Using dissolved and particulate carbon for the prediction of soft sedimenterodibility

Various investigations into soft sediment transport have shown recently tha t the growth of benthic microorganisms on cohesive sediments can influence the erosional behaviour of the bed material. The formation of biofilms and microbial mats on mud banks has been reported to occur in estuaries and res ervoirs. Most benthic microorganisms produce and exudate extracellular poly meric substances (EPS). These exudates serve as connection between cells an d sediment particles and form the amorphous biofilm matrix in which the org anisms are embedded. A variety of biological parameters (i.e. photopigment content, number of cells) has been used to correlate the biological status of the bed with the erodibility of the sediments. This article deals with t he utilization of dissolved and particulate organic carbon to perform this correlation. Experiments were carried out in a small in-situ-device. Biofilms (microbial mats respectively) consisting of pennate diatoms and filamentous cyanobact eria were established on a pure caolinite bed. The shear stress was increas ed stepwise in order to ascertain the critical shear stress for erosion. Pa rticulate organic carbon (POC) was determined by means of a CHN-elemental a nalyzer. Dissolved organic carbon (DOC) could be determined using phenol an d sulfuric acid. (C) 2000 Elsevier Science Ltd. All rights reserved.