Geoenvironmental dynamics-benthic species distribution modelling for sandy beaches and sandy flats based on the ecohabitat chart and saturated-unsaturated seepage analysis

Recently, it has been demonstrated that the dynamics of suction, which represents the tension of moisture in sediments, play a pivotal role in controlling the geophysical environments of sandy beaches and sandy flats, and that there is a close linkage between the suction dynamics-induced variations of geophysical environments and diverse biological activities, yielding a range of geophysical environmental conditions that enable burrowing, burrow development, and physiological activity of Arthropoda, Mollusca, and Annelida species. Based on the cause-and-effect linkages, Sassa and Yang (2019a) developed an ecohabitat chart showing the critical geophysical environments for diverse macroinfauna inhabiting sandy beaches and sandy flats. In this study, the ecohabitat chart was upgraded by reflecting the geophysical environmental characteristics of nineteen sandy beaches and sandy flats, in Japan and South Korea, with diverse tidal ranges, sediment characteristics, and morphology, and by superimposing the optimal geophysical environment for the sand bubbler crab Scopimera globosa . An integrated platform for predicting and evaluating the coastal geoenvironmental dynamics-induced benthic species distributions was then developed by combining the upgraded ecohabitat chart and a saturated-unsaturated seepage analysis. The integrated platform was validated against the observed distribution changes of the four decapod crustacean, amphipod and isopod species, namely, S. globosa , Haustorioides japonicus , Trinorchestia trinitatis , and Excirolana chiltoni, caused by typhoon- and monsoonal storm-induced geomorphological changes in Gokahama sandy beach and Naha sandy flat, Japan. The developed integrated platform is expected to facilitate the assessment and evaluation of the benthic species’ responses to climate induced geoenvironmental changes as well as the geoenvironmental dynamics-based management in sandy beaches and sandy flats with significant differences in their characteristics. • We develop an integrated platform for assessing coastal geoenvironmental dynamics-induced benthic species distributions. • The platform consists of an ecohabitat chart and a saturated-unsaturated seepage analysis. • The chart shows the critical/optimal geophysical environments for the biological activities of diverse benthic species. • The platform accounts for events-induced distribution changes in four decapod, amphipod, and isopod species. • The platform helps the geoenvironmental dynamics-based management of sandy beaches/flats with diverse characteristics.