Benthic foraminiferal assemblages in surface sediments of the Elbe estuary

Two foraminiferal assemblages are observed in surface sediments of the Elbe estuarv. an Elphidium excavatum assemblaae and an Ahmonia/Protelphidium assemblage. They are the result of test-size sorting in accordance to the grain size of the sediments. These assemblages of mainly empty tests differ basically from the living population, which is dominated exclusively by E. excavatum. The average test size is decreasing when advancing from the Open sea into the estuary and the living fauna disappears near the entrance of the Kiel Canal. In the dead assemblage the diversity is distinctively higher and the average test size varies with the grain size of the sediment. The assemblages found in plankton tows are nearly identical with those in corresponding bottom samples. This indicates the distribution pattern to be caused by transport in currents (mainly in suspension). This type of foraminiferal assemblages characterize macro- and mesotidal estuaries and might indicate a high tidal range when observed in sediments of fossil estuaries.