Biogeomorphology: interactions between benthos and sediment dynamics University of Twente, Enschede, The Netherlands Deltares, Delft, The Netherlands Bas Borsje

Introduction Bio-geomorphology: interaction between benthos, water and sand Studying bio-geomorphodynamics offshore is important from an: Ecological perspective (conservation of biodiversity) Economic perspective (utilization of the seabed) 1-9

Biogeomorphological processes destabilising the top layer of the sediment by crawling filtering the fine sediment out of the water collumn stabilising the top layer of the sediment by covering adding roughness to the bottom redistributing the sediment 2-9

Field observations 3-9

Field observations 4-9

Modelling 5-9

Validation 6-9 Lower near bed velocity → Lower ripples (direct) → Deposition of fine sediment → Lower ripples (indirect)

7-9 Biogeomorphological interactions

Discussion Biota are able to influence the shape of the seabed The shape of the seabed is linked to the species habitat Understanding the coupled system is important Anthropogenic pressure will both influence sediment dynamics and biota directly and indirectly Windfarms Nourishments Dredging activities 8-9

9-9 Conclusions Biological and physical processes show a dynamic interaction Importance to account for bio-geomorphological interactions offshore Contact: Bas Borsje