Benthic organisms, in particular bioturbators, can influence erosion processes either by affecting sediment roughness through their mere presence and/or activities, or by modulating sediment characteristics (e.g., silt content, granulometry), thus altering its erodibility. To date, it was not possible to distinguish the influence of bioturbating species on sediment roughness from their impact on sediment erodibility. Consequently, uncertainties remain regarding the role played by benthic species on sediment dynamics. In this study, we used a canal flume which allows to record the bed shear stress at the surface of a non-cohesive sediment (4% of mud) during erosion experiments, thus allowing to disentangle the influence of bioturbators, here the common cockle Cerastoderma edule, on the two erosion mechanisms. In order to assess the influence of bioturbators on sediment stability in different environmental situations, we additionally tested for the effects of three factors, i.e. bivalve density, availability of suspended food (i.e. phytoplankton presence) and microphytobenthos (MPB) occurrence, which may modulate the behavior of cockles. We observed that cockles promote the erosion of the sediment surficial layer by increasing its roughness as a consequence of their sediment reworking activity and/or presence at the sediment surface (emerging shell). In contrast, we calculated similar critical bed shear stress for erosion with and without bivalves suggesting that cockles have a minor influence on the erodibility of non-cohesive substrates with a low silt content. The destabilizing effect of cockles increased with the bivalve density whereas it was attenuated by the presence of phytoplankton. We hypothesize that the magnitude of cockles' bioturbation activity was lower when a high proportion of suspended food is available. High concentrations of suspended food may also have enhanced the filtration and biodeposition rates of cockles, thus rapidly leading to the ‘muddification’ of the sediment bed and consequently counteracting with the own destabilizing effect of the bivalves. Finally, the sole presence of MPB did not significantly affect the resuspension dynamics of non-cohesive sediments with a low proportion of mud.

底栖生物，特别是生物湍流器，可以通过仅仅通过它们的存在和/或活动来影响沉积物的粗糙度，或者通过调节沉积物的特性（例如泥沙含量，粒度）来影响侵蚀过程，从而改变其易蚀性。迄今为止，尚不可能将生物扰动物种对沉积物粗糙度的影响与其对沉积物易蚀性的影响区分开。因此，关于底栖生物在沉积物动力学中所起的作用仍然不确定。在这项研究中，我们使用了一条水道水槽，该水槽可以记录侵蚀实验过程中非粘性沉积物（占泥浆的4％）表面的床切应力，从而消除生物扰动器（这里是常见的蛤C皮）的影响前奏，关于两种侵蚀机制。为了评估生物扰动剂在不同环境条件下对沉积物稳定性的影响，我们另外测试了三个因素的影响，即双壳类密度，悬浮食物的可用性（即浮游植物的存在）和微底栖动物（MPB）的发生，这可能会调节鸟蛤的行为。我们观察到，由于鸟蛤的返工活动和/或存在于沉积物表面（涌出的壳），蛤通过增加其粗糙度来促进沉积物表层的侵蚀。相反，我们计算了在有和没有双壳类动物的情况下，相似的临界冲剪应力，表明鸟蛤对具有低淤泥含量的非粘性基质的可蚀性影响较小。鸟蛤的去稳定作用随双壳类密度的增加而增加，而浮游植物的存在减弱了鸟蛤的去稳定作用。我们假设当有大量的悬浮食品时，蛤的生物扰动活性会降低。高浓度的悬浮食品也可能提高了鸟蛤的过滤和生物沉积速率，从而迅速导致沉积床“泥化”，从而抵消了双壳类动物自身的破坏作用。最后，MPB的唯一存在并没有显着影响具有低泥浆比例的非粘性沉积物的重悬动力学。当有大量的悬浮食品时，生物扰动活性会降低。高浓度的悬浮食品也可能提高了鸟蛤的过滤和生物沉积速率，从而迅速导致沉积床“泥化”，从而抵消了双壳类动物自身的破坏作用。最后，MPB的唯一存在并没有显着影响具有低泥浆比例的非粘性沉积物的重悬动力学。当有大量的悬浮食品时，生物扰动活性会降低。高浓度的悬浮食品也可能提高了鸟蛤的过滤和生物沉积速率，从而迅速导致沉积床“泥化”，从而抵消了双壳类动物自身的破坏作用。最后，MPB的唯一存在并没有显着影响具有低泥浆比例的非粘性沉积物的重悬动力学。