Distribution of intertidal barnacles in Tokyo Bay

The distribution of intertidal barnacles was investigated at 558 sites in Tokyo Bay during 2004 and 2005. Ten species of barnacle were found in Tokyo Bay: Fistulobalanus albicostatus, Amphibalanus amphitrite, A. eburneus, A. improvisus, F. kondakovi, Balanus trigonus, Chthamalus challengeri, Tetraclita japonica, Megabalanus rosa, and M. volcano. Amphibalanus eburneus, A. improvisus, and F. kondakovi were found in the inner part of the bay, while T. japonica, M. rosa, and M. volcano appeared in the outer part of the bay. Fistulobalanus albicostatus, A. amphitrite, C. challengeri, and B. trigonus were found throughout the bay. Cluster analysis based on similarity of barnacle species composition classified the sites into two clusters, and Cluster 1 was further divided into three sub-groups. While Clusters 1 and 2 both consisted of sites in the outer part and inner part of the bay, Cluster 1 included sites exposed to open-shore conditions and Cluster 2 comprised sites on semi-sheltered shores. The distribution of the barnacles in the bay seems to depend on salinity at the macro scale, as between the inner bay and the outer part of the bay, but on wave exposure at the micro scale of less than several kilometers.