The influence of oysters on marsh structures by image processing : Studying the influence of oysters on creek structures in European and American marshes by image processing
Legrand, S. (2019). The influence of oysters on marsh structures by image processing : Studying the influence of oysters on creek structures in European and American marshes by image processing
. MSc Thesis. NIOZ Royal Netherlands Institute for Sea Research: Yerseke. 63 pp.
In the Unites-States, many salt marshes can be found and become the source of great scientific studies not only on the ecosystem diversity but also on their morphology. This morphology is subject to directly the tide power which determine the complexity of the stream via erosion. Furthermore, oyster populations have settled within streams in large number which brings the question to know if the presence of oysters could be a parameter of structural differentiation between marshes with or without oysters. Consequently, with their number and their agglomeration on the stream edges, how can oysters influence the intensity of erosion on streams? For that purpose, the study focuses on two marsh locations which are first in the Unites-states with the presence of oysters and in the second in the Netherlands in the absence of oysters. Thus, the goal is to compare these two locations and analyse the influence of oysters on creek structure. The study of oysters showed they concentrate mainly on more or less submerged areas such as stream slope portions. Besides, Oysters have the capacity to elaborate a cement of calcium carbonate between them and sediments which consolidate the zone. Thus, this study concentrate on the strengthening of stream edges over the stream order. In seeking to compare the locations from DEM, the choice is evaluated their morphological complexity. To this end, the reflection on the main structure of marsh is raised by means of the stream sinuosity. Then by geomorphometric data, the observation is directed towards the three characteristics related to erosion that are the stream width, the slope and the elevation between stream bottom and the highest point of stream edges. The treatment on the sinuosity throughout the different orders allows to discover a disparity in the complexity of marshes with or without oysters. Thus, the American sites show a aspect more linear than the Dutch sites. This discovery notes a simplification of the creek structure in marsh which could allow to maintain this environment over time.
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