A process-based model for erosion of Macoma balthica-affected mud beds

• Published in: Continental shelf research Vol. 31; no. 6; pp. 527 - 538
• Main Authors: van Prooijen, Bram C., Montserrat, Francesc, Herman, Peter M.J.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15.04.2011
• Subjects: Animals; Bioturbation; Density; Density distribution; Erosion; Erosion rate; Feeding; Macoma; Macoma balthica; Mathematical models; Mud beds; Process-based modeling; Sediment dynamics; Sediments; Willow; Bioturbation; Macoma balthica; Sediment dynamics; Process-based modeling; Mud beds; Erosion
• ISSN: 0278-4343; 1873-6955
• DOI: 10.1016/j.csr.2010.12.008

Modeling the effect of biota on sediment dynamics is a difficult task. In this paper we re-analyze experimental results of Willows et al. (1998) on the effects of Macoma balthica on sediment erosion. A process-based framework is proposed, fully compatible with a physical description of erosion processes in case of no biogenic influences. The bed is represented by a fluff layer on top of a substrate. A characteristic feature of the framework is that the sediment is represented by a probability density distribution for the critical shear stress, allowing for Type I and Type II erosion. M. balthica increases the sediment mass in the fluff layer. This increase is determined by considering the action radius, the overlap of feeding areas, and the feeding rate per animal. The calibrated action radius and feeding rate were in the range as found in the literature. The distribution of sediment over the erodibility classes and the erosion rate parameter are hardly influenced at all. Due to overlapping feeding areas, the effect is non-linear with density of the animals. The model results are in close agreement with the measured results, suggesting that no further formulations of biological effects are needed to simulate the experiments of Willows et al. (1998). In nature, other effects like disrupting the biofilm by grazing can be of importance and should be included in a later stage. This study emphasizes the crucial role of sediment availability and the effect of biota on it. This aspect needs more attention in future experiments. The proposed model turned out to work well for the effects of M. balthica and offers opportunities to include other biogenic effects in a process-based way as well. ► Process-based sediment transport models that include effects of biota are rare. ► A new process-based model with the effect of M. balthica on erosion is developed. ► M. balthica mainly increases the mass of the fluff top layer. ► The model offers opportunities to include effects of other species.