engleski

Floating macrophyte mat as a playground for freshwater invertebrates

One of the largest and most preserved floodplains of the Danube, Kopački Rit, has characteristic wetland habitats (lakes, channels, river side arms) that function as a highly significant subsystem of the floodplain complex. Such complexity supports very high biodiversity of aquatic organisms, influenced by the Danube’s water-regime. In July 2013, after one of the extreme floods (starting in June), waters from the parent river, trapped within the Rit, enabled the development of atypically abundant, dense, floating macrophyte mats. Sampling was conducted (with a cylindrical core) on the 2nd, 4th, 8th and 12th of July – when the canopy dispersed, at three sites in Kopačko lake and Čonakut channel. Standard physico-chemical water parameters were measured in situ, and the laboratory analyses included isolation and identification of plant material and macroinvertebrates, and chlorophyll analysis. Plant material was dried at 105°C for 24h to assess the dry weight. Twenty-seven invertebrate taxa were recorded, of what 14 belonged to Insecta. In total, 7370904 ind./100g d.w. were sampled, most abundant being Cladocera, Copepoda and Chironomidae larvae. The floating plant canopy provided perfect refugium and food source for the invertebrates. NMDS analysis (invertebrate abundance, Bray-Curtis similarity matrix) displayed the grouping of sampling dates and the statistical significance was confirmed by ANOSIM analysis. There was no difference in-between the sites or water bodies. The most important environmental parameters influencing community structure were water temperature and the Danube water-level, which decreased, thus causing the outflow of waters from the floodplain and the dispersal of this interesting community.

Freshwater macrophytes, macroinvertebrates, floodplain

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