Tjitske Kooistra1*, Rob Witbaard1, Karline Soetaert1, Tjeerd Bouma1, Stuart Pearson2,3
1 Netherlands Institute for Sea Research (NIOZ)
The Dutch Wadden coast is, like many coastlines worldwide, threatened by erosion. To ensure coastal safety, currently regular beach and foreshore nourishments are applied. For maintaining the long-term sediment balance of the coastline and tidal basins, new nourishment techniques are being developed. In this context, a pilot nourishment of 5 million m3 sand was placed on the Ameland ebb-tidal delta. The project TRAILS (Tracking Ameland Inlet Living lab Sediment) aims to investigate transport pathways of the nourished sand within the ecological and social context. Since benthic fauna form a key link in the Wadden Sea ecosystem, and are strongly associated with their sediment habitat, their response to the nourishment cannot be overlooked. Therefore, we will dive into the far-field ecological implications of this ebb-tidal delta nourishment. Vice versa, fauna can alter sediment stability and composition by their activity or the structures they create, and hereby affect sand transport.
Using timeseries on benthic community composition from the ebb-tidal delta, subtidal and intertidal Wadden Sea, the temporal - seasonal and inter annual - variability of the benthic community will be quantified, to provide a context for effects of the nourishment. We will link benthic community composition to environmental gradients within the inlet system and map species sensitivity to sandification over the tidal basin. Additionally, we will investigate the bioengineering by benthic fauna through field, flume and mesocosm experiments. We will map bioturbation over the inlet system and experiment with bioturbators to determine their role in sand transport, reworking and the development of the nourishment. Physical structures such as bivalve shells can diminish bedload transport. To link this to community composition, we will test how shell shape and size affect sand transport in flume experiments. Interdisciplinary approached are developing in collaboration with the other work packages within the TRAILS project (modelling sand transport pathways and tracing sand using optically stimulated luminescence).
We will give an overview of objectives and approaches, and present preliminary results on the distribution of bivalve shells, and benthic community composition and variability over the tidal inlet.
Figure 1: Snapshots of the seafloor in the Ameland tidal inlet (own pictures).