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MICROBIALLY MEDIATED PROCESSES IN TIDE-INFLUENCED DEPOSITS AND THEIR IMPORTANCE IN STABILISATION AND DIAGENESIS OF SEDIMENTS

Objective


Microbial mats and biofilms contribute towards sediment stabilization and inland arch build up in the northern seas. For continuous monitoring of sediment stabilization, primary productivity, grain size distribution, chemical parameters, organism composition and succession, and the determination of growth related factors, several sampling sites have been selected, in the Bristol Channel, on the Dutch island of Texel, and on the German Wadden Sea coast. Samples were also taken for metal and mineral analyses.

Laboratory model systems were developed and mats sufficiently stable for cohesive strength measurements were cultivated. The results were compared with the cohesive strength of natural mats. Two new systems for measuring cohesive strength were developed and tested.

It was concluded that the fine sediments of the Severn Estuary, stabilized by extracellular polymeric substance produced by epipelic chiatom assemblages, were more easily eroded than the German or Dutch mats, stabilized by the triple action of mineral formation, filamentous network formation and extracelluar polymeric substance production and subsequent desication. Predicative values for the threshold stress for particle entrainment based on sedimentological parameters underestimated the measured threshold stress for erosion by up to 10 fold, emphasizing the seasonal and spatial importance of mat formation and biogenic stabilization.
PROJECT DESCRIPTION:
Microbial mats and biofilms stabilize sediment surfaces of intertidal and other sediment surfaces (e.g. hardgrounds). The increase of stability and the resistance to different erosional forces of such microbial mat stabilized sediments is of high interest for coastal engineering and accretion of sedimentary systems in near-shore environments. The stabilizing and global flux related effects of microbial mats built by diatoms, cyanobacteria and in some cases, macroalgae will be studied at four major sites: (1) Bristol channel, (2) Dutch Wadden Sea,(3) German Wadden Sea and (4) in artificial mat systems built in the laboratory. Biologically stabilized sediment surface layers presently are the least well known portions of the sedimentary column of shallow seas. The study of biological flux of trace elements and compounds through this boundary will enable us also to estimate man-made pollutant fluxes. We will examine structure and function of sediment stabilizing microbial mats using microelectrode and cultural techniques, to describe mathematically the function and structure of biologically cohesive sediments, to carry out geochemical analyses within such biomediated sedimentary systems, to determine the mechanical parameters of sediment stabilizing microbiota, to measure the physiological characteristics of the microbial mats and to study the interaction of sediment binding cyanobacteria with anthropogenic compounds and mass transfers.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

UNIVERSITY OF OLDENBURG
Address
Ammerlaender Heerstrasse 114/118
26129 Oldenburg
Germany

Participants (3)

Federal Institute for Geosciences and Natural Resources
Germany
Address
Stilleweg 2
30655 Hannover
UNIVERSITEIT VAN AMSTERDAM
Netherlands
Address
Spui 21
1012 WX Amsterdam
University of Bristol
United Kingdom
Address
Senate House Tyndall Avenue
BS8 1TH Bristol