Periphyton and phytoplankton in the soroksár-Danube in hungary. I. Periphytic algae on reed stems

Abstract

Periphyton samples from the reed-belt and phytoplankton samples were taken in November 1996 and in January, April, July 1997 at the upper part of the Soroksár-Danube (the second largest side arm of the River Danube in Hungary) at Taksony, and in July, November 1998, January, April 1999 at the middle part of the side arm at Ráckeve. The aim of this study was to investigate the seasonal and vertical distribution of periphyton growing on old and green reed stems at both parts of the side arm, focussed on taxonomic composition, abundance and chlorophyll a content. Based on the chlorophyll a content of the phy toplankton the upper part of the side arm at Taksony was oligotrophic in November and July (in July caused by a flood), mesotrophic in January and eutrophic in April. The middle part of the Soroksar-Danube was eutrophic in April and July, oligotrophic in November and January at Ráckeve. The values of abundance and chlorophyll a of periphyton were the highest at the middle part of the So roksár-Danube, while that of phy toplankton was the highest at the upper part. A few diatoms showed the same distribution along the reed stems. Relative abun-dance oi Amphora libyca, Cocconeis placentula and Eunotia arcus increased close to the bottom, while that of Gomplwnema minutnm, G. parvulum, Navicula capitatoradiata and Nitzscliia dissi-pata decreased. © 2001 Akadémiai Kiadó, Budapest.