Long-term changes in cladoceran assemblages in the Danube floodplain area (Slovak–Hungarian stretch)

Abstract

In this paper, the distribution of Cladocera species in the different sampling sites: the main channel/old river bed, parapotamal type side arms and plesiopotamal side arms, is described. The structure of cladoceran assemblages in the by-passed Danube section and in the adjacent floodplain water bodies has changed since the Gabcˇı´kovo hydropower plant was put into operation. Great changes have been observed in the previous parapotamal side arm situated between river km 1840 and 1820, artificially fed with water from the head-race canal. The dominance of tychoplanktonic (benthic and phytophilous) species has increased, while the typical euplanktonic species have disappeared. Three characteristic groups of cladoceran assemblages were recorded when a different type of habitat was taken into consideration. Euplanktonic cladocerans prevailed on all sampling sites before damming. In periods after damming, littoral species, and later also a euplanktonic forms, dominated on the main channel sampling sites. In parapotamal and plesiopotamal side arms with rich littoral macrovegetation during periods after damming, phytophilous cladoceran species were the ones with the highest occurrence. The samplings from the first time period were rather homogenous. The samplings from the second and third period were more similar when considering the sample site than regarding the time period. In total, 64 cladoceran species were recorded in the course of 13 years (from 1991 to 2004). The increase in number of Cladocera species from 1991 to 2004 was significant. Chydorus sphaericus was found to be the most widely distributed species in the study area. The finding of Disparalona hamata is the first faunistic record from the central part of the Danubian watersheds.

Younger Dryas Cladocera assemblages from two valley mires in central Poland and their potential significance for climate reconstructions

“…It seems that this situation resulted from the rich macrovegetation that covered the littoral zone, allowing an increase in the number of macrophyte-associated species. Similar changes in cladoceran assemblages were reported by Illyova & Nemethova (2005) from the Danube floodplain area. An increase in macrophyte abundance has a large impact on cladoceran communities (Sweetman et al, 2010); it supports an increase in phytophilous cladocerans.…”

Zooplankton in a Danube River Arm near Rusovce (Slovakia)

“…The number of cladoceran (34) and copepod (16) species is relatively high and corresponds with other Danubian arms (Gulyás 1994;Bothár & Ráth 1994;Illyová & Némethová 2005). The number of cladoceran species found in the Rusovecké rameno arm represents as much as a half (54%) of all the species recorded in a (15 years) long-term monitoring of cladoceran assemblages in the Danube floodplain area (Illyová & Némethová 2005).…”

“…The number of cladoceran species found in the Rusovecké rameno arm represents as much as a half (54%) of all the species recorded in a (15 years) long-term monitoring of cladoceran assemblages in the Danube floodplain area (Illyová & Némethová 2005). Similarly, the number of copepod species in the arm is a half of the number of species (30) recorded in monitoring of the Danube river-basin waters by Vranovský (1997).…”

“…Zooplankton assemblages of the leftbank area in Slovakia were also investigated (e.g., Vranovský 1974Vranovský , 1975Vranovský , 1985Vranovský , 1991. Cladocera and Copepoda assemblages in the Danube floodplain area are well-recorded for the long-time monitoring area influenced by hydro-electric power plant operations (Vranovský 1997;Illyová & Némethová 2005).…”

Crustacean plankton abundance in the Danube River and in its side arms in Hungary

“…Present study confirmed the expansion of this species. In Hungary, Pleuroxus denticulatus has only been reported from the Szigetköz region (Gulyás & Forró 1999), but has been depected as an invador in the Slovakian floodplain area (Illyová & Némethová 2005). The dominance of the smallbodied cladoceran Bosmina longirostris, nauplii and copepodites are in keeping with the findings of Gulyás (1994Gulyás ( , 1995 and Bothár (1978Bothár ( , 1994 but the relative contribution of copepodites is rather low in this study (it is almost equal to those of adult copepods), nevertheless, Bothár (1978) got to similar results.…”