Microphytobenthos communities in the freshwater tidal to brackish reaches of the Schelde estuary (Belgium)

In late summer 1995, intertidal flats situated in the freshwater tidal and brackish reaches of the Schelde estuary were sampled to study the microphytobenthos in the upper estuarine reaches. Diatoms dominated the microphytobenthos community at all sites while coccoid green algae, flagellates or cyanobacteria never contributed significantly to total cell abundance. Epipelic and epipsammic diatoms were the dominant organisms at the brackish sites and disappeared in the oligolialine and freshwater sites, where, planktonic diatoms dominated the microphytobenthos community. In oligolialine to freshwater tidal reaches, a turbidity maximum is present which is maintained by repeated resuspension and sedimentation of suspended matter from and to the intertidal areas. Probably, this intense reworking of the sediment surface prevents epipelic and epipsammic diatoms from colonising intertidal mudflats in this part of the estuary