Abstract
Abstract. We present results from a series of laboratory experiments on a wave and current flume, where synchronous velocity and concentration measurements were acquired within arrays of rigid cylinders, representative of emergent vegetation and benthic communities, under different flow conditions. The density of an array of rigid cylinders protruding through a sandy bed affects the velocity field, sediment motion and resuspension thresholds when subjected to both unidirectional currents and regular waves. We compare the measured resuspension thresholds against predictions of sediment motion on non-obstructed flows over sandy beds. The results show that even if flow speeds are significantly reduced within the array, the coherent flow structures and turbulence generated within the array can enhance sediment resuspension depending on the population density.
Highlights
Aquatic vegetation and benthic populations alter their habitat in many different ways
Two species would be directly represented by the designed arrays (Fig. 1): (1) European fan worm (Sabella spallanzanii), a filter feeding tube worm that creates canopies of feeding fans over the sediment, generally found in shallow subtidal areas, and (2) Black mangrove (Avicennia germinans), a subtropical woody shrub found in salt marshes
Black mangrove, living in intertidal areas, forms a network of pneumatophores, protruding through the water surface to allow for root respiration (Houck and Neill, 2009), forming an array that shelters the sediment and organisms around it
Summary
Aquatic vegetation and benthic populations alter their habitat in many different ways. We focus our study on the case of sparse to dense, rigid, randomly distributed arrays of emergent (protruding through the water free surface) elements, with scales representative of populations of tube worms and rigid vegetation, such as mangrove roots. The European fan worm is considered as an ecosystem engineer, building large platforms on the sea floor, creating sheltering areas for other organisms to grow and live, trapping particles, blocking light, improving oxygen supply in the sediment, altering current velocities, and stabilizing/destabilizing the sediment within and around the patch (Wallentinus and Nyberg, 2007; van Hoey et al, 2008). Black mangrove, living in intertidal areas, forms a network of pneumatophores, protruding through the water surface to allow for root respiration (Houck and Neill, 2009), forming an array that shelters the sediment and organisms around it
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