Long-term changes of intertidal benthic assemblages in the mesohalinicum of the Weser Estuary

Long-term changes of intertidal benthic assemblages in the mesohalinicum of the Weser estuary were studied by a comparison of survey data from 1968, 1980 and 1992. By means of a cluster analysis eight benthos-assemblages could be identified and described. The changes of the distribution patterns of the assemblages and of individual species indicate a shift of the estuarine benthic community in the upstream direction. One of the main changes observed in the period from 1968 to 1980 was a strong decrease of the brackish water alga Vaucheria sp. In 1992 an invasion of Marenzelleria cf. wireni became visible. The differences of the winter discharges before the sampling campaigns, the long-term increase of salinity and the changes of sediment composition and structure are proposed to be the major causes for the observed changes of benthos in the estuary.