Investigation of the local and spatial roughness effects of oyster reefs and blue mussel beds

Direction Prof. Dr.-Ing. habil. Nils Goseberg
Execution Jan Hitzegrad, M.Sc.
Funding Federal Ministry of Education and Research (BMBF)
Duration 09/2019 - 08/2022
Project partner Institute of Structural Design (ITE) of the TU Braunschweig
Ludwig Franzius Institute of Hydraulic, Estuarine and Coastal Engineering of the Leibniz University Hannover
Senckenberg am Meer (Abteilung Meeresforschung)
smile consult GmbH
Journal Publications Hitzegrad, J., Brohmann, L., Pfennings, K., Hoffmann, T. K., Eilrich, A. K., Paul, M., Welzel, M., Schlurmann, T., Aberle, J., Wehrmann, A., Goseberg, N. (2022): Oyster Reef Surfaces in the Central Wadden Sea: Intra-Reef Classification and Comprehensive Statistical Description. Front. Mar. Sci. 9. doi: 10.3389/fmars.2022.808018

The German Wadden Sea has undergone significant changes in the last years due to the invasion of the Pacific oyster (Magallana gigas). Spreading from aquaculture farms, M. gigas has extended its spatial coverage throughout the German Beight most likely due to increased water temperatures as a result of climate change. Juvenile oysters require hard substrates to settle, which they found on blue mussel beds on the intertidal flats. As a result, Pacific oysters have replaced the formerly typical blue mussel beds as the pristine and predominant biogenic habitat. In contrast to the loose connections between the individual blue mussels, M. gigas form extremely strong bonds resulting in complex, rigid surface structures also referred to as oyster reefs.

Oyster reefs are highly resistant to mechanical stress including hydrodynamic loadings. Hence, it is hypothesized that the rough, rigid reef surfaces dampen waves and tidal currents due to frictional dissipation and can significantly reduce the wave energy reach-ing a shore. To date, very little research has been conducted on the inter-relation between oyster reefs and adjacent hydrodynamics. The overarching aim of the BIVA-WATT project is hence to understand the underlying processes involved and quantify the energy dissipation caused by oyster reefs.