BIOGENIC INFLUENCES ON THE FORMATION AND LONG-TERM DYNAMICS OF COHESIVE SEDIMENTS

1 wrRonvCTIoxToday it is widely accepted that the PrOcesses involved in cohesive sediment transpoft are stronglyinfluenced by the biological achvity of planctic (flocculation and sedimentahon) and benthic(consolldation and erosion) orgedsms (SPOrk et al. l997; PrOchnow et al. l999). Furthennre it can notbe neglected that particulary the ProCesses of sediment aging in teW of comPosition, pore-water content,stickiness of particles and aggregates and threshold of sediment motion are affected…

BIOGENIC INFLUENCES ON THE FORMATION AND LONG-TERM DYNAMICS OF COHESIVE SEDIMENTS

Biogenic stabilization processes that result in the formation of biofilms and interparticle-networks can significantly alter the transport characteristics of flnegrained sediment layers. The increase in the threshold of sediment motion can amount to up to several hundred percent. While planctic organisms are involved in the formation of depositing flocs and the early stages of consolidation, the secondary consolidation is controlled by microbial breakdown processes, leading to changes in the mechanical properties of cohesive sediments. While the primary stage of consolidation is completed in days, the secondary processes can last for decades. A preliminary series of erosion tests in an annular flume revealed demonstrated the biogenic impact in the early stages of sediment formation. Surrogate materials were used to simulate the governing properties of natural soft sediments.