In this study we evaluate how variations in taxonomic composition and physical structure of macrophyte stands affect plant-dwelling chironomid assemblages in highly variable macrophyte assemblages in two densely vegetated backwaters. By using multivariate explanatory techniques we found that similar vegetation composition did not unequivocally relate to similar chironomid assemblages, moreover the diversity of macrophyte stands did not correlate with the taxonomic diversity of chironomid assemblages in the backwaters investigated. Taxonomic composition and structural characteristics of the vegetation had little influence on the taxonomic or functional (i.e. feeding groups) composition of chironomid assemblages inhabiting them. Similarly, there are only weak relationships between the distribution of certain chironomid species or functional feeding groups and the environmental variables investigated. In general, the structure of the vegetation was more closely associated with the distribution of dominant chironomid taxa than compositional variables (i.e. density of specific macrophyte taxa). In summary, the structure of aquatic vegetation (i.e. position, size of a stand of vegetation, total plant density) and characteristics of the environment where it develops may be more important in shaping plant-dwelling chironomid assemblages than the taxonomic composition of the vegetation., Mónika Tóth ... [et al.]., and Obsahuje seznam literatury
Vegetation in the river Danube was studied in 1972–2001 to document the changes associated with the construction of a water reservoir. Before 1993, only a single species of aquatic plant, Potamogeton pectinatus, was known to occur in the main channel of the river Danube, which forms the frontier between Slovakia and Hungary. In the 1980s the building of the Gabčíkovo hydroelectric power station started and was finished in 1993. At present, five different aquatic habitats occur in the study area. (i) In the upper part of the Čunovo reservoir, there are stands of reed; Zannichellia palustris and Elodea nuttallii were the first other macrophytes to colonize this area where there are now 11 species. (ii) The Old Danube consists of shallows and margins of the original riverbed, which since 1992 (1851–1811 river km) were occupied predominantly by Zannichellia palustris. The adjacent pools were colonized by Elodea nuttallii, Potamogeton species, Batrachium trichophyllum, Ceratophyllum demersum and Lemnaceae species, and Phalaris arundinacea dominates the littoral areas. (ii) The bypass canal harbours only the moss Cinclidotus riparius growing on the boulders. (iv) Two seepage canals were rapidly overgrown by macrophytes, many species of which were threatened species in Slovakia (Apium repens, Groenlandia densa, Hippuris vulgaris, Chara species). (v) Succession occurred in river arms on the left bank after the damming of the river which resulted in changes in spatial distribution and species composition of macrophytes; a North- American alien species Elodea nuttallii spread rapidly there.