The status of the intertidal zoobenthic brackish-water species in estuaries of the German bight

Abstract

The intertidal macrobenthic fauna of 12 estuaries and small outlets which discharge into the German Bight incorporates a total of 16 brackish-water species; at least nine other species which occur on other Northwest and Middle European coasts have not been recorded here. The species strictly limited to brackish waters are presumably very sensitive to civilization impacts, and the degree of environmental deterioration is reflected by the presence or absence of such species. The species richness found in the individual estuaries depends predominantly on habitat diversity in the meso- and oligohaline reaches in relation to the size of a brackish-water body. Consequently, species richness is relatively high in the estuaries of the larger rivers, in spite of pollution, engineering, shipping and dredging effects. In the outlets of small rivers, canals and draining ditches, however, habitat diversity is reduced to a degree far below natural conditions because most of these waters are cut off from the sea by technical constructions, and their discharge occurs by means of sluices or pumping. These artificial outlets are inhabited by a very limited number of brackish species, which in most cases belong to the less stenohaline types.