Dominant species,functional assemblages and frequency of equilibrium phases in late summer phytoplankton assemblages in Hungarian small shallow lakes

摘要

Late summer phytoplankton associations were studied qualitatively and quantiatitively in 80 Hungarian lakes altogether (mostly shallow salt lakes,reservoirs,oxbows,gravel pit lakes).Equilibrium phases sensu Sommer et al.(1993)were found only in 17 lakes.Most of them were under some kind (hgih salt content or very low level of nutrients)of stress factor.It is condluded that environmental stress forces phytoplankton communities wowards equilibrium.No relationship between occurrence of equiibria and trojphic state was found.Species unmber of nonequilibrated lakes was almost three times as high as those in equilibrium.Of the 31 recently described (Reynolds et al.,2002)phytophlankton assemblages most of those wee recognized that are likely to occur in shallow lakes.Separtion of a functional group W_S from W2 for Synura dominated lakes is suggested.It seemed also necesary to raise a proup (Y_ph)for lakes dominated by Phacotus.Soring of Dinophyta species into different already described functional groups is desirable.