and biodiversity, with special emphasis on the Danube and the International Association for Danube Research (IAD)
The investigation of large rivers is a difficult task world-wide, given the dimensions of these complex ecosystems and hence the sophisticated and laborious methodology needed for their study. Not surprisingly, most concepts in running waters have been developed for rather small rivers and streams. However, because there is neither a sharp border to, nor an exact definition of large rivers, the continuum concept and catchment approach, for example, both ultimately include large rivers. It is therefore justified and, in respect to the important issue of scaling, even necessary to compare the present knowledge on large river ecosystems with that of streams.