Okrzemki (bacillariophyceae) Zalewu Rzeszowskiego

The aim of the studies was to become acquainted with diversity of diatom communities developing in the waters of Rzeszowski Reservoir, taking into consideration their role as indicators of environmental quality taking autumn-spring aspect into account. The studies were being conducted at Rzeszowski Reservoir in 2007–2009 during spring and autumn season at 7 sampling sites. In total, 199 diatom taxa, from 46 different genus were founded at 7 sites at Rzeszowski Reservior (Tab. 2). The following genus were founded with the most taxa: Nitzschia (39), Navicula (24), Gomphonema (14) and Surirella (10). The largest populations were formed by: Achnanthidium minutissimum var. minutissimum, Amphora pediculus, Cocconeis placentula var. lineata, Cyclotella meneghiniana, Diatoma vulgaris, Luticola mutica, Navicula capitatoradiata, N. cryptotenella, N. gregaria, N. lanceolata, Nitzschia dissipata var. dissipata, Nitzschia palea, Planothidium lanceolatum, Rhoicosphenia abbreviata at most sites and they dominated during the both research seasons. The classification of diatoms taxa conducted on account of pH in water showed that, at all research sites, alkaliphilous diatoms were most numerous (<60%) i.e. occurring mainly in waters of pH>7. With respect to saprobity two groups of diatoms were dominant: β-mezosaprobic and α-mezosaprobic, with a distinct advantage of the first mentioned group. With respect to trophy, there was high participation of eutrophic taxa at all the sampling sites. On the basis of Red List of Threatened Species of algae drawn up for Poland (Siemińska et al. 2006) at Rzeszowski Reservoir taxa endangered at different levels were singled out. In total, 20 taxa of List Red List were found, which constituted 10% diatom flora of all the research.