A schematic diagram of interactive effects of tide and crab burrowing on the chemical properties of deep-layer and surface sediments. Tide with debris and litter flows into the crab burrow, increasing the total nitrogen (TN), total carbon (TC), total organic carbon (TOC) of deep soil; and crab excavation might promote the mineralization of soil organic matter and increase the total inorganic nitrogen (TIN) of surface sediments compared to the background soil without crab bioturbation. Crabs may repeatedly use the existing burrows, which incorporates the fallen litter and debris into excavated soil,resulting in more organic matter than background soil.