MEPS 354:191-199 (2008)  -  DOI: https://doi.org/10.3354/meps07236

ABSTRACT: The role of physical processes in sediments in the response of macroinfauna remains largely unknown, in contrast to the role of waves and swash conditions. This study was motivated by our recent finding on the physics involved in intertidal sediments and aims to explore the link between geophysics and ecology. Field observations were performed on an intertidal sand flat on the east coast of Tokyo Bay, Japan. The results indicate that the development of suction (s), i.e. negative pore water pressure relative to atmospheric air pressure, was closely linked to the behaviour of the sand bubbler crab Scopimera globosa (Crustacea: Ocypodidae) and was the trigger responsible for the onset of its burrowing activity. Three series of laboratory burrowing experiments were performed by simulating the relevant geophysical environment prevailing in the intertidal flat sediment. The results demonstrate that the burrowing performance of S. globosa depended strongly on the state of s in association with the groundwater level. Notably, under a given sediment porosity, burrows started to develop and reached peak depth when s was present initially, but declined rapidly with increased s. The effective cohesion and stiffness of the sediment produced by the s were responsible for the manifestation of the threshold, optimum, and critical conditions for the development of the burrows. The present results imply that the s and related geophysical environmental conditions may have an important contribution to the natural selection of habitats of macroinfauna in intertidal zones.

KEY WORDS: Burrowing · Suction · Groundwater · Ocypodidae · Scopimera globosa · Laboratory experiments · Intertidal flat · Tokyo Bay