Habitat structure and recent environmental changes in intertidal zones of Ena Bay, southern Miura Peninsula, Japan

The ecological characteristics of Ena Bay, southern Miura Peninsula, Japan, were reviewed as a preface for the feature article “Macrozoobenthos in Ena Bay, Miura Peninsula (Japan): a hotspot for benthic biodiversity retained at the mouth of highly urbanized Tokyo Bay” in the Japanese Journal of Benthology. We first demonstrate the ecological importance of ecotones retained in Ena Bay at the southern portion of the Miura Peninsula. The intertidal zones consist of reed marshes, sandy to muddy tidal flats, boulder zones, rocky shores, coastal forests, and seagrass beds, which support the high diversity of macroinvertebrates (356 taxa) in Ena Bay, which had been found in a citizen-based survey conducted from 2013 to 2022. Secondary, the ecological importance of the reed marsh is also discussed based on a citizen census of semi-terrestrial crabs, including the endangered taxa Chasmagnathus convexus, Orisarma intermedium, and Parasesarma tripectinis. Thirdly, the history of scientific research and conservation activities were also reviewed based on the literature and our activities. Finally, the changes in topography and habitat structure, mainly due to massive soil deposition from the catchment and erosion during storms, are discussed. We concluded that the biodiversity in Ena Bay is vulnerable to natural and anthropogenic disturbances, and attention is needed to assure the conservation of ecotones in southern Miura Peninsula.