[On the colonization of brackish water by marine animals of different ecological origin]

Since animals of the marine littoral and supralitoral zones tolerate greater salinity-fluctuations than those of deep water layers they are far better adapted to colonize estuaries and brackish waters.This is why there live only few animals from the seabottom in brackish water even if it is very deep. Only animals from the littoral invade water with low or fluctuationg salinities.Those which are not restricted to surface regions (by their food - many depend on green plants) extend their range in brackish waters into deep layers since there is almost no competition.Therefore the bottom communities of the sea differ very much from the bottom communities of deep brackish waters.The extension of the range of marine littoral animals in deep brackish basins ("Brackwassersubmergenz") therefore is characteristic for deep brackish-water-zones and no special case of the Baltic Sea.