Effects of Meretrix meretrix on sediment thresholds of erosion and deposition on an intertidal flat

Meretrix meretrix (M. meretrix) are commonly found on tidal flats along the global coast-lines. They are believed to potentially affect the sedimentary processes and thus morphological dynamics on the tidal flat. Their effects on sediment erosion and deposition, however, are not well quantitatively understood. To fill this gap, we conducted an integrated synchronous field investigation of hydrodynamic, sediment properties, and macrobenthos at two nearby tidal flats, one with abundant M. meretrix and the other without. In addition, seasonal comparison between summer and winter for the M. meretrix abundant site, where there was much less M. meretrix in winter than in summer, was conducted to further examine the influence of M. meretrix on critical value for the initiation of sediment entrainment. The results show that the critical shear stress for erosion (tau(e)) in the M. meretrix abundant site was lower than the bare tidal flat by similar to 23%. Differently, for the critical shear stress for deposition (tau(d)), the value at the M. meretrix abundant site was greater than that at the bare tidal flat by similar to 30%. Overall, we concluded that the existence of M. meretrix tends to enhance both the erodibility of the sea bed and the deposition of suspended sediment in the water column. It is suggested that the effect of macrobenthos on sediment erosion/deposition should not be neglected when predicting long-term morphological changes of an intertidal flat. (C) 2020 European Regional Centre for Ecohydrology of the Polish Academy of Sciences. Published by Elsevier B.V. All rights reserved.

Automated summary

Meretrix meretrix are commonly found on tidal flats worldwide and have the potential to affect morphological dynamics and sedimentary processes. Their impacts on sediment erosion and deposition are not well understood. A study showed that the presence of M. meretrix may increase sea bed erodibility and enhance deposition of suspended sediment in the water column.