S.M. Vaassen,1*, M.Z.M. Brückner2, M.G. Kleinhans1
1 Utrecht University
2 University of Exeter
Biostabilizers and bioturbators determine the shape of tidal morphology on different scales through their effects on flow and sediment erodibility. While previous research has mainly focused on the effect of these species small-scale morphology, we still lack understanding of how the species interact with their habitat and affect the morphology on the scale of entire tidal basins.
To better understand how contrasting species determine coastal morphology, we model the effects of the destabilising lugworm (Arenicola Marina) and a stabilising seagrass species (Zostera Noltii) on the morphology of a tidal basin. The domain was inspired by a Wadden Sea tidal basin. We use a novel numerical model that couples Delft 3D with a species code which accounts for growth and mortality of both species based on environmental parameters and competition (Brückner et al., 2019, 2021).
We found that the lugworm erodes the tidal flats and promotes sedimentation in the tidal channels, whereas seagrass increases the elevation of the tidal flat and promotes erosion of the tidal channels.
Figure 1: The distribution of Zostera Noltii (green) and Arenicola Marina (brown) overlain on the bathymetry of the tidal basin model domain (blue) for a scenario where competition between the two species is considered.
Figure 2: Cross-sections (A: x = 2000, y = 2500, B: x = 2500, y = 2800) of a tidal channel are shown next to the species fractions along these cross-sections. Where seagrass tends to promote erosion of the channel bed, lugworms initiate channel bed elevation.
Brückner, M. Z. M., Schwarz, C., van Dijk, W. M., van Oorschot, M., Douma, H., & Kleinhans, M. G. (2019). Salt Marsh Establishment and Eco-Engineering Effects in Dynamic Estuaries Determined by Species Growth and Mortality. Journal of Geo-physical Research: Earth Surface, 124 (12), 2962–2986.
Brückner, M. Z., Schwarz, C., Coco, G., Baar, A., Boechat Albernaz, M., & Kleinhans, M. G. (2021). Benthic species as mud patrol - modelled effects of bio-turbators and biofilms on large-scale estuarine mud and morphology. Earth Surface Processes and Landforms, 46 (6), 1128–1144.