抄録
The distributions of the species of sessile organisms settling on test plates immersed in the lower reaches of the Tomoe River in Shizuoka, Japan, was investigated during late summer in 2002. Sessile organisms settled actively from the mouth of the river to sites about 2 km upstream, while the settlement of fewer species was confirmed farther upstream at about 5 km from the mouth. The main species found settling on the test plates were the barnacles Fistulobalanus albicostatus and Amphibalanus amphitrite, and the polychaetes Hydroides elegans and Dexiospira foraminosa. Fistulobalanus albicostatus and H. elegans settled from the mouth all the way to 5 km upstream while D. foraminosa settled at only two sites about 2 km from the mouth. Cluster analysis conducted according to the dissimilarity of species composition among the 60 test plates classified the sessile organisms into six sub-communities. Near the mouth of the river, the communities were distributed mainly in the middle layer of the water column, while they were distributed among all layers at the sites 2 km upstream. Farther upstream, the communities were distributed in the bottom layers within the salt wedge and became sparse at the uppermost sites. The distributions of sessile organism species were strongly correlated with salinity in the lower reaches of this river.
