The influence of mobile macroalgae on the erosion of cohesive sediments
LE3 .A278 2000
2000
Amos, Carl Daborn, Graham
Acadia University
Master of Science
Masters
Biology
The influence of mobile fragments of macroalgae of the species ' Chondrus crispus' and 'Furcellaria lumbricalis' on the erosion of prepared artificial cohesive beds was investigated in a Mini Flume. The purpose of the study was to describe how mobile fragments of macroalgae were transported at varying current velocities, and to determine whether their transport had the potential to significantly alter the erosion of cohesive beds. Algal fronds were divided into three sizes and abundances and each trial was replicated three times to determine intrinsic variability and to allow for statistical analysis. There was a high degree of variability in the suspended sediment concentrations and erosion rates within treatments. This was attributed to: (1) variation of the average settling rates of algae used in the trials; (2) variation of algal velocities with respect to current velocity; (3) variability of the morphologies and structural rigidities of the algae used; (4) variation in percent contact of the algae withthe bed; and (5) interactions between algal fronds. Results showed that mobile algal fragments significantly increased erosion rates and suspended sediment concentrations over those of the control experiments, in which there was no apparent fluid induced erosion of the bed, and that erosion rates and suspended sediment concentrations varied directly with respect to algal size and abundance. Mode of algal transport varied with current velocity and species; however, a general trend was observed: motion began by sliding and rolling, followed by a mixture of suspension and sliding and then by continuous suspension of the macroalgae. The study concluded that mobile macroalgae moving as bedload have the potential to significantly increase erosion rates and suspended sediment concentrations of cohesive sediments within the lagoon of Venice, Italy.
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https://scholar.acadiau.ca/islandora/object/theses:3073