SS3.15 Physical Forcing and Pelagic-Benthic Interactions in Aquatic Systems
Date: Thursday, June 13, 2002
Time: 10:30:00 AM
Location: Oak Bay
 
PerkinsRG, University of St Andrews, St Andrews, United Kingdom, rgp@st-andrews.ac.uk
Sun, H, , University of Aberdeen, Aberdeen, United Kingdom, hongyue.sun@abdn.ac.uk
Paterson, D, M, St Andrews University, St Andrews, United Kingdom, dp1@st-andrews.ac.uk
Watson, J, , University of Aberdeen, Aberdeen, United Kingdom, j.watson@eng.abdn.ac.uk
Gust, G, , Technical University of Hamburg, Hamburg, Germany, gust@tu-harburg.de
 
The use of in-line laser holography in the analysis of sediment erosion
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Coastal sediment stability has been studied using measurement of the critical shear stress required to initiate particle erosion. Analysis has included biogenic stabilisation by benthic biofilms, resulting from algal production of extracellular polymeric substances (EPS), which forms a gel-like matrix at the sediment surface. This study extends previous work, by investigating the nature of eroded particles using in-line laser holography. A ruby red laser was passed through a microcosm erosion chamber in which artificial or natural sediments were eroded. Holographic images of the particle field above the sediment were recorded, to examine eroded particles independently and as part of the “erosion field”. Sediments with different concentrations of added EPS and with biofilms grown in situ, demonstrated the importance of EPS in determining the tertiary structure of eroded floc. Data presented includes analysis of the fine-scale structure of sediments, critical stress measurements and the nature of the eroded material. This combined approach of LTSEM and holography under controlled stress conditions gives new information on the mechanisms of biogenic stabilisation by polymer secretions. Initial holography has shown good resolution, discriminating between EPS, sediment particles and diatom cells, showing the erosion process using particle field holography for the first time.