瀬戸内海の島嶼部におけるベントスの機能群組成と地形的開放度を含む干潟環境の関係性

抄録

Shoreline topography is believed to affect the physical environment of tidal flats and composition of benthic animals. Different degrees of topographic openness on tidal flats are expected to alter the feeding modes and life forms of the benthic organisms that inhabit them. We investigated the distribution of tidal flat benthos, blow-off distance(Fetch)as topographical openness, grain size, and the elevation on tidal flats on islands in the Seto Inland Sea. In total, 135 macroscopic benthic animals were identified. Fetch was weakly correlated with the silt-clay content and elevation. Nonmetric multi-dimensional scaling(NMDS)ordering of species compositions with a frequency of occurrence of 5% enabled the construction of a two-dimensional plot of the NMDS related to with the fetch and the elevation. The median grain size, silt clay contents, and ignition loss also showed relationships with the plot, although the effective directions on the plot were different from those of the fetch and elevation. Deposit & Filter-feeding and epifaunal species were positively and negatively correlated, respectively, with the first axis. Filter-feeding and infaunal species were also positively and negatively correlated, respectively, with the first axis and were also correlated with the second axis. These relationships suggested that the Deposit & Filter-feeding and epifaunal species are more likely to occur on closed tidal flats characterized by finer grain sizes and higher organic contents. In addition, filter-feeding and infaunal species became more abundant as the grain size increased. Therefore, the topographic openness of tidal flats allowed us to predict the environments of tidal flats and the functional taxonomy type of dominant macrozoobenthos in their habitats.