Spatial changes in the macrozoobenthic community structure at 27 tidal flats from the Sanriku Coast to the Yatsushiro Sea, Japan, using citizen-based monitoring data

The macrozoobenthos community structure was investigated at 27 tidal flats in Japan using citizen-based monitoring data. First, we compared the results of free surveys completed by citizens versus scientists conducted repeatedly at Ena, Bishamon, and Koajiro Bays, in the southern Miura Peninsula, and found that species numbers were comparable, although scientists found more deep-dwellers, symbionts, and habitat-specific taxa (e.g., muddy sediments, boulder zones, and reed marshes). Species richness showed no apparent latitudinal trends, whereas community structure had a geographical pattern from west to east, and could be grouped in clusters: A, tidal flats with reed marshes in the Yatsushiro Sea; B, Kii Peninsula; C, Koajiro Bay and open shores of the Yatsushiro Sea; D, Ena and Bishamon Bays; E, inner Tokyo and Ise Bays; and F and G, Tohoku region. The reed marshes in the Yatsushiro Sea hosted marsh-specific taxa, including endangered species, leading to specific community compositions at these sites. Species richness was greatest in Ena Bay (239 taxa in the citizen survey), mainly due to the high heterogeneity of habitat structure within a small spatial scale. Tidal flats in southern Miura Peninsula are valuable habitat for macrozoobenthos, including endangered taxa that are nearly extinct in the adjacent Tokyo Bay. Long-term monitoring of tidal flats is necessary for conserving faunal diversity and detecting the possible impacts of natural and anthropogenic disturbances and future climate changes in Japanese coastal waters.