Biogeomorphology: interactions between benthos and sediment dynamics

University of Twente, Enschede, The NetherlandsDeltares, 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)

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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

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Field observations

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Field observations

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Modelling

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Validation

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• Lower near bed velocity → Lower ripples (direct) → Deposition of fine sediment → Lower ripples (indirect)

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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

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Conclusions

• Biological and physical processes show a dynamic interaction

• Importance to account for bio-geomorphological interactions offshore

Contact:b.w.borsje@utwente.nl

Bas Borsje