Biogeomorphology of coastal seas: How benthic organisms, hydrodynamics and sediment dynamic shape tidal sand waves

There is growing recognition of the importance of feedbacks between organisms and physical forces in landscape formation; a field labeled biogeomorphology. Biogeomorphological processes typically involve so-called ecosystem engineering species, which are organisms that modify the abiotic environment via their activity or physical structures and thereby create, modify and maintain habitats. Biogeomorphological processes are known to shape a broad range of landscapes. However, in the underwater landscape these interactions have received little attention, despite the high abundance of ecosystem engineering species in the bed of coastal seas. This thesis aims at understanding the interaction between ecosystem engineering species, hydrodynamics and sediment dynamics in the formation of the underwater landscape. The most dynamic large-scale seabed patterns are tidal sand waves, with wavelengths of several hundreds of meters, heights of several meters and migration rates up to tens of meters per year. Within this dynamic landscape, ecosystem engineering species have a large impact on both the hydrodynamics and the sediment dynamics. In order to understand this interaction, we followed a model approach. Additionally, field observations and flume experiments are executed to obtain input parameters and validation data for the model studies.