WIND-INDUCED AND TIDE-INDUCED RESUSPENSION OF SEDIMENT AND MICROPHYTOBENTHOS FROM TIDAL FLATS IN THE EMS ESTUARY

The resuspension of microphytobenthos (mainly benthic diatoms) and mud (< 55-mu m fraction) from tidal hats was studied in the Ems estuary ( Netherlands/Germany, of which similar to 50% is covered by intertidal areas. Mud and microphytobenthos are resuspended simultaneously from t he tidal flats in the estuary. The concentrations of these parameters in the main channels of the estuary are strongly affected by erosion d ue to wind-induced waves and by settlement during calm weather conditi ons. The resuspension of mud can be described as a linear function of the ''effective windspeed,'' which is defined as the windspeed average d over three high-water (6 h bracketing high water) periods preceding sampling. The resuspended fraction of microphytobenthos from the top 0 .5-cm layer of sediment can also be described as a linear function of the effective windspeed. Our data indicate that for this estuary, the proper quantification of resuspension of mud and microphytobenthos req uires consideration of relatively large areas.