| Summary: | Laboratory and field studies were carried out to determine the effect of biofilms on sediment erodibility. The effect of growth and carbohydrate production of the diatom, Nitzschia curvilineata, on sediment erodibility was explored in the laboratory. Sediment chlorophyll and bulk carbohydrate concentrations were negatively correlated with erosion rate. An increase in bulk carbohydrate content was observed at the end of exponential phase of growth. An increase in eroded aggregate size was observed with age of biofilm, suggesting an alteration of biofilm microfabric through carbohydrate production. The critical shear velocites obtained for the base of the biofilm were greater than those obtained for the surface, suggesting an increase in strength of the biofilm with depth. An in situ flume (Sea Carousel) was deployed at stations along a transect in Upper South Cove, Nova Scotia and in Manitounuk Sound, Quebec, to examine the relationship between the biofilm components and sediment erodibility. In Upper South Cove, erosion thresholds and rates correlated with sediment chlorophyll and colloidal carbohydrate content. Erosion rate may be a more important index of sediment erodibility than erosion threshold, since erosion rates varied by a factor of 7 along the station transect while U$\rm\sb{*crit}$ varied by a factor of 2. In Manitounuk Sound, variations in the physical sediment properties along the station transect were greater than the biological sediment properties, rendering the physical sediment properties more sensitive indicators of sediment erodibility. Erosion rates were correlated with many of the sediment variables influenced by the increase in hydrodynamic energy seaward through the Sound. Thesis (Ph.D.)--Dalhousie University (Canada), 1996.
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